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Antigenics
Says Cancer Vaccine May Extend Survival-(Reuters-18/08/2003)
Biotechnology
company Antigenics Inc said that its experimental cancer vaccine improved
survival in 52 percent of advanced colon cancer patients who responded
to the drug in a small mid-stage clinical trial. Antigenics, based in
New York, said all of the 15 patients who responded immunologically to
the vaccine, called Oncophage, were alive two years after treatment, compared
with 50 percent of the 14 patients who did not respond. The disease-free
survival rate was 51 percent for responders and 8 percent for non-responders.
Typically, patients with advanced colon cancer can expect to live for
up to a year, said Garo Armen, chief executive of Antigenics. "These results
are not randomized, but in all the patients who showed an immune response,
there has been a trend toward benefit in our clinical trials," he said.
Oncophage
is a personalized vaccine derived from an individual patient's tumor.
Because the injected drug contains the patient's own genetic codes, it
is believed to be more effective in reprogramming the immune system to
attack the cancer without side effects. The vaccine is being studied in
a range of cancers, including kidney, pancreatic, skin and gastric cancers.
The first pivotal-stage data on Oncophage is expected later this year
with preliminary results from a Phase 3 kidney cancer trial, Armen said.
In that study, patients who have had their cancer surgically removed are
either being treated with the vaccine or simply observed, which is the
standard of care for patients with that stage of kidney cancer, the CEO
explained.
Initial
results will be compiled when 80 to 100 of the 600 or so participants
have had their cancer return, Armen said. Patients who do relapse are
then offered chemotherapy drugs or other toxic therapies. If the results
are promising, Antigenics would expect to file for U.S. Food and Drug
Administration approval of the vaccine in 2004, he added. "We are encouraged
with the collective data -- all pointing to the fact that there may be
efficacy," Armen said. Data from the 29-patient colon cancer study was
published in the Aug. 15 issue of Clinical Cancer Research.
[Top]
Adjuvant
5-FU for Colorectal Cancer Does Not Benefit Patients with High-Frequency
Microsatellite Instability-(ET-12/08/2003)
According
to results recently published in The New England Journal of Medicine,
a genetic mutation known as microsatellite instability affects responses
to the chemotherapy agent 5-fluorouracil (5-FU) in the adjuvant treatment
of colorectal cancer. Particularly, patients with high-frequency microsatellite
instability do not appear to derive any benefit from adjuvant treatment
with 5-FU. Colorectal cancer is the fourth most commonly diagnosed cancer
and the second leading cause of cancer deaths in the United States.
The
colon and rectum are parts of the body's digestive system and together
form a long, muscular tube called the large intestine. The colon is the
first 6 feet of the large intestine and the rectum is the last 8-10 inches.
If colorectal cancer is diagnosed in early stages, prior to the spread
of cancer from its site of origin, cure rates are high following the surgical
removal of the cancer. However, even at early diagnosis, some patients
remain at a high risk of experiencing a cancer recurrence, as some undetectable
cancer cells may remain in the body following surgery. Therefore, many
patients are offered chemotherapy following surgery (adjuvant chemotherapy)
in an attempt to kill any remaining cancer cells. Adjuvant chemotherapy
optimizes a patients chance for a cure. Cancers contain different genetic
mutations and researchers are now realizing that different genetic variables
affect how a cancer will respond to various therapies.
Microsatellite
instability (MSI) is a type of genetic mutation that occurs in approximately
15% of patients with colorectal cancer. Patients with this mutation can
have a high degree (high frequency) of MSI or a low degree (low frequency)
of MSI. Patients with no detectable MSI mutation are referred to as microsatellite
stable. Researchers determine the presence of MSI by taking cells collected
from the cancer and processing them with a laboratory test called polymerase
chain reaction (PCR) that is able to detect specific genetic mutations.
As determined through laboratory processes in tests involving the mixing
of cancer cells and specific agents, 5-FU does not appear to have anti-cancer
activity in colorectal cancer cells expressing high-frequency MSI mutations.
However, other chemotherapy agents, such as those known as topoisomerase
inhibitors, have demonstrated the capacity to kill colorectal cancer cells
with high-frequency MSI.
At
present, standard adjuvant therapy for colorectal cancer involves the
use of the chemotherapy agent 5-fluorouracil (5-FU). However, newer chemotherapy
agents have demonstrated anti-cancer activity in colorectal cancer and
are currently used in the treatment of more advanced colorectal cancers
or are being evaluated in clinical trials. As research involving genetics
and associated responses to treatment matures, standard practice will
undoubtedly become more individualized, enabling physicians to provide
specific treatment regimens matched with a patients genetic mutation(s)
to ensure optimal outcomes.
Researchers
from several institutions recently conducted a study in an attempt to
determine if patients with MSI responded differently to fluorouracil-based
chemotherapy. This study evaluated the outcomes of patients who had been
diagnosed with stages II-III colorectal cancer and had been participants
in 5 clinical trials between 1978 and 1988. All of these trials were direct
comparisons of adjuvant chemotherapy with 5-FU and leucovorin or levamisole,
versus no adjuvant therapy following surgery. From these data involving
570 patients, frozen specimens of their cancer were tested through PCR;
17% had high-frequency MSI, 10.5 had low-frequency MSI and nearly 73%
were microsatellite stable. Patients with low-frequency MSI or those who
were microsatellite stable had an improved cancer-free and overall survival
when treated with 5-FU-based therapy, compared to no adjuvant therapy.
Conversely, patients with high-frequency MSI derived no benefit in terms
of cancer-free and overall survival following treatment with 5-FU-based
adjuvant therapy, and even showed a slight decrease in survival when treated
with 5-FU-based chemotherapy, compared to no adjuvant therapy. For all
patients not treated with adjuvant chemotherapy, those with high-frequency
MSI had an improved long-term cancer-free and overall survival, compared
to those with low-frequency MSI or those who were microsatellite stable.
The
researchers concluded that patients with stages II and III colorectal
cancer with high-frequency MSI do not benefit from 5-FU-based adjuvant
chemotherapy. These results are consistent with laboratory results demonstrating
that 5-FU does not have anti-cancer activity in colorectal cancer cells
with high-frequency MSI. However, other chemotherapy agents that demonstrate
the capacity to kill colorectal cancer cells with high-frequency MSI in
the laboratory may be effective as adjuvant therapy in this group of patients.
The researchers caution that further clinical trials evaluating this issue
are necessary to confirm these results and possibly change the standard
of practice involving adjuvant chemotherapy in patients with stages II
and III colorectal cancer.
[Top]
Testing
for Colorectal Cancer: How Often Is Enough?-(HealthDayNews-01/07/2003)
Two
new studies come to very different conclusions on the proper timetable
for having sigmoidoscopy, the uncomfortable but effective test to screen
for cancer of the colon and rectum. American health officials currently
recommend that healthy people have a sigmoidoscopy every five years. But
a just-released study says there is, perhaps, a 1-in-100 chance that someone
who tested negative will develop a cancer, or an intestinal growth that
leads to cancer, within three years of the last exam. Yet another study,
using completely different methods, found that a single sigmoidoscopy
reduced the risk of undetected cancer for as long as 15 years, suggesting
the length of time between tests could be extended.Sigmoidoscopy
is the insertion of a flexible tube to inspect the lower portion of the
colon, where 60 percent of all colorectal cancers occur. The tube allows
doctors to look for polyps -- growths that can become cancerous. Most
people who have a sigmoidoscopy must take an enema, and there is a slight
risk that the intestine may be damaged.
The first study, done by Dr. Robert E. Schoen and colleagues at the University
of Pittsburgh Cancer Institute, included 11,583 people who had an initial
sigmoidoscopy and 9,317 who had a second examination three years later.
