back
|
 |
Prostate
cancer's natural enemy?
By
Shari Roan
Los Angeles Times,
June 2, 2003
Because
prostate cancer is typically a slow-growing disease that occurs late in
life, doctors sometimes advise men older than 65 to simply monitor the
illness. This approach, called "watchful waiting," leaves many
men feeling frustrated and helpless.
Now, researchers at UC Davis Medical Center have found that a component of
soy, called genistein, appears to inhibit prostate cancer growth. If
genistein proves effective in large-scale trials, it would not only fight
the tumor, it would make men feel as if they were actively managing the
disease.
The supplement, available without a prescription, has been a popular
therapy for prostate cancer in Asia for many decades and is often used by
American men with the disease.
In a UC Davis study of prostate cancer patients who had been assigned to
watchful waiting, 62% (eight of 13) lowered their levels of
prostate-specific antigen, or PSA, after taking large doses of genistein
for six months. (PSA is a blood marker for prostate cancer.) The men's PSA
levels were lowered by 3% to 61%; three of the men dropped out of the
study after experiencing diarrhea.
However, researchers found that genistein made no difference in a second
group of men who had already had surgery, radiation or hormone therapy. In
that group, only one among 46 patients had a lower PSA after taking
genistein.
All 62 patients in the study were given five grams of genistein daily for
six months.
"Half of people on watchful waiting go on to active treatment [such
as surgery or radiation] within a couple of years. They just can't stand
doing nothing but watching their PSA," says Dr. Ralph deVere White,
director of the UC Davis Cancer Center and the lead author of the study.
"If we can lower your PSA during watchful waiting, we may really
spare people treatment for a longer period of time."
Treatment such as surgery or hormone therapy is often required when
prostate cancer is larger and more aggressive, but they can cause
impotency.
The research findings, presented in April at the annual American
Urological Assn. meeting, can only be considered preliminary because the
study was small, DeVere White notes.
"We can't ignore this result," says DeVere White. "But we
do need to do another study." In the next study, still in the
planning stages, a much larger group of untreated prostate cancer patients
will receive either genistein or a placebo, he said.
UC Davis researchers have been studying genistein largely because people
living in Asia consume a lot of soy and have lower rates of certain types
of cancer, such as prostate cancer. The researchers demonstrated in 2001
that the compound caused prostate cancer cells in the lab to die and
slowed prostate cancer growth in mice. Studies suggest that it helps
control cell growth.
Lowering male hormones, such as testosterone, is sometimes used as a
therapy to control prostate cancer. But genistein does not appear to work
that way. Nor does it have estrogen-related side effects, such as breast
enlargement. Even large doses appear safe. The diarrhea may have been
caused by the material used to form the capsule, DeVere White says.
Researchers aren't sure why the compound appears ineffective in men who
already have had some type of treatment, although it could be because of
the amount of genistein reaching the prostate.
"Our hypothesis is these men [on watchful waiting] have normal blood
supply to their prostate," he says. "If you look at someone who
had radiation therapy to the prostate, you've interfered with blood
supply. The question is: Does the genistein get into the cells?"
In the future, researchers want to study whether healthy men can take
genistein to prevent prostate cancer.
Copyright
© 2002 Global Action on Aging
Terms of Use | Privacy
Policy | Contact Us
|
