The causes of prostate cancer are poorly understood and there are no proven prevention measures although researchers continue to examine possible risk factors and preventive approaches.
Increasing age is by far the most important risk factor for prostate cancer, with more than 81% of cases diagnosed in 2010 occurring in men 60 years of age or older. Younger men diagnosed with prostate cancer are more likely to die prematurely from the disease than older men, as there is, on average, more of their lifetime left in which the cancer can progress.
Family history of prostate cancer is also a risk factor for the disease. Between five and 10% of prostate cancers may be due to an inherited genetic predisposition. Men with first-degree relatives diagnosed with prostate cancer are two to three times more likely to develop prostate cancer as men with no affected relatives, and the risk may be higher if a first-degree relative was diagnosed before the age of 60 years.
The genetic basis for familial prostate cancer is not fully understood. Men carrying mutations of the breast cancer susceptibility genes BRCA1 or BRCA2 have an increased risk of several types of cancer, including prostate cancer. Male carriers of BRCA2 mutations have a 3.5-fold increased risk of prostate cancer and an earlier age of onset and have been reported to have poorer survival rates than those without BRCA2 mutations.
A mutation of the gene HOXB13 has also been shown in recent research to substantially increase prostate cancer risk.
Sexually transmitted infection
The possibility that sexually transmitted infection (STIs) might increase the risk of prostate cancer has been extensively studied, without producing conclusive evidence that any specific STIs increase prostate cancer risk.
Evidence on the links between prostate cancer risk and modifiable lifestyle factors is limited. A comprehensive review of the impact of diet and physical activity on cancer by the World Cancer Research Fund concluded that foods containing lycopene (such as tomato) or selenium probably protect against prostate cancer, while diets high in calcium probably increase the risk. However, a more recent review by the World Cancer Research Fund in 2014 concluded that links between prostate cancer risk and foods containing lycopene and selenium supplements have been downgraded from strong evidence of a decreased risk, to no conclusion possible. Additionally, the link between diets high in calcium and prostate cancer has been downgraded from strong evidence of an increased risk of prostate cancer, to limited evidence.
A randomised controlled trial, however, found no evidence that supplementary selenium reduced prostate cancer risk.
The World Cancer Research Fund review also concluded that there was limited suggestive evidence that processed meat and milk and dairy products increase the risk of prostate cancer, while fish and pulses, including soy foods, may decrease the risk.
Physical activity may be associated with a small reduction in prostate cancer risk, while being sedentary for long periods, irrespective of the overall amount of physical activity undertaken, is associated with an increased risk.
More research is required before any firm conclusions can be drawn regarding the link between lifestyle factors and prostate cancer risk.
Chemoprevention, or the use of natural or synthetic agents to reduce the incidence of cancer in those at increased risk, is being investigated but is not in routine use for prostate cancer.
The anti-androgen drug finasteride is thought to prevent prostate cancer, but this apparent benefit was limited to less aggressive cancers and it appeared that risk of more aggressive cancers was increased by the drug. The United States Food and Drug Administration accepted the December 2010 advice of its Oncologic Drugs Advisory Committee that finasteride and the closely related drug dutasteride “do not have a favourable risk-benefit profile for the proposed use of chemoprevention of prostate cancer in healthy men”.
A trial examining selenium and vitamin E supplementation in healthy men (The SELECT trial) found that these agents did not prevent prostate cancer and that supplementation with vitamin E was associated with a significantly increased risk of prostate cancer of 17%.
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