Of the second group, 1,292 of the people were found to have some sort
of intestinal growth in the second examination, says a report in the July
2 Journal of the American Medical Association. Follow-up exams of 951
of the people revealed that 72 had a precancerous polyp, and six had a
cancer. "Although the overall percentage with detected abnormalities is
modest, these data raise concern about the impact of a prolonged screening
interval after a negative examination," the researchers write in the journal.
The
other study, led by Polly A. Newcomb, director of prevention at the Fred
Hutchinson Cancer Research Institute in Seattle, collected information
on screening history and colorectal risk factors from 1,668 cancer patients
and 1,294 healthy people. There was a four-fold reduction in the incidence
of cancer in the distal region of the colon -- the part inspected during
sigmoidoscopy -- for people who recalled having at least one sigmoidoscopy,
compared to those who said they never had one. The reduction in cancer
lasted for at least 15 years, says the report in a recent issue of the
Journal of the National Cancer Institute. The University of Pittsburgh's
Schoen says the second study's conclusion is open to question because
it relied on potentially unreliable self-reporting to determine who had
had sigmoidoscopies. But Newcomb says "we have found that people can accurately
report if they have had a sigmoidoscopy." Newcomb says her study argues
for lengthening the recommended period between sigmoidoscopies. It takes
a long time for most polyps to become cancerous, she says. "The five-year
period recommended by organizations such as the American Cancer Society
doesn't appear to be data-based, unlike other recommendations," she contends.
Schoen,
who is an associate professor of medicine and epidemiology at the Pittsburgh
center, says he is not proposing a change in the five-year recommendation
"at this time." "We need more data," Schoen says, adding he'd like to
see what the cancer rate was five years after the first screening. "Maybe
it's not that different." Because of issues such as "cost, complications,
capacity [to do the testing], I don't think the results of [his] paper
should be interpreted as saying that everyone has to come back in three
years," Schoen says. But "it does look like the more screening, the less
the chance of missing something," he says.
[Top]
Obesity
Worsens Women's Colon Cancer Prognosis-(HealthDayNews-30/06/2003)
Obesity
raises the risk of death from colon cancer in women, but not men. That's
the surprising conclusion of a new study that found female colon cancer
patients can expect a much worse outcome if they're heavy, and perhaps
even a greater chance their tumors will return. But the study, reported
in the August issue of Cancer, found no such association in men, whose
outcomes were unaffected by their weight. Previous studies have found
obesity's impact on developing colon cancer and dying from it is stronger
in men than in women, says Eugenia Calle, an epidemiologist at the American
Cancer Society. "It's one of the most consistently observed gender differences,"
Calle adds. However, the latest work focused on people who'd already been
diagnosed with colon tumors, not the incidence of the disease in the general
population, which could help explain the difference. What's not in dispute
is the overall connection between weight and cancer.
Earlier
this year, Calle and her colleagues reported that overweight and obesity
could account for as many as one in seven cancer deaths among men, and
one in five among women, each year in the United States. Being overweight
increases blood levels of certain hormones and proteins, such as estrogen
and insulin, which can stimulate tumors. Weight affects the risk of cancers
in both sex-neutral organs, such as the esophagus, colon, liver and gallbladder,
as well as sex-specific sites such as the breast, ovaries, cervix in women
and the prostate gland in men.
In the latest study, Dr. Jeffrey Meyerhardt, of the Dana-Farber Cancer
Institute in Boston, and his colleagues looked at the link between body
mass index -- a ratio of height and weight -- and colon cancer in 3,759
men and women who'd been diagnosed with the disease. All the patients
were enrolled in a clinical trial of a now-common drug taken after surgery
to reduce the risk of relapse. Obese women -- those with a BMI was at
least 30 -- were about a third more likely than their normal-weight peers
to die within roughly nine years of starting the study. They also appeared
to be somewhat more likely to suffer relapses of their cancer, although
the study wasn't large enough to prove that. Weight wasn't a factor in
survival or return tumors for men, the researchers found.
For
patients of either gender, being overweight did seem to provide at least
one benefit. Obese patients were less likely than their thinner counterparts
to suffer serious side effects from their chemotherapy. Although many
cancer drugs are given in proportion to a patient's "ideal" weight, the
doses in the latest study were based on actual weight. The results therefore
suggest "that we should be treating patients doses based on their actual
body weight," Meyerhardt says. It's possible, he adds, that the fewer
side effects in the overweight patients is a signal that higher doses
of cancer drugs could be used safely and with better results.
Previous
research has hinted that women who gain significant amounts of weight
in the year after being diagnosed with breast cancer face a worse prognosis
than those who stay the same weight. Researchers at Dana-Farber are now
looking at whether the same phenomenon occurs in colon cancer patients.
Colorectal cancer will be diagnosed in more than 147,000 Americans this
year, and more than 57,000 will die from the disease, according to the
American Cancer Society.
[Top]
Nurses'
Night Shifts Linked with Colon Cancer-(Reuters-03/06/2003)
Sunshine
may be good for you, and nurses who work regular night shifts have a higher
risk of colon cancer, U.S. researchers reported. The study by researchers
at Harvard Medical School and Brigham and Women's Hospital in Boston supports
earlier research that found women who work night shifts have a higher
risk of breast cancer. "Because night-shift work has become very common
in developed countries, future studies should assess the relationship
of light exposure to the risk of other cancers and consider the risks
in men," they wrote in their report, published in the Journal of the National
Cancer Institute.
The
U.S. Bureau of Labor Statistics estimates that about four percent of adults
work rotating night shifts. Shift work disrupts normal melatonin production
and increases levels of other hormones such as estrogen. Women's cancers
are often linked with estrogen, but Dr. Eva Schernhammer, who led the
study, said melatonin may play a more important role. "While this finding
needs to be replicated in future studies, the data is beginning to show
that it may be melatonin, not estrogen, that is influencing cancer risk,"
she said in a statement. "If melatonin's anti-cancer properties are the
source of our observed effects, this research opens a whole new arena
of potential associations between exposure to light and a variety of cancers."
The
researchers studied 78,586 women taking part in a long-running program
called the Nurses' Health Study. The nurses who worked night shifts at
least three times a month for 15 years or more had a 35 percent greater
risk of colon or rectal cancer. Melatonin is produced at night and regular
exposure to sunlight affects the production cycle, which peaks in the
middle of the night. Artificial light suppresses melatonin production.
"Melatonin has well established anticarcinogenic properties, and a link
between exposure at night and cancer risk through the melatonin pathway
could offer one plausible explanation for the increased risk we observed,"
the researchers wrote. They noted, however, that they could be missing
something and urged further study.
[Top]
Genentech:
Colon Cancer Drug Extends Life-(Reuters-19/05/2003)
Genentech
Inc. said its experimental colon cancer drug, Avastin, extends life far
longer than it had expected, marking one of the biggest recent breakthroughs
in cancer research. Results of a late-stage trial show that the drug,
which slows tumor growth by cutting the supply of blood and oxygen, improved
survival when used in combination with chemotherapy. The news surprised
analysts and scientists, who had become skeptical of the approach, known
as anti-angiogenisis, after the drug had failed to prove effective in
treating breast cancer.
"Showing
a survival benefit is very rare," said Meirav Chovav, an analyst at UBS
Warburg. "This is going to transform the treatment of solid tumors, and
it's obviously going to transform Genentech." Avastin is the first of
a new class of drugs to treat cancer by inhibiting a protein known as
vascular endothelial growth factor, which plays an important role in stimulating
the growth of new blood vessels to tumors. By slowing the tumor's growth,
Avastin appears to help chemotherapy do its work of destroying malignant
cells. "This will give a huge boost to the anti-angiogenisis field, which
many scientific journals have been questioning lately," said Sapna Srivastava,
an analyst at ThinkEquity Partners.
Genentech
said the main side effect of Avastin is an increase in hypertension, or
high blood pressure. The company said there is also an increase in tearing
of the gastrointestinal tract. The company said this is uncommon. Patients
with colon cancer live on average 14 months from the time of diagnosis.
