Selenium: New entry in fight against prostate cancer
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DOCTOR Q&A: |
Read what doctors say about the symptoms of prostate cancer or ask your own questions.
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June 17, 1999
Web posted at: 1:44 p.m. EDT (1744 GMT)
By Senior Medical Correspondent Dan Rutz
(CNN) -- Evidence is mounting that
selenium, a little-known trace element,
can help protect against one of the
most common cancers in men.
Researchers at the University of
Arizona have shown in preliminary
studies that daily selenium
supplements cut the rate of prostate
cancer by more than half. Now, new
research is under way to see if selenium might also help those who already have
prostate cancer.
The Rev. Lester Plattner,
diagnosed three years ago, decided
against surgery or other radical
treatment. "I just didn't want to go
through a series of shots and through
radiation and anything like that," he said. "And if
the Lord wants me, he knows where I'm
at, and he can get me anytime he wants
me."
It is not unusual for men Plattner's
age, 79, to forgo treatment for prostate
tumors. Typically, such cancers
diagnosed after age 70 are
slow-growing. Proponents of what
doctors call "watchful waiting" reason
that many older men are likely to
die of other causes before their cancer
ever poses a threat.
But Plattner is very much
interested in improving the odds. As
part of the "Watchful Waiting with
Selenium" study, he is among 260 men
helping researchers find whether
selenium delays progression of prostate
cancer. The volunteers are
randomly prescribed one of four
selenium dosages, or a placebo "dummy"
pill, and are to be closely monitored
for the five years.
"I don't know
whether I'm taking the pill or whether
I'm taking sugar" says Plattner. "This is my contribution to society."
Through patient interviews,
examinations and blood tests measuring
PSA -- an indicator of prostate cancer
progression -- scientists will document
any side effects, good or bad, of
prolonged selenium use and any
differences in the rate of cancer growth across the five groups.
Larry Clark, Ph.D., directs the
selenium and cancer projects at the
University of Arizona Cancer Center.
He was in charge of a landmark 10-year
study showing the incidence of
prostate cancer was 63 percent less among
those taking daily selenium
supplements.
"We've gone from knowing
almost nothing about diet and prostate
cancer to prostate cancer being the
leading cancer that may be affected by
diet, meaning we can do the most to
prevent it if we find the right diet,"
Clark said. He points out that the same
study showed selenium users had markedly less lung and colorectal
cancer as well. More than a thousand
men volunteered for the trial. The
study, published in December 1996,
caught the attention of many cancer
researchers interested in the role diet
and nutrition might play in preventing
cancer. Suddenly, Clark says, he had
company in his selenium research.
"I
think it was a surprise for everyone
that selenium would have such a major
effect on the prostate," he said.
Since then scientists have been looking
for possible explanations for
selenium's apparent good effects.
Clark cites a recent report describing
a specific type of protein within the
prostate that is very responsive to
selenium intake. "This
probably helps protect against
oxidative damage there in the prostate."
Selenium is a trace element found
to a varying extent in soil. It enters
the human diet through plants such as corn and through the meat of animals grazing on
vegetation containing selenium.
Products from selenium-rich soils of
the Plains and Mountain States carry
proportionately more selenium than
those coming from the Upper Midwest,
Northeast, and Florida, where selenium
soil concentration is low. Grains
(especially from the Great Plains),
fish, organ meats and Brazil nuts tend
to be high in selenium. It is often
included in broad-spectrum nutritional
supplements. There is no official
government nutritional guideline on
selenium. Typical recommendations range from 70 to 200 micrograms a day.
Doctors at Columbia University in
New York are also looking into
selenium, as well as other nutritional
supplements, for preventing and treating
prostate cancer. The work is part of
the University's Center for Holistic
Urology.
A four-year study is under way to see
whether a low-fat, high-fiber diet with
soy supplementation helps prevent a
recurrence of prostate cancer in men
who've been treated previously. The study is following 100 men who
their
cancerous prostates removed surgically but whose cancer
was advanced enough at the time of
surgery to leave them at higher than
average risk of relapse.
Dr. Aaron
Katz, director of the center, sees
great value in the research. "Currently there is no consensus as to
the optimal therapy for those patients
who've had radical prostatectomy and
who are at high risk for a return of
their prostate cancer." Katz favors
research that might help reduce
dependence on radiation and hormone
therapy, which often cause unpleasant
or dangerous side effects. "We need
more options to treat patients with
prostate cancer," he says in a release issued by Columbia Presbyterian Center.
"Some patients aren't good candidates
for current therapy strategies. Plus
recent studies suggest that diet may
play an important role in the
development and recurrence of prostate
cancer."
Katz says he's especially excited
by the possibility of treating advanced
prostate cancer with a combination of
Chinese herbs. In a small study of men
who had exhausted all conventional
treatments for their cancers, the
herbal cocktail called "PC-SPES"
brought significant improvement for
85 percent.
Five percent of the subjects developed
potentially dangerous blood clots in
the legs, leading doctors to prescribe
aspirin and other anti-clot medications. Despite the
side effects, Katz said, the herbal therapy shows
promise as a possible cancer treatment
and deserves further study.
Laboratory studies attribute a potent
anti-cancer effect to PC-SPES in both
test tube and animal experiments, he adds.
Katz says details of the study have
been accepted for publication in the
British Journal of Urology, although
many of his colleagues remain
unimpressed. "They think it is a bunch
of hokeypokey, " he says. "So
did I until I started getting into it."
Those involved in nutritional
cancer research say diet supplements should not take the place of regular
checkups. The American Cancer Society
recommends annual physical examination
of the prostate and a PSA blood test
starting at age 50. Men with a family
history of prostate cancer and others
at high risk, including all African- American men, are advised to begin
prostate screening at age 45 or earlier
depending on individual risk factors.
RELATED STORIES:
Study: Mineral selenium cuts risk of prostate cancer August 22, 1998
Vitamin supplement may help prevent prostate cancer May 19, 1997
Selenium may lower several cancer risks December 24, 1996
In-Depth: Mineral guide
RELATED SITES:
New York Presbyterian Hospital: The University Hospital of Columbia and Cornell
NCI's CancerNet
Dr. Larry C. Clark, University of Arizona
University of Michigan: Prostate Cancer
American Cancer Society
Vitamin E and prostate cancer - A Mayo perspective
American Society of Clinical Oncology
PC SPES: Alternative Prostate Discussion Group
PC-SPES
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