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Glossary
Causes of Prostate Cancer
Prostate cancer is rare in men under 50 years old. However,
the risk increases steadily with age. By the time they are
80, more than half of all men will have some cancerous
growth, though in most cases it goes unnoticed. Prostate
cancer is usually slow-growing and, in men who have it, is
often not the cause of death.
The causes of prostate cancer are largely unknown. It is
clear that the chances of developing prostate cancer increase
in men over 50. Close relatives of men who have had prostate
cancer are also more likely to be affected. Ethnic origin
appears to play a part: men of African heritage seem to be at
highest risk, and men of Far Eastern descent the lowest.
It may be possible to reduce the risk by avoiding a high
fat diet through, for example, cutting down on dairy foods
and red meat.
Genetic Causes of Prostate Cancer
Prostate cancer seems to run in some families, suggesting an
inherited or genetic factor. Having a father or brother with
prostate cancer doubles a man's risk of developing this
disease. The risk is even higher for men with several
affected relatives, particularly if their relatives were
young at the time of diagnosis. Scientists have identified
several inherited genes that seem to increase prostate cancer
risk, but they probably account for only a small fraction of
cases. Genetic testing for these genes is not yet available.
Some inherited genes increase risk for more than one type
of cancer. For example, inherited mutations of the BRCA1 or
BRCA2 genes are the reason that breast and ovarian cancers
are much more common in some families. The presence of these
gene mutations also increases prostate cancer risk. But they
are responsible for a very small percentage of prostate
cancer cases.
Possible Environmental Causes of Prostate Cancer
The most consistent risk factors associated with prostate
cancer are age, family history and African-American
ethnicity. Hormonal factors, as well as high levels of
animal fat and red meat in the diet, are also suspected risk
factors.
Several occupational studies have linked farming to
prostate cancer risk. However, the variety of environmental
exposures in the farming community such as pesticides, engine
exhausts, solvents, dusts, animal viruses, fertilizers,
fuels, and specific microbes, have made it difficult for
researchers in previous studies to sort out which of these
factors is linked to specific diseases.
Exposure to certain agricultural pesticides may be
associated with an increased risk of prostate cancer among
pesticide applicators, according to a large recent study
known as the AHS (Agricultural Health Study) looking at the
causes of cancer and other diseases in the farming community.
The AHS is a collaborative effort involving the National
Cancer Institute (NCI), the National Institute of
Environmental Health Sciences, and the Environmental
Protection Agency.
There is also a weak association between prostate cancer
and cadmium exposure, associated with the occupational
environments of mining and newspaper printing.
Possible Links to Vasectomy
Some studies have raised questions about a possible
relationship between vasectomy (an operation to cut or tie
off the two tubes that carry sperm out of the testicles) and
the risk of developing cancer, particularly prostate and
testicular cancer. Such a relationship, if proven, would be
of importance, as about one in six men over the age of 35 in
the United States has had a vasectomy.
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