Genentech said it met the main goal of its trial, which analysts said
would likely be an extension of life by about two months. Since the results
are beyond Genentech's expectations, analysts said the drug could extend
life by about four months.
[Top]
Office
Rectal Exam for Colorectal Cancer Doubted-(Reuters Health-20/05/2003)
It's
an unpopular procedure for patients and doctors alike, and new research
suggests that office-based digital rectal exams aimed at detecting colorectal
cancers may not even be useful in spotting disease. Instead, researchers
advise skipping the in-office rectal examination, waiting instead for
a more thorough exam at the time of colonoscopy. "Now that colonoscopy
is routinely available, I think it's reasonable -- and I think many doctors
are actually already doing this -- not to stick with routine rectal examination
in the office," said Dr. Louise Langmead of the University of Sydney Concord
Hospital in Australia. She presented the findings here at Digestive Disease
Week, the largest annual gathering of gastroenterologists in the world.
In
a digital rectal exam, a gloved physician uses a finger to try to detect
suspicious growths in a non-sedated patient. While the procedure is usually
painless, for most patients "it's not a comfortable procedure -- it's
undignified," Langmead said in an interview with Reuters Health. Usually,
patients with symptoms suggestive of colorectal cancer will also receive
a digital rectal exam at the time of their colonoscopy, when they are
under sedation. When questioned, most of the patients in Langmead's study
said that, if given a choice, they would much prefer undergoing the digital
exam at that time, rather than while wide awake in their doctor's office.
So
how useful is the in-office rectal exam? In their study, Langmead and
her colleagues looked at the location of tumors in 68 patients with colonoscopy-confirmed
rectal cancers. One limitation of the digital rectal exam is that "it
is dependent on the length of the person's finger who performs it," Langmead
said. Her team judged the length of the average index finger to be roughly
7 centimeters (about 2.75 inches). Looking over the medical records of
the 68 patients, the researchers found that cancers in a full 45 were
located beyond that 7-centimeter range, meaning they would most likely
have been missed during a digital exam. Furthermore, factors such as the
presence of stool in the rectum mean that the test is generally assumed
to have about a 75 percent detection rate. All this means that, according
to the researchers' calculations, physicians would have to perform "280
rectal examinations to detect one cancer," Langmead said. "And this is
in patients who are going to have a rectal examination at the time of
their colonoscopy anyway." She points out there are no official guidelines
dictating that doctors perform these exams when looking for colorectal
cancers -- just "conventional wisdom" stemming from a period before the
advent of colonoscopy and other high-tech diagnostic tools. "I think patients
could be asked their opinion on it -- would they like to have it now or
would they like to wait until colonoscopy?," she said. "So my recommendation
would really be 'ask the patient'."
[Top]
Drinking
May Cause Rectal Cancer, Scientists Say-(Reuters-12/05/2003)
Drinking
large quantities of alcohol may increase the risk of rectal cancer, although
wine appears to be less of a threat than beer or spirits, scientists said.
"Regular drinkers significantly increase their risk of rectal cancer,
but that risk is reduced if wine makes up a third or more of weekly consumption,"
researchers from the National Institute of Public Health, in Copenhagen,
Denmark said. People who had more than 14 drinks per week of beer and
spirits, but no wine, were 3.5 times as likely to suffer rectal cancer
as non-drinkers, they wrote in the journal Gut. Those who drank just as
much alcohol, but a third of it in the form of wine, had a much smaller
increase in their risk.
The
authors said the benevolent effect of wine might be due to wine drinkers
having a healthier lifestyle, but it may also be because of a chemical
found in grapes that could protect against cancer. Previous research shows
that a chemical called resveratrol, found in grapes and wine, inhibits
tumor growth. The authors found no link between alcohol and cancer of
the colon, and said it was not clear why alcohol might cause cancer in
the rectum but not the colon. The authors could not be certain why alcohol
might cause rectal cancer, but suggested drinks could be contaminated
with cancer-causing compounds during production, or drinking may damage
the liver, inhibiting the breakdown of carcinogens. The findings are based
on a study which assessed weekly smoking and drinking habits of 15,491
men and 13,641 women aged 23-95 years old. The researchers also examined
other risk factors for colorectal cancer and followed up their patients
after 15 years. According to the World Health Organisation (WHO), colorectal
cancer is one of the most common cancers worldwide and accounts for 940,000
new cases every year and 500,000 deaths. The WHO suggests eating less
meat but more fruit and vegetables can reduce the risk of colorectal cancer.
[Top]
Big
Eaters May Live Longer with Colorectal Cancer-(Reuters Health-13/05/2003)
Despite
the dangers associated with a high-calorie diet, new research that people
who eat more calories live longer after a colorectal cancer diagnosis
than light eaters. However, eating a high-calorie diet has also been linked
to a higher risk of developing colorectal cancer in the first place, according
to study author Dr. Marie-Christine Boutron-Ruault. Although the reasons
behind these seemingly contradictory findings are not clear, Boutron-Ruault
said that she and her colleagues suspect that people who develop colorectal
cancer as a result of eating a high-calorie diet may have a form of the
disease that is less deadly than people who have cancer as a result of
other causes. "The main hypothesis is that the cancer due to this particular
risk factor -- here, high energy intake -- has a lesser malignant potential
than cancers due to other causes," Boutron-Ruault, based at the Institute
for Food and Nutrition in Paris, France, told Reuters Health.
Since
so much remains unknown, Boutron-Ruault cautioned that people should not
interpret these results to mean that eating too many calories is healthy,
even if they have colorectal or other cancers. "I would say that getting
a cancer is certainly not a good thing and that there are many studies
leading to the conclusion that high energy (intake) increases the risk
of cancer. It is too early to know if once the patient has got a cancer,
it is beneficial to have a high-energy diet," she said.
Colorectal
cancer is the second-deadliest form of the disease in the U.S., and only
approximately 45 percent of patients are alive five years after being
diagnosed. To determine whether calorie intake influences survival time,
Boutron-Ruault and her colleagues looked at an earlier study that recorded
148 patients' eating habits during the year before they were diagnosed
with colorectal cancer. The researchers then followed up with the patients
about 10 years after they underwent surgery. Reporting in the journal
Gut, the researchers found that people who ate the most calories -- from
carbohydrates, protein, or fat -- were more than 80 percent more likely
to be alive five years after a cancer diagnosis than people who ate the
least amount of calories. Boutron-Ruault noted in an interview that whether
patients were obese had no influence on their risk of dying. "Our findings
do not encourage (patients) to be obese to better survive colorectal cancer,"
she said. "What we hope will be the main consequence of our findings is
that medical doctors, especially oncologists, take some interest in the
nutritional status and the diet of their patients," Boutron-Ruault said.
She added that more research is needed to investigate the relationship
between post-diagnosis diet and cancer prognosis.
[Top]
Studies
Revive Colon Cancer Diet Theory-(AP-01/05/2003)
New research has revived the notion that a high-fiber diet may protect
against colon cancer. Long-standing recommendations for high-fiber diets
have taken a hit over the last few years after a handful of carefully
conducted studies failed to find a benefit. But experts say two major
studies published in The Lancet medical journal - one on Americans and
the other on Europeans - indicate previous research may not have examined
a broad enough range of fiber consumption or a wide enough variety of
fiber sources to show an effect. "These two new findings show that the
fiber hypothesis is still alive," said the leader of the American study,
Ulrike Peters of the U.S. National Cancer Institute.
Figuring
out the relationship between nutrition and disease has always proved difficult,
but experts say fiber is particularly complicated because there are various
types and they all could act differently. Fiber is found in fruits, vegetables
and whole grains. Americans eat about 16 grams a day, while Europeans
eat about 22 grams. The new studies indicate fiber intake needs to be
about 30 grams a day to protect against colon cancer. There are 2 grams
of fiber in a slice of whole meal bread. A banana has 3 grams and an apple
has 3.5 grams, the same as a cup of brown rice. Some super-high fiber
breakfast cereals have as much as 14 grams per half cup.
