Causes and Risk Factors

No single cause of prostate cancer has been identified. There are likely a variety of causes and contributing factors that lead to prostate cancer. The major known risk factors for prostate cancer are age, race and family history. Although there are no conclusive data, diet and other environmental factors may play a role as well.

Age is the single most important factor in the development of prostate cancer. It is extremely rare for a man under the age of 40 to develop detectable prostate cancer. The chance of having prostate cancer increases rapidly after age 50. In fact, about 80 percent of all prostate cancers are diagnosed in men over the age of 65. A man in his mid-to-late seventies is 130 times more likely to develop prostate cancer than a man in his mid-to-late forties. It is still unclear why prostate cancer rates increase with age; however, the genetic mutations that have been linked to development of cancer occur gradually over time.

Race. A wide variation in incidence has been reported among different races and ethnic groups. African-American men are 65 percent more likely to develop prostate cancer than Caucasian-American men. Moreover, African-American men appear to get more severe forms of prostate cancer and are more than twice as likely to die from it as Caucasian-American men. The reasons for this are unknown. However, diet, genetics and, possibly, inadequate exposure to vitamin D may all play a role.

Asian men living in Asia have the lowest incidence; however, their prostate cancer risk appears to rise the longer they live in Western culture. Prostate cancer is most common in North America and northwestern Europe. It is less common in Asia, Central America and South America. While genetics may play a role, diet is suspected to be a major factor in these racial differences.

Family History. Approximately 25 percent of men with prostate cancer have a history of the disease within their family. However, it is believed that only 9 percent of all prostate cancers are purely hereditary. The picture may be more complex for those patients with a family history since family members typically share other risk factors, including race, diet and other environmental factors. The risk of prostate cancer doubles among men having a father or brother with the disease. With two close relatives, a man's risk increases fivefold, and with three or more close relatives, the risk for developing prostate cancer is alarmingly high—close to 100 percent.

Diet, Obesity and Nutrition. Diet and weight may play a role in the development of prostate cancer. High intake of animal fats, such as those found in red meat, and polyunsaturated fats (corn oil, safflower oil, margarine, etc.) may be associated with higher rates of prostate cancer; however, it is unclear exactly how dietary fat might relate to increased risk.

Vitamin D and Sunlight. Vitamin D is known to protect the body against cancer. While vitamin D is contained in milk and some fish, the main source is from the skin, which forms vitamin D when it is exposed to sunlight. Studies have shown that people living in regions that get less sunlight have higher rates of prostate cancer. This may also help to explain some of the racial differences in the incidence of prostate cancer. People with dark skin absorb less sunlight and are known to have lower levels of vitamin D.

Circulating Male Hormone Level. . Lifetime risk of prostate cancer may be linked to the amount of the male hormone testosterone circulating in a man's body as early as puberty or even in utero, although direct evidence of this link remains to be shown. Prostate cancer cell growth may be fueled by the presence of testosterone. Therefore, one of the most common treatments for prostate cancer, especially if it returns after first-line treatment, is the complete suppression of testosterone production and action in the body. It has also been shown that men who have their testicles surgically removed (orchiectomy; castrated) before puberty rarely develop prostate cancer. However, these observations do not prove that high levels of testosterone in the body cause prostate cancer.