Causes, risk factors and prevention
The genetics of prostate cancer
As many as 17 percent of males in the U.S. will develop prostate cancer in their lifetime.
The majority of cases of prostate cancer are sporadic, which means that one person in the family developed prostate cancer by chance at a typical age of onset. In these cases, other male relatives have a moderately increased risk of developing prostate cancer.
About 15 percent of prostate cancers are familial, which means there is a father or brother also affected at typical age of onset. Familial cancers may be due to a combination of genes and shared lifestyle factors or environmental exposures (multi-factorial inheritance). On the other hand, some of these histories can represent a chance occurrence of sporadic cancers. A familial history also may arise due to a single gene mutation (hereditary cancer) that has reduced penetrance (a mutation associated with lower cancer risks and later onset of cancer). In general, with familial cancer, close relatives have a modestly increased risk of developing the cancer in question. The chance that genetic testing will be beneficial in further assessing cancer risks is usually small. Studies have found a trend of an increased chance to develop prostate cancer, with an increasing number of family members affected. In other words, the more relatives you have with prostate cancer, the higher the risk:
Number of relatives with prostate cancer
The higher your risk
|one first-degree relative (father, brother or son)||two to three times higher (than the average population risk)|
|two first-degree relatives (father, brother or son)||five times higher (than the average population risk)|
|one first-degree relative and one second-degree relative||eight times higher (than the average population risk)|
|three first-degree relatives (father, brother or son)||11 times higher (than the average population risk)|
Approximately 5 percent to 10 percent of all prostate cancers and 45 percent of cases in men younger than age 55 can be attributed to a cancer susceptibility gene that is inherited as a dominant trait (from parent to child). Genetic heterogeneity has been observed with prostate cancer, which means that more than one gene has been implicated in its cause, including genes on chromosomes 1, 7, 8, 10, 11, 17 and X. At present, there are many continuing research studies to determine the specific mechanism of how gene mutations contribute to an increased susceptibility for prostate cancer; clinical testing is not available at the time of this writing.