In
the American study, investigators compared the daily fiber intake of 3,600
people who had precancerous growths in the colon with that of around 34,000
people who did not. They were divided into five groups, according to how
much fiber they ate. The average roughage intake in the lowest group was
12 grams a day, while in the highest group it was 36 grams a day. People
who ate the most fiber had a 27 percent lower risk of precancerous growths
than those who ate the least. In the European study, the largest one ever
conducted on nutrition and cancer, scientists examined the link in more
than 500,000 people in 10 countries. As in the American study, questionnaires
separated the people into five groups, according to fiber intake. Following
them for an average of four years, 1,065 of them had developed colorectal
cancer. Those who ate the most fiber, about 35 grams a day, had about
a 40 percent lower risk of colorectal cancer compared with those who ate
the least, about 15 grams a day, the study found."In
the top quintile (group) they were eating 15 grams of cereal fiber, which
is equivalent to five or six slices of whole meal bread, plus they were
eating seven portions of fruit and vegetables a day, which is basically
the Mediterranean levels," said the study's leader, Sheila Bingham, head
of the diet and cancer group at Cambridge University's human nutrition
unit.
Discussions
about the link between fiber and bowel health - or, at least the relative
merits of white and brown bread - date back to antiquity. In a twist on
modern thought, Hippocrates, who lived in the 5th century B.C., believed
white bread was more nutritious because it creates less feces than brown
bread. Scientists now believe the extra feces is a benefit. The contemporary
theory that fiber wards off colon cancer began in the 1970s, when a British
doctor, Denis Burkitt, noted that poor people in Africa produce more feces
than Westerners and get much less colon cancer. One obvious difference
between the two groups was that Africans consumed more fiber. Scientists
believe that fiber dilutes and absorbs cancer-causing agents and makes
them flow more quickly through the body. Researchers have also theorized
that a high-fiber diet makes protective changes to cells or curtails bile
acids that irritate the intestinal lining and promote growths.
The
first big dent in the theory came in 1999 from a study that tracked the
eating habits of 88,757 American nurses for 16 years. The risk of colon
cancer was the same, regardless of how much fiber the women were eating.
Then in 2000, two studies which used a different method also came up negative.
They put people on different diets and counted precancerous growths in
their colons for up to four years. There was no apparent effect from high-fiber
diets or supplements. One major difference between the former and current
studies is that the new ones examine more diverse populations who eat
different types of fiber and in hugely varying amounts. However, Andy
Ness, a lecturer in epidemiology at Bristol University in England, who
was not connected with either study, said the latest research is not the
last word. "Across Europe, there is an amazing variation in risks of cancer.
There is also a huge variation in diet, so across these cultures you can
get this breadth of intake. However, what you might be picking up across
this range of diet is a range of cultures. It's possible it's something
else that goes with that pattern of diet," he said.
[Top]
Cancer
Strikes Blacks Harder than Whites-(HealthScoutNews-18/04/2003)
Despite
a substantial decrease in cancer among blacks over the last decade, this
racial group still has consistently higher rates of almost all cancers
than do whites, and their death rates are higher. Statistics comparing
incidences of colon, prostate, lung and breast cancers, the most common
cancers for both whites and blacks, show the latter group's chances of
developing certain types of cancer -- as well as dying from them -- are
much higher than whites, says Dr. Mark Clanton, first national vice president
of the national board of the American Cancer Society. "Prostate cancer
occurs in African-American men 60 percent more often than in white men,
and they die from it 1.3 times more often, and African-American women
have a 20 percent higher incidence rate of colon cancer and a 40 percent
higher mortality rate than do white women of the same ages," Clanton says.
Further, while the incidence of lung cancer among black men has decreased
1.6 percent annually since 1995, their chances of contracting lung cancer
are still 50 percent higher compared to the risk to white men. These are
among the sobering statistics released by the American Cancer Society
in its latest report on the incidence of cancer among the 37 million Americans
of black and Hispanic descent in the United States. The report is published
in conjunction with National Minority Cancer Awareness Week. "Even without
new advances in treatment and diagnosis of cancers, if we can engineer
among African-Americans a similar reduced rate of cancer as that of whites,
then tens of thousands of lives would be saved," Clanton says.
Dr.
Harry Harper, an oncologist at the Hackensack University Hospital Medical
Center, says oncologists are very aware of this discrepancy in cancer
incidence. "This information is out there among oncologists, but we haven't
really taken a global approach to the problem," he says. "This report
provides very helpful information so we can take the knowledge and start
to use it to reach out to the communities that haven't shared in the benefits
of cancer research and treatment." The report is not all bad news. The
overall incidence of cancer and mortality from the disease has dropped
by 1.2 percent a year since 1993 for blacks. For black men, in fact, the
drop in cancer rates was more than for white men during that same period,
2.1 percent a year versus 1.4 percent for white men. For black women,
there has been a 0.4 percent drop annually since 1991, compared to a 0.8
percent drop for white women.
Also,
five-year survival rates have also improved for blacks, more black women
are getting regular mammograms -- 67 percent now compared to only 30 percent
10 years ago -- and black men, though not women, are smoking less. But
these improvements still leave a huge gap between cancer rates for blacks
and whites, Clanton says, who points to economic disparities and lifestyle
differences between the two groups. While blacks make up only 12 percent
of the population, they account for a third of the poor in this country,
the report states. Twelve percent of blacks have no health insurance,
Clanton says, "which means they have considerably less access to screening
and prevention advice." Difficulty in geographical access to health care
and less education about the importance of early screening for cancers
are also factors, leading to later diagnoses of illness and thus lower
rates of survival from cancers, Clanton says. "Further, health-related
behavior may predispose African-Americans to increased cancer risk, with
smoking and exercise rates being the most important," Clanton says. "Exercise
is emerging as a powerful way to reduce cancer, diabetes and heart disease."
While
smoking rates between the two ethnic groups are not too dissimilar, black
men and women have lower rates of exercise than do whites -- 48 percent
of whites report engaging in regular, sustained exercise compared to 39
percent of blacks. In addition, blacks are heavier. In 2000, 77 percent
of black women were overweight, a jump from 59 percent in 1962. They also
have a higher rate of obesity than do whites -- 30 percent versus 20 percent,
according to the U.S. Centers for Disease Control and Prevention. Obesity
is associated with an increased risk for diabetes, heart disease and several
types of cancer including those of the breast, colon, uterus and esophagus.
Clanton says that focus on disparities in cancer incidences between racial
and ethnic groups is beginning to get the attention it deserves. "The
National Institutes of Health is creating a major focus on studying and
trying to understand these disparities," he says. "We have to equalize
the progress and improve the progress for the whole population."
[Top]
Treating
One Cancer May Beget Another-(HealthScoutNews-17/04/2003)
The
molecular action of a drug used to treat colon cancer might cause cancer
in other tissues, researchers report. That discovery calls for caution
in the search for other anticancer drugs with the same action, but it
is no cause for immediate concern, says Rudolf Jaenisch, a professor of
biology at the Massachusetts Institute of Technology's Whitehead Institute
for Biomedical Research. Jaenisch is the leader of the group reporting
the finding in Science. The drug is 5-azadeoxycytidine. It fights colon
cancer by reducing the activity of a simple molecule, methane, in the
cancer cells. Intricate animal studies now show this process, hypomethylation,
can cause leukemia, the journal paper says. Methane consists of one atom
of carbon and four atoms of hydrogen. It is found in a vast number of
organic chemicals, such as methyl alcohol. Inside a living cell, methyl
molecules attach themselves to DNA, the genetic molecule, turning genes
off or on. "It has been known for 30 years that cancer cells are hypomethylated,
but it has not been known whether this is cause or effect," Jaenisch says.
"We show that it is causal."
