WHO IS AT RISK FOR DEVELOPING PROSTATE CANCER?
Any normal man can develop prostate cancer because normal men have
male hormones. The prostate does not develop properly without testosterone,
the most common male hormone, so men with severe male hormone deficiencies
(or those who have been castrated before puberty) are not at risk.
There are four main risk factors: age, race, family history, and diet.
Age
The older you are the greater your risk of developing prostate cancer.
Although the disease is rare in men under 45 years of age, the incidence
of prostate cancer increases faster with age than the incidence of any
other major cancer. The chart shows that only 2.4% of the Canadian men
who were diagnosed with prostate cancer in 2001 were between 40 and
54 years of age. This is not to say that men in their forties and early
fifties do not get prostate cancer; we only want to emphasize that the
risk of developing prostate cancer increases with age.
Race and Nationality
Research and statistics suggest that geographical, cultural, and racial
factors affect men’s prostate cancer risk. Canadian men of African
or Caribbean ancestry have the highest risk. Prostate Cancer Canada puts it bluntly: “African-American men are
65% more likely to develop prostate cancer than Caucasian-American men,
and the risk of an African-American man dying of prostate cancer is
about 100 times that of a Chinese man living in China.” The chart
shows the racial groups at lowest to highest risk (from left to right).
Note: These racial categories
are based on those most frequently used by cancer registry databases
in the United States. These databases usually categorize South Asian
people (defined as those from India, Pakistan, Bangladesh, and Sri Lanka)
as part of the “Asians and Pacific Islanders” group. However,
studies suggest that South Asian men are at a higher risk for prostate
cancer than others within the “Asians and Pacific Islanders”
category. As you can tell, racial and ethnic categories are difficult
to determine and to describe accurately and sensitively; CPCN has made
every effort to be clear and respectful when discussing these issues.
Scientists are not sure why race appears to affect prostate cancer
risk. There are subtle genetic and hormonal differences among the races
that may predispose certain groups to prostate cancer. For example,
levels of testosterone tend to vary.
Cultural and geographic factors also probably come into play. Diet,
in particular, may play a role in the development of prostate risk.
We think this because of studies looking at the prostate cancer risk
of men from various racial and national backgrounds who have moved to
North America. As these men start to adapt by eating different foods
from those usually consumed in their countries of origin, their prostate
cancer risk changes. For example, Asian men who remain in China or Japan
are at lower risk than Chinese or Japanese men who have moved to North
America.
Where you live also affects your prostate cancer risk because of environmental
factors such as exposure to chemical carcinogens (e.g., insecticides),
lead, or sunlight. Perhaps because of the benefits of vitamin D, prostate
cancer risk is less for those who live close to the equator and get
more hours of sunlight in a day. Human skin can produce vitamin D when
it is exposed to the UVB (Ultraviolet medium waves) in sunlight, but
UVB only reaches ground level when the sun is high in the sky. Those
furthest from the equator, then, can go for months without the opportunity
to produce vitamin D from sunlight. Perhaps this lack of exposure to
sunlight is part of the reason that, in national comparisons, the highest
incidence of prostate cancer is in Scandinavian countries. Another interesting
fact is that dark skin absorbs less sunlight than light skin, which
may contribute to the higher incidence of prostate cancer among men
of African or Caribbean ancestry.
Family History
If one of your first-degree relatives (your father or brother) has had
prostate cancer you are approximately 2 to 2 1/2 times more likely than
the average man to be diagnosed with the disease during your lifetime.
Having two first-degree relatives with prostate cancer increases your
risk to about 5 to 10 times that of a man with no family history, and
your risk soars to almost 100% if three or more first-degree relatives
have had prostate cancer. If you find yourself in this last category,
remember the phrase “in your lifetime” and remember that
statistics are not destiny. Nevertheless, if a close relative has been
diagnosed with prostate cancer, tell your doctor, get regular checkups,
and take preventative measures. If more distant relatives have had prostate
cancer, uncles and cousins, for example, you should still be extra careful.
However, the closer the relative with prostate cancer (and the more
close relatives who have been diagnosed), the greater your risk.
Estimates are that approximately 10 per cent of all the prostate cancer
cases are hereditary, in other words, that they are a consequence of
an inherited genetic predisposition. Research is preliminary, but the
genes HPC1, HPC2, HPCX, and CAPB seem to be responsible for an increased
likelihood of developing prostate cancer, although other genes are involved
too. To date, no genetic tests are available for routine screening because
this research is so new.
The risk of prostate cancer also appears to increase in men with BRCA1
and BRCA2 gene mutations; these are commonly associated with hereditary
breast and ovarian cancer. Men with BRCA1 mutations have a slightly
increased risk. Men with BRCA2 mutations have an estimated lifetime
risk of almost 20 per cent. There is a simple blood test to see whether
you have BRCA1 or BRCA2 mutations, so, if your mother or sisters have
had breast or ovarian cancer, you may wish to have this test.
Alert: Men with a family
history of prostate cancer or with BRCA1 or BRCA2 mutations should begin
annual prostate cancer screening by age 40. Experts estimate that 65
per cent of the men who are diagnosed with prostate cancer before the
age of 56 have hereditary prostate cancer.
Diet
Research suggests that diets high in saturated fat and low in fibre
and in fruits and vegetables are associated with higher prostate cancer
risk. Also, phytoestrogens, selenium, lycopene, garlic, vitamin C, and
vitamin D seem to play a role in reducing prostate cancer risk. (See
the information on the role of diet in prostate cancer prevention.)
Other Risk Factors
A few other life choices or circumstances may also increase your risk
of developing prostate cancer, although researchers are more tentative
in their conclusions here.
Being overweight or obese may contribute to a man’s risk. Also,
those who are overweight or obese and develop prostate cancer have a
greater risk of dying from the disease than those with a normal height
to weight ratio. This risk may relate to diet and to the fact that high
body fat usually means increased levels of testosterone, the hormone
that helps to fuel prostate cancer growth.
Use of anabolic steroids, which were created to treat testosterone
deficiencies, may also increase a man’s risk of developing prostate
cancer.
Myths
No link has been established between the age at which a man reaches
puberty and prostate cancer risk.
Neither sexual behaviour (e.g., the frequency of orgasm or the type
of sexual activity) nor sexual orientation (e.g., heterosexual, homosexual,
or bisexual) affects prostate cancer risk.
Activities that put pressure on the prostate, such as long distance
cycling, riding horses, or extensive driving, have not been found to
increase prostate cancer risk.
Peter E. Levers, Prostate cancer: A clinical overview,
CPCN
Review of Peter Hyde’s Sunlight, Vitamin D, and Prostate Cancer
Risk, CPCN
