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The exact cause of prostate cancer is not known, so at this
time it is not possible to prevent most cases of the disease. Many risk
factors such as age, race, and family history cannot be controlled. But
based on what we do know, some cases might be prevented.
Diet
You may be able to reduce your risk of prostate cancer by
changing the way you eat, but the results of research studies are not
yet clear.
The American Cancer Society recommends choosing foods and
beverages in amounts that help achieve and maintain a healthy weight,
eating a variety of healthful foods with an emphasis on plant sources,
and limiting your intake of red meats, especially high-fat or processed
meats. Eat 5 or more servings of fruits and vegetables each day.
Whole-grain breads, cereals, rice, pasta, and beans are also
recommended. These guidelines on nutrition may also lower the risk for
some other types of cancer, as well as other health problems.
Tomatoes (raw, cooked, or in tomato products such as sauces or
ketchup), pink grapefruit, and watermelon are rich in lycopenes. These
vitamin-like substances are antioxidants that help prevent damage to
DNA. Some earlier studies suggested lycopenes may help lower prostate
cancer risk, but a more recent study found no link between blood levels
of lycopene and risk of prostate cancer. Research in this area
continues.
There has been hope for some time that taking vitamin or
mineral supplements might affect prostate cancer risk. Some studies
have suggested that taking vitamin E daily might lower risk. But other
studies have found that vitamin E supplements have no impact on cancer
risk, and larger doses may increase risk for some kinds of heart
diseases. Some studies have also suggested that selenium, a mineral,
might lower the risk of prostate cancer.
To study the possible effects of selenium and vitamin E on
prostate cancer risk, doctors conducted the Selenium and Vitamin E
Cancer Prevention Trial (SELECT). In this clinical trial, about 35,000
men were randomized to take one or both of these supplements or to take
an inactive placebo. After an average of about 5 years of daily use,
neither supplement was found to lower prostate cancer risk.
Taking any supplements can have risks and benefits. Before
starting vitamins or other supplements, you should talk with your
doctor.
Several studies are now looking at the possible effects of soy
proteins (called isoflavones) on prostate cancer risk. The results of
these studies are not yet available.
Medicines
Some drugs may also help reduce the risk of prostate cancer.
5 alpha-reductase inhibitors
5 alpha-reductase is the enzyme that changes testosterone into
dihydrotestosterone (DHT). DHT is the hormone which causes the prostate
to grow. 5 alpha-reductase inhibitors are drugs that block that enzyme
and prevent the formation of DHT.
Finasteride (Proscar) is a 5 alpha-reductase inhibitor that is
already used to treat benign prostatic hyperplasia (BPH). It is also
available in a lower dose form (called Propecia) to treat male pattern
baldness.
The Prostate Cancer Prevention Trial (PCPT) was a large
clinical trial designed to see if finasteride could lower the risk of
prostate cancer. Half of the men in the study took finasteride each day
for 7 years, and the other half took a placebo (sugar pill). At the end
of the study, men taking finasteride were less likely to have prostate
cancer than those getting the placebo. At first it looked like the men
taking finasteride had slightly more cancers with high Gleason scores
-- cancers that looked like they were more likely to grow and spread.
It is now thought that this is not true and men who took finasteride
are not more likely to develop high-grade cancer. Researchers are still
watching the men in the study to see if the men taking the drug lived
longer. (More information about the Gleason score can be found in the
section, "How
is prostate cancer diagnosed?")
Finasteride was more likely to cause sexual side effects like
lowered sexual desire and impotence. But it seemed to help with urinary
problems such as trouble urinating and leaking urine (incontinence).
At this time, not all doctors agree whether taking finasteride
to prevent prostate cancer is a good thing. Men thinking about this
should discuss it with their doctors. The results of the PCPT will
become clearer over the next few years.
Dutasteride (Avodart), another 5 alpha-reductase inhibitor, is
currently being tested in a clinical trial to see if it can lower the
risk of prostate cancer. Early results from this study reported this
year indicate that it may have effects similar to that of finasteride.
Other drugs
In a small study, toremifene, an anti-estrogen, decreased the
risk of prostate cancer in men with high grade prostatic
intraepithelial neoplasia. A larger study to confirm this finding is
going on now. Other drugs that may help prevent prostate cancer are now
being tested in clinical trials.
Last Medical Review: 07/30/2009 Last Revised: 07/30/2009
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