The
discovery is important because several drug companies are searching for
drugs that use the same mechanism as 5-azadeoxycytidine, which is very
toxic, Jaenisch says. The new drawback could affect the use of such a
drug, when and if it is found, he says. The finding was years in the making.
It started with a long effort by François Gaudet, a graduate student in
the lab, to develop a strain of mice with abnormal hypomethylation. When
that effort succeeded, it was found that 80 percent of those mice developed
an aggressive form of leukemia, which originates in the thymus. Amir Eden,
a postdoctoral fellow, then showed that hypomethylation speeded the development
of other forms of cancer in mice engineered to have those tumors. "There
seems to be a selective advantage for tumors to be hypomethylated, because
their chromosomes are more unstable," Jaenisch says.
It's
a fascinating discovery, says Dr. Stephen Baylin, a professor of medicine
in the Johns Hopkins University Oncology Center, but no reason to lose
one's head. "This is not something we should ignore, something to think
about, but I would caution against any suggestion that this would be a
problem in treating cancer," Baylin says. One important reason is the
finding was made in very young mice that were altered as embryos, he says.
"The study of tumors very early in the lifespan is very different from
blocking tumors later in adult life," he says. "We can't extrapolate these
results to what they would mean for treating cancers in adults, and probably
in children." Jaenisch plans to look at hypomethylation in other cancers,
such as those of the pancreas, breast and liver. Studying metabolic differences
in those tumors could lead to a better understanding of tumor formation,
he says.
[Top]
Screening
Interval for Colorectal Cancer Questioned-(HealthScoutNews-15/04/2003)
A
new study questions the recommended guidelines for a common colorectal
cancer screening procedure, and suggests the current five-year screening
interval may be excessive. The benefits of the procedure, called a sigmoidoscopy,
can last as long as 10 or even 15 years, the study researchers say. Almost
1 million cases of colorectal cancer are diagnosed worldwide each year.
Several effective tests are available that can detect the disease in its
earliest and most treatable stages, but little is known about how often
patients over 50 should undergo these screenings. Previous studies have
shown that precancerous tissue, called polyps, can take up to 15 years
to progress to cancer, suggesting that screening may not be necessary
as often as every five years. Researchers from the Fred Hutchinson Cancer
Research Center in Seattle looked at the efficacy of sigmoidoscopy screening
-- a procedure where a scope is used to examine the lower part of the
large bowel -- in reducing the incidence of colorectal cancer. They also
asked the question: How often should this test be used for the greatest
risk-to-benefit ratio?
The
study examined the screening history and colorectal risk factors of 1,668
patients between the ages of 20 and 75 living in Washington state. The
researchers compared the rate of colorectal cancer in this group to 1,294
healthy individuals within the same age range. The findings show those
who had received a screening sigmoidoscopy had a fourfold reduction in
the incidence of colorectal cancers compared with individuals who had
never had the procedure. Moreover, this benefit appeared to be sustained
for more than 15 years, indicating the recommended screening interval
is too aggressive. "If screening by sigmoidoscopy every 10 years was widely
adopted by adults over age 50, the incidence and mortality of colorectal
cancer could be substantially reduced," says Polly Newcomb, a researcher
at the Fred Hutchinson Cancer Research Center in Seattle and lead author
of the study, which appears in the Journal of the National Cancer Institute.Patients
don't like invasive screening procedures such as sigmoidoscopies and compliance
is an ongoing problem for physicians. Moreover, if the screening was recommended
once every 10 years, the reduction in usage would translate into significant
savings for the health-care system, the researchers argue.
But
Jack S. Mandel, chairman of epidemiology at Emory University's Rollins
School of Public Health, says the structure of the study may undermine
its findings. "There's a tendency for these types of studies to overstate
the benefits. We're trying to understand the precise magnitude of the
benefit [of sigmoidoscopy screening] and in this study there's uncertainty
in that benefit," he says. The number of individuals involved in some
of the study's analyses are so small that they could easily be distorted
by a mistake or classification error. Moreover, says Mandel, the study
looked at self-reported data that was not verified using patient records
to ensure that the subjects had really undergone screening sigmoidoscopy.
That bias tends not to be a problem because sigmoidoscopy isn't a procedure
that a patient is likely to forget, Newcomb says. People rarely confuse
it with other screening tests because the experience is unique from the
other available options, she says. Mandel argues a decision to lengthen
the recommended five-year sigmoidoscopy screening interval should be postponed
until more accurate data are available from a large randomized control
trial -- several of which are currently under way. Newcomb, however, cautions
results from those studies are unlikely to be available for another 10
years. In the meantime, the results of studies like this one are the next
best thing to a randomized control trial.
[Top]
Bowel
Cancer Screening Could Save Lives: Experts-(Reuters-31/03/2003)
British
medical experts predicted a sharp fall in deaths from bowel cancer by
2020 if the government introduces screening for the disease. "The biggest
step forward in the next decade is likely to be screening -- as a result
we will see the number of people dying from this disease fall dramatically,"
said Professor John Northover, one of Britain's top bowel cancer surgeons.
He said better diagnostic techniques, including powerful "finger-printing"
techniques will help doctors determine how a tumor will behave. "This
will allow us to do smaller operations without chemotherapy or radiotherapy
for the early low aggression tumors, while precisely targeting increasingly
powerful drugs at the more high aggression tumors," Northover, of St.
Mark's Hospital in London, added in a statement.
Bowel,
or colorectal, cancer is the second most common cause of cancer deaths
in men and women in Britain, but if the disease is diagnosed early, 80
percent can be successfully treated. Britain is considering introducing
screening and is looking at two types of tests to detect the disease.
One type of screen, fecal occult blood testing (FOBT), looks for blood
in the stool. During the other test being considered, flexible sigmoidoscopy,
a flexible probe with a camera on the end is used to look for benign growths
that can turn into cancer in the lower part of the bowel. Two-thirds of
all bowel cancers develop in this area. The government is analyzing results
from trials of the two types of tests. A spokesman for the Department
of Health said experts will be looking at which is the most clinically
effective, cost effective and how they will be implemented. "There are
a whole range of things that have to be decided," he told Reuters.
Dr.
Wendy Atkin, who is also at St. Mark's Hospital, said if screening is
introduced, the disease will be more treatable. "Currently only 40 percent
of patients survive for more than five years," she said in a statement.
The disease is more common in people 50 years and older. Bleeding from
the rectum or blood in the stool, diarrhea or constipation lasting more
than two weeks, pain, discomfort or a lump in the abdomen and unexplained
tiredness are symptoms of the illness. The latest figures from the charity
Cancer Research UK show that in 1999 there were 34,661 British cases of
bowel cancer.
[Top]
Blood Test May Predict Colon Cancer Risk-(Reuters
Health-13/03/2003)
A
simple blood test that looks for a certain genetic alteration may identify
people at risk of colorectal cancer, preliminary research suggests. The
blood test, still in the experimental stages, does not detect colorectal
cancer, but it may identify people who are likely to develop the disease
and who would benefit from additional screening, the study's lead author
told Reuters Health. "This is preliminary and needs to be confirmed by
more research," said Dr. Andrew P. Feinberg. "But we hope that it will
be possible to identify patients in the general population at risk of
cancer before they develop cancer." In an interview, Feinberg, who is
at Johns Hopkins University Medical School in Baltimore, Maryland, noted
that "we have made much progress" in identifying people who are at risk
of cardiovascular disease, such as those with high cholesterol. These
people can be treated early, even before disease develops. "We hope eventually
to do the same kind of thing for cancer," he said.
The
new blood test may identify people who should undergo more frequent screening
for colorectal cancer, according to Feinberg. On the other hand, he said,
people who have a low risk may be able to be screened less often. But
the researcher emphasized that "there is a lot of work that needs to be
done" to show that a person who tests positive on the blood test is more
likely to develop cancer in the future. He noted that the present study
looked at the risk of past or present cancer, but not the risk of cancer
in the future. And for the blood test to become practical, Feinberg said
that it needs to be refined and made easier and cheaper to perform.
