Genetics and Cancer - The Genetics of Prostate Cancer
According to the Centers for Disease Control and Prevention (CDC), one in six men will be diagnosed with prostate cancer in their lifetime. The risk is higher in African-American men, among whom one in five will be diagnosed with 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 little to no increased risk of developing prostate cancer.
About 5 percent to 10 percent of prostate cancers are familial, which means there is a father or brother also affected, at typical ages of onset. Familial cancers may be due to a combination of genes and shared lifestyle factors or environmental exposures (multifactorial inheritance). On the other hand, some of these histories can represent a chance occurrence of sporadic cancers. A familial history may also 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. In other words, the more relatives you have with prostate cancer, the higher the risk:
|Number of Relatives With Prostate Cancer
||Prostate Cancer Risk
|1 first-degree relative (father, brother, or son)
||2 to 3 times higher (than the average population risk)
|2 first-degree relatives (father, brother, or son)
||5 times higher (than the average population risk)
|1 first-degree relative and 1 second-degree relative
8 times higher (than the average population risk)
|3 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. 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.
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