Prostate cancer causes

Etiology
The specific causes of prostate cancer remain unknown. A man's risk of developing prostate cancer is related to his age, genetics, race, diet, lifestyle, medications, and other factors. The primary risk factor is age. Prostate cancer is uncommon in men less than 45, but becomes more common with advancing age. The average age at the time of diagnosis is 70. However, many men never know they have prostate cancer. Autopsy studies of Chinese, German, Israeli, Jamaican, Swedish, and Ugandan men who died of other causes have found prostate cancer in thirty percent of men in their 50s, and in eighty percent of men in their 70s. In the year 2005 in the United States, there were an estimated 230,000 new cases of prostate cancer and 30,000 deaths due to prostate cancer.

A man's genetic background contributes to his risk of developing prostate cancer. This is suggested by an increased incidence of prostate cancer found in certain racial groups, in identical twins of men with prostate cancer, and in men with certain genes. In the United States, prostate cancer more commonly affects black men than white or Hispanic men, and is also more deadly in black men. Men who have a brother or father with prostate cancer have twice the usual risk of developing prostate cancer. Studies of twins in Scandinavia suggest that forty percent of prostate cancer risk can be explained by inherited factors. However, no single gene is responsible for prostate cancer; many different genes have been implicated. Two genes (BRCA1 and BRCA2) that are important risk factors for ovarian cancer and breast cancer in women have also been implicated in prostate cancer.

Dietary amounts of certain foods, vitamins, and minerals can contribute to prostate cancer risk. Men with higher serum levels of the short-chain ω-6 fatty acid linoleic acid have higher rates of prostate cancer. However, the same series of studies showed that men with elevated levels of long-chain ω-3 (EPA and DHA) had lowered incidence. A long-term study reports that "blood levels of trans fatty acids, in particular trans fats resulting from the hydrogenation of vegetable oils, are associated with an increased prostate cancer risk." Other dietary factors that may increase prostate cancer risk include low intake of vitamin E (Vitamin E is found in green, leafy vegetables), omega-3 fatty acids (found in fatty fishes like salmon), and the mineral selenium. A study in 2007 cast doubt on the effectiveness of lycopene (found in tomatoes) in reducing the risk of prostate cancer. Lower blood levels of vitamin D also may increase the risk of developing prostate cancer. This may be linked to lower exposure to ultraviolet (UV) light, since UV light exposure can increase vitamin D in the body.

There are also some links between prostate cancer and medications, medical procedures, and medical conditions. Daily use of anti-inflammatory medicines such as aspirin, ibuprofen, or naproxen may decrease prostate cancer risk. Use of the cholesterol-lowering drugs known as the statins may also decrease prostate cancer risk. More frequent ejaculation also may decrease a man's risk of prostate cancer. One study showed that men who ejaculated five times a week in their 20s had a decreased rate of prostate cancer, though others have shown no benefit. Infection or inflammation of the prostate (prostatitis) may increase the chance for prostate cancer. In particular, infection with the sexually transmitted infections chlamydia, gonorrhea, or syphilis seems to increase risk. Finally, obesity and elevated blood levels of testosterone may increase the risk for prostate cancer.

Research released in May 2007, found that US war veterans who had been exposed to Agent Orange had a 48% increased risk of prostate cancer recurrence following surgery.

Prostate cancer risk can be decreased by modifying known risk factors for prostate cancer, such as decreasing intake of animal fat.

One research study, by the Cancer Council Victoria, has shown that men who report that they regularly ("more than five times per week") masturbate have up to one third fewer occurrences of prostate cancer. The researchers hypothesize that this could be because regular ejaculation reduces the buildup of carcinogenic deposits such as 3-methylcholanthrene, produced from the breakdown of cholesterol, which could damage the cells lining the prostate. The researchers also speculated that frequent ejaculation may cause the prostate to mature fully, making it less susceptible to carcinogens. It is also possible that there is another factor (such as hormone levels) that is a common cause of both a reduced susceptibility to prostate cancer and a tendency toward frequent masturbation.

There is also some evidence that frequent sexual intercourse is associated with reduced risk of prostate cancer, although contrarily the risks associated with STDs have been shown to increase the risk of prostate cancer. Once the lining of the prostate is affected with cancer, the only known treatments are surgery and radiation therapy. Both may limit the ability to have erections afterward.