The
test looks for "loss of imprinting" in the gene for a protein called insulin-like
growth factor II (IGF2). Imprinting marks on DNA tell whether a gene came
from the mother or the father. Previous research has shown that loss of
imprinting in the IGF2 gene occurs in about 30% of people with colorectal
cancer, compared with only 10% of people without the disease. To see whether
the loss of imprinting in this gene could be used to identify people at
risk of colorectal cancer, Feinberg used a DNA-based blood test to look
for the alteration in 172 people who were undergoing the cancer screen
colonoscopy. Loss of imprinting was much more common in people with a
family history of colon cancer and those who had the disease themselves,
Feinberg's team reports in the journal Science.
People
with a family history of the disease were about five times more likely
to have lost imprinting in the IGF2 gene. And people with a history of
growths called adenomas, which can become cancerous, were more than three
times more likely to have loss of imprinting than people with no history
of the growths. Loss of imprinting was almost 22 times more common in
people who had colorectal cancer or who'd had it in the past than in those
with no personal history of the disease. The study is "a step toward the
goal of developing a noninvasive test for detecting cancer," according
to Dr. David F. Ransohoff of the University of North Carolina at Chapel
Hill. In a related editorial, he, too, points out that the test does not
look for cancer itself, but a person's "tendency" to develop cancer. If
this test is sensitive enough, however, Ransohoff adds, it may be useful
in identifying people who can forego conventional cancer screening because
they have a low lifetime risk of colorectal cancer. Feinberg and a co-author
are entitled to a percentage of any royalties that Johns Hopkins may receive
through the sale of the technology used in the study. In addition, Feinberg
is a paid consultant to the German biotech company Epigenomics AG, which
has a licensing arrangement with the university.
[Top]
Colorectal
Cancer: A Potential Killer That Can Be Beaten-(HealthScoutNews-12/03/2003)
Colorectal
cancer is the second-leading cancer killer in the United States, claiming
more than 57,000 lives every year. Yet, the vast majority of these deaths
could be prevented. How? Through regular screening by a medical professional.
Because March is National Colorectal Cancer Awareness Month, 50 organizations
have joined forces to spread the message that screening measures -- plus
a healthy lifestyle -- can help stop this killer in its tracks. "People
are great procrastinators, [but] a screening test will help save your
life," says Dr. Sidney Winawer, co-chairman of the International Digestive
Cancer Alliance and a professor of medicine at Memorial Sloan-Kettering
Cancer Center in New York City.
While
lifestyle is important -- specifically, regular exercise combined with
a balanced, healthy diet that includes plenty of fruits and vegetables
and fewer animal fats -- screening is the proven key to prevention. Virtually
all colorectal cancers start as polyps, or abnormal growths, so the key
is to find the polyps before they turn malignant. "The National Polyp
Study, an Italian study and a University of Minnesota study have shown
that removing polyps prevents colon cancer," Winawer says. When it comes
to spotting potentially dangerous polyps, the technique of choice is the
colonoscopy, although other promising tools are under review. And Medicare
now pays for colonoscopies, an indication of just how seriously the medical
establishment is taking the issue of prevention and early diagnosis of
colorectal cancer.
New
guidelines issued in February by the U.S. Multisociety Task Force on Colorectal
Cancer state that all men and women over age 50 who have no symptoms and
no family history of colorectal cancer should have a colonoscopy. People
with a family history need to be screened starting at an earlier age.
The procedure, which usually takes half an hour and is done under mild
sedation, involves the insertion of a long, flexible tube with a camera
mounted on the end up through the rectum and on into the colon, or large
intestine. The camera takes pictures and transmits them outside the body.
Perhaps the best thing about a colonoscopy is that it's "one-stop shopping,"
says Winawer, lead author of the new guidelines. "You can do screening,
diagnosis and treatment by removing the polyps all in one examination,"
he adds. The downside of the procedure is the preparation, which involves
taking potent laxatives to make sure the colon is completely clear. "The
preparation is not pleasant, but I think it's a small price to pay for
one's life," Winawer says.
In
the future, patients may benefit from a "virtual colonoscopy," the procedure
newswoman Katie Couric underwent on the NBC "Today" show last March. Less
invasive than a conventional colonoscopy, a virtual colonoscopy uses a
computer assisted tomography (CAT) scanner to survey the colon from outside
the body. However, a virtual colonoscopy requires the same preparation
as a conventional colonoscopy, is not able to perform biopsies or remove
polyps, and may or may not be as effective as the traditional treatment.
"It's potentially promising, but we don't know how accurate it is yet,"
Winawer says.
Another
promising screening method under investigation is DNA testing that hunts
for genetic mutations in stool samples that might indicate the presence
of cancer or precancerous growths. "Right now, the pick-up rate [for spotting
cancerous polyps] is about 50 percent and it's a very complex laboratory
assay that's required," Winawer says. "It's not generally available nor
is it approved for general screening use." Taking a chapter from Fantastic
Voyage, researchers have also developed a tiny capsule containing a camera.
The capsule is swallowed as if it were a regular pill, then the camera
takes pictures as it travels through the digestive tract. The video transmittals
are relayed to doctors viewing a computer monitor on the outside. The
procedure is only FDA approved for the small intestine, which is located
above the large intestine. "It works well for the small bowel [small intestine],
but it doesn't work well for the colon [large intestine]," says Dr. David
Beck, chairman of the department of colon and rectal surgery at the Ochsner
Clinic Foundation in New Orleans. "It's not as good a picture of the colon
as the scope."
Again,
the miniature camera would not be able to perform a biopsy or remove a
troublesome growth. "You'd have to go back in, but that may be a way to
see who really needs a colonoscopy," says Dr. Michael Bouvet, a surgical
oncologist at the Rebecca and John Moores University of California San
Diego Cancer Center. "These are all not ready for prime time."
There
have also been advances even when screening does detect cancer. Surgery
to remove cancerous portions of the colon or rectum is still the primary
treatment. "If the cancer is caught early, it's very curable," Beck says.
"If the tumor is more advanced, we may add some additional things like
radiation or chemotherapy." If a tumor is found in the rectum, physicians
will often do chemotherapy to shrink the tumor before surgically removing
it. This is in an effort to preserve the sphincter at the entrance of
the rectum so the patient can continue with normal bowel movements, Bouvet
says. "The big message really is: Please don't wait for something like
this down the road," Winawer says. "Save your life today by going in for
a screening test that's available today."
[Top]
New
Mutation In Colorectal Cancer Gene Reported-(ET-28/02/2003)
A
newly discovered gene mutation that causes colorectal polyps and cancer
has been described in the New England Journal of Medicine (Vol.348, Number
9; 791-799). Although this is not a common mutation, its discovery is
another step forward in learning why some people develop this cancer.Almost
all researchers agree that most colorectal cancers begin as benign polyps
that slowly transform into cancer. They think this process takes about
10 years. Most of these polyps and cancers occur in people with no evidence
of a gene mutation. But, about 5 to 10% of colorectal cancers are caused
by known gene mutations.
There
are two major types of mutations. In the most common kind, called HNPCC,
a person forms a few polyps, which are benign growths. One or more of
these goes on to become cancer. The second kind of gene mutation is due
to a malfunction in the APC gene. People with mutations in this gene form
hundreds of polyps that inevitably transform into cancer. They must be
treated by removal of their entire colon. But many times, patients, along
with their family members, will have many polyps in their colon but no
gene abnormality can be found. It was these people who formed the basis
of this study. Oliver Sieber, BSc., Lara Lipton, MB, BS, and their colleagues
at the London Research Institute and in other European countries, examined
the genetic makeup of patients who had no known gene abnormality but had
multiple polyps. Some of them had developed cancer. One group was comprised
of people with fewer than 100 polyps, which is far less than APC gene
mutation carriers. A second group had more than 100 polyps, so they appeared
as if they might have an APC gene mutation, but didn't.
