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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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