The cause of prostate cancer is unknown, although some studies have shown a relationship between high dietary fat intake and