The
researchers found that about 30% of people who had more than 15 polyps
but less than 100 had a mutation in a gene called MYH. Of the people with
more than 100 polyps, 7.5% had a mutation in this gene. All these people
carried the mutation in both copies of the gene. A mutation may not cause
any problem if it occurs on only one copy of the gene. This kind of mutation
is called recessive. The researchers estimated that about 1% of us carry
a mutation on the MYH gene, but because we also have a normal MYH gene
we don't develop cancer - or do we? The researchers say that they can't
be sure that having even one copy of the mutation may not make someone
more susceptible to developing polyps and colorectal cancer. But according
to them, only studies of large numbers of people can answer this question.
Colorectal
cancer is the third most common cancer for men and women in the US (excluding
non-melanoma skin cancers) and the second leading cause of cancer deaths.
Nearly 150,000 people will be diagnosed with this cancer in 2003 and 57,000
people will die from it. Only lung cancer causes more cancer-related deaths
in the US.
[Top]
Western
Diet Ups Colon Cancer Risk in Women-(Reuters Health-11/02/03)
A
large new study has found that eating a diet rich in fruits and vegetables
may cut a woman's risk for colon cancer. However, the investigation found
no tie between diet and rectal cancer risk. Previous research has suggested
that diet plays a significant role in colon cancer, the third most common
cancer in the US, according to the American Cancer Society Web site. The
ACS estimates that about 105,500 new cases of colon cancer and 42,000
new cases of rectal cancer will be diagnosed this year. Dr. Teresa Fung
of the Harvard School of Public Health in Boston and colleagues analyzed
dietary patterns and the development of colorectal cancer in 76,402 women
aged 38 to 63 who were participating in the Nurses' Health Study.
During
the 12-year follow-up period, 445 of the women developed colon cancer
and 101 developed rectal cancer, the researchers note in the Archives
of Internal Medicine. Women who ate more processed and red meats, soda,
sweets, refined breads and high-fat dairy products-what the researchers
termed a "Western" diet--had a 46% increased risk for developing colon
cancer, compared to women who were consuming the least amount of foods
associated with a Western diet. Women who ate more foods that characterized
a "prudent" diet, including fruits, vegetables, whole grain products,
poultry and fish, were less likely to develop colon cancer, but the relationship
was not statistically significant. The study also did not identify a relationship
between diet and rectal cancer. "Our study provides further evidence that
switching from a typical Western diet to a more prudent diet may reduce
the risk of colon cancer," Fung and colleagues conclude.
[Top]
Traveler's
Diarrhea Bug May Help Treat Colon Cancer-(Reuters Health-10/02/03)
A
toxin released by the bacteria that cause traveler's diarrhea and chronic
diarrhea in developing countries may also slow the growth of colorectal
cancer, researchers said. The protective effect of the toxin from the
E. coli bacterium responsible for traveler's diarrhea may explain why
rates of colorectal cancer are lowest in countries with the highest rates
of infection with the bacteria, Dr. Stephen Carrithers of the University
of Kentucky in Lexington told Reuters Health. During the study, the researchers
used the toxin to slow the growth of a sample of laboratory-grown colorectal
cancer cells originally taken from a human patient. Eventually, doctors
may be able to use this bacterial toxin, known as ST, to treat or even
prevent colon cancer in patients, according to study author Dr. Scott
A. Waldman of Thomas Jefferson University in Philadelphia.
Waldman
told Reuters Health in an interview that small doses of the E. coli toxin
ST-- along with medications to prevent diarrhea--could help control the
spread of colorectal cancer cells in patients with cancer that has spread
throughout the body. Even if patients have only small polyps inside their
colons, he said, ST could help shrink those polyps, or perhaps even prevent
colorectal cancer in people who are at risk of the disease. "You can block
diarrhea, but still have the anti-proliferative effects. So that's important,"
study author Dr. GianMario Pitari, also of Thomas Jefferson University,
told Reuters Health.
ST
likely protects against colon cancer only while it is inside the body,
the authors noted--which suggests that people who suffered one bout of
traveler's diarrhea while abroad are no longer enjoying the anti-cancer
benefits of the toxin. Waldman added that the ST appears to only curb
the spread of colorectal cancer, so patients whose cancers are advanced
enough to spread to other parts of their bodies would likely have to use
other chemotherapy treatments as well. "This doesn't kill the cells, it
just makes them slow down," Waldman noted. Waldman and Pitari, along with
researchers at the Mayo Clinic in Rochester, Minnesota, published their
findings in the early edition of the journal Proceedings of the National
Academy of Sciences.
According
to Waldman, ST slows cancer growth by binding to a protein on the surface
of cancer cells. This stimulates the production of a substance that in
turn allows calcium to enter into the cell. The influx of calcium effectively
stops the cell from dividing. He added that the role of calcium in this
mechanism could help explain the observation that people who take calcium
have a lower risk of developing colorectal cancer. E. coli is present
in the US and other countries besides those marked by chronic diarrhea,
Waldman said. However, only certain strains of E. coli carry the genetic
material needed to produce the particular ST featured in the current report,
he added. Carrithers, who wrote a commentary accompanying the study, told
Reuters Health that previous research has suggested that this ST may also
kill colorectal cancer cells--not just slow them down. This suggests that
this treatment could eventually even rid some patients of the disease,
he said. He added that he agreed that the ST toxin holds promise for the
treatment of colorectal cancer, and is likely one that patients will embrace
if it is shown to be safe and effective in humans. "If the sacrifice is
for one to have occasional diarrhea yet prevent the (tumors) in the colon
from ever forming or progressing, it's worth it," Carrithers said.
[Top]
Know
the Risks for Colorectal Cancer-(HealthScoutNews-26/01/03)
Colorectal
cancer -- or cancer that begins in either the colon or the rectum -- is
the second-leading cancer killer in the United States. Like so many cancers,
this disease has both a genetic and a lifestyle component. Here are some
common risk factors: · If you have parents or siblings who have had colorectal
cancer, you are more likely to develop it yourself. · Women who have had
ovarian, uterine or breast cancer are also at a higher risk, as are men
and women who have already had colorectal cancer. · Although research
continues into possible behavioral factors, diets that are high in fat
and calories and low in fiber seem to be likely culprits. · The disease
is much more common in people over the age of 50.
The
good news is that the disease is almost entirely preventable. Most colon
or rectal cancers start as small polyps, or benign growths on the inner
wall of the colon and rectum. Detecting and removing these polyps soon
after they appear can prevent most cases of colorectal cancer. Talk to
your doctor about a regular screening program. In general, the American
Cancer Society recommends that screening start at age 50. People have
different options, but the one preferred by the cancer society is a fecal
occult blood test (FOBT) once a year and flexible sigmoidoscopy every
five years. You could also opt to have a colonoscopy every 10 years. A
sigmoidoscope is a lighted tube about the thickness of a finger that's
inserted into the lower colon via the rectum. A colonoscope is basically
a longer sigmoidoscope.
[Top]
Blood
Sausage May Hinder Colon Cancer Testing-(Reuters Health-20/12/2002)
People
with a hankering for black pudding should abstain while they're being
screened for colorectal cancer, British researchers advise, as the congealed
pig's blood in the British delicacy can interfere with screening tests
used to identify blood in the stool. In the British Medical Journal's
holiday issue, traditionally a repository of the more entertaining sort
of evidence-based medicine, Dr. Neil Haslam and colleagues conducted a
rigorous study into the effect of eating blood sausage on fecal occult
blood testing, also called Haemoccult testing. They conducted their study
in Bury, "black pudding capital of the world," although they note that
variations on the blood sausage theme are also served in Germany, France
and Spain.
