The major risk factors associated with prostate cancer include older age, ethnicity, family history, and high levels of the hormone dihydrotestosterone (DHT) — a converted form of testosterone. On average, African Americans have 10 percent higher testosterone levels than Caucasians, and also have the highest rate of prostate cancer. Japanese people, who have lower testosterone levels, have the lowest prostate cancer rate.

But genetics plays a major role in only a very small number of prostate cancer cases, with mutations in the androgen (sex hormone) receptor genes being the most common cause within this group. As with breast cancer, we also see mutated BRCA1 and BRCA2 genes in a rare number of prostate cancer patients.

In most cases, the genes are not actually mutated, but rather overactive. For example, overactivity of the enzyme that transforms testosterone into the much more powerful dihydrotestosterone (5-alpha-reductase enzyme) significantly increases the risk of developing prostate cancer. Men with a deficiency in this enzyme never develop prostate cancer.

In fact, the relatively low activity of this enzyme in men of Asian ethnicity may account for the low rate of prostate cancer among Asians.

Other important risk factors for prostate cancer include:

• Having a vasectomy

• Early first-time intercourse

• Large number of sex partners

• History of one or more sexually transmitted diseases

• Unprotected anal sex