The
British version is made of congealed pigs' blood, fat, and rusks, or sweetened
bread crusts, contained in a piece of intestine. The 10 participants under
the age of 35 completed a Haemoccult test, requiring six stool samples
taken over three consecutive days. "Participants then eagerly ate a locally
produced 7-ounce black pudding and then had a further Haemoccult test,"
they write. A positive test result was defined as the occurrence of one
or more positive specimens from the six provided.
Initially
all volunteers returned negative tests, but after consumption of black
pudding, four people tested positive. The researchers then questioned
100 people about their black pudding consumption and found that 63% succumbed
on occasions, 8% weekly. In Bury, the numbers eating the "almost irresistible"
delicacy would mean a doubling of the proportion of people who would test
positive for fecal occult blood, the researchers calculate. "Gourmets
should be advised to avoid black pudding during screening for fecal occult
blood," they conclude. The research team reports no external funding,
however they do note under the heading of competing interests: "NH is
extremely fond of black pudding".
[Top]
Fiber
Overload Won't Stop Recurring Colon Polyps-(HealthScoutNews-05/11/2002)
Don't
toss your All-Bran yet, but new research shows that fiber intake did not
affect the recurrence rate of colon polyps. All the participants entering
the trial were already consuming higher-than-average amounts of fiber,
however, which may have skewed the results. "Because they were already
consuming fiber, they may already have been protected," says Elizabeth
Jacobs, lead author of the study appearing in the Journal of the National
Cancer Institute.
Colon
cancer, the second biggest cancer killer in the United States, starts
with tiny polyps in the colon. Plenty of evidence suggests that the cancer
is at least partially caused by environmental factors. And anecdotal evidence
suggests that high-fiber diets may protect against the cancer. This research
examined data from the Wheat Bran Fiber (WBF) trial, which looked at about
1,500 men and women in the Phoenix area, all of whom had had at least
one colorectal adenoma removed within the past three months. Adenomas
or adenomatous polyps are abnormal growths in the colon that are generally
thought to be precursors to cancer. The participants had been randomly
assigned to receive a cereal fiber supplement of either two grams per
day or 13.5 grams a day. After three years, there appeared to be no difference
in recurrence rates between the two groups.
The
participants were then divided into four groups according to how much
fiber they were eating when they joined the trial. Here, again, baseline
fiber intake did not affect adenoma recurrence between the groups or within
the groups. Nor did the source of dietary fiber (fruits; breads, cereals
and crackers; and vegetables) at baseline seem to have any effect on polyp
recurrence. It's difficult to draw any firm conclusions from the results
because the men and women studied were already consuming more fiber than
your average American (17.5 grams per day vs. 14.8 grams per day). "This
only represents three years and since the participants already may have
eaten more fiber, all we know is that three years of supplementation did
not work," Jacobs says.
"In
the world of polyps, three years is probably not long enough, biologically,
to expect any real results," says Dr. Irwin Grosman, chief of gastroenterology
at Long Island College Hospital in Brooklyn, N.Y. The ideal study, Jacobs
adds, would look at what people eat through their entire lives, because
it takes at least 10 to 20 years for colorectal cancer to develop. Such
a study, however, is unlikely to occur. Another important area for research
is to determine where intake is most important: for prevention or to slow
down growth rates of the polyps. Still, Jacobs says, none of this means
you should stop eating fiber, especially given that it seems to have beneficial
effects on other aspects of health, such as heart disease and diabetes.
[Top]
Unstable
Chromosomes Could Kick Off Colon Cancer-(Reuters Health-18/11/2002)
A
mutation in a gene called APC is believed to be present in most cases
of colorectal cancer, but new research raises the possibility that a defective
APC gene may not be the first step on the road to cancer. According to
a mathematical model created by Dr. Christoph Lengauer of Johns Hopkins
University in Baltimore, Maryland and colleagues, it is possible that
unstable chromosomes may trigger changes in the APC gene that lead to
cancer. In an interview with Reuters Health, Lengauer stressed that the
idea is only a possibility and still needs to be proven. What comes first,
APC mutations or chromosomal instability, is a bit a "chicken or the egg"
question, he said. Unlike that age-old question, though, determining whether
changes in APC or unstable chromosomes come first could have important
implications for cancer therapy, according to Lengauer. Documenting the
first step in colorectal cancer, he said, will give scientists a target
for developing new treatments to destroy cancer in its earliest stages,
before it has a chance to spread.
In
the interview, Lengauer explained that about 85% of the time, the APC
gene is defective in colorectal cancer. This gene helps regulate the growth
of cells, so if it is not working properly, cancer cells can grow unchecked.
Most cases of colorectal cancer also involve another type of chromosomal
defect, Lengauer said, in which the rate at which chromosomes are lost
and gained is increased. The Johns Hopkins researcher noted, however,
that it has been uncertain whether this chromosomal instability is a result
of an APC mutation or itself triggers such a genetic defect. The question
still awaits a conclusive answer, but it is possible that chromosomal
instability could come first, Lengauer's team asserts in a report in the
journal Proceedings of the National Academy of Sciences. The authors developed
a mathematical model suggesting that genetic mutations that cause chromosomal
instability could develop before APC mutation occurs.
To
develop new therapies for colorectal cancer, it is important to know what
the earliest steps in the cancer process are, Lengauer said. If changes
in APC come first, then it might be possible to develop a drug to prevent
those changes, he said. Alternately, a drug that keeps chromosomes stable
might stave off cancer if chromosomal instability is the initial step
in colorectal cancer, according to Lengauer. The model does not prove
that chromosomal instability is the first step, but it does give researchers
a starting point, he said. To see if unstable chromosomes are indeed the
"driving force" behind colorectal cancer, Lengauer and his colleagues
plan to look for chromosomal instability in the earliest forms of precancerous
growths called adenomas. Finding chromosomal instability in these growths
would support the idea that chromosomal instability is the instigator
of colorectal cancer, he said.
[Top]
Common
Virus May be Linked to Colorectal Cancer-HealthScoutNews-15/11/2002)
A
virus that lurks harmlessly in the bodies of tens of millions of Americans
may play a role in the development of colorectal cancer, new research
suggests. The findings are preliminary, and the germ -- known as human
cytomegalovirus -- might not actually contribute to the development of
the second deadliest type of cancer, says study co-author Dr. Charles
S. Cobbs, a neurosurgeon at the Birmingham VA Medical Center in Alabama.
"But if other people can confirm this data, then the plot thickens," he
says.
Colorectal
cancer is "notoriously difficult to treat," Cobbs says, especially if
it spreads to other organs such as the liver. An estimated 148,300 cases
will be diagnosed this year, and the disease will kill approximately 56,600
Americans, according to the American Cancer Society. Among all cancers,
only lung cancer takes more lives. Colorectal cancer typically strikes
people over the age of 50. Screening tests are available, and experts
estimate that they could detect and prevent 90 percent of the cases. Cobbs
says his investigation into colorectal cancer was inspired by his previous
research into the possible role that human cytomegalovirus (CMV) could
play in brain tumors.
CMV
is a type of herpes virus, a member of the same family of germs that cause
cold sores, genital herpes, chicken pox, some kinds of mononucleosis and
Epstein-Barr virus. An estimated 40 percent of the U.S. population has
been infected with CMV, says Frank Myers, an epidemiologist with Scripps
Mercy Hospital in San Diego. However, except for infants, who can be especially
vulnerable, the virus almost never causes symptoms. "It's thought to lie
around latent in the body and not do anything," Cobbs says. The exceptions
are people with weak immune systems, such as AIDS patients, and those
who are on special drugs because of organ transplants. CMV is extremely
common in Third World countries, where close to 100 percent of the population
may be infected. The virus is transmitted through saliva and urine, Myers
says. Breastfeeding can transmit the disease, says Cobbs, and so can sex.
Gay men are especially at high risk.
In
his previous research, Cobbs found signs of CMV in almost every brain
tumor he examined. Studies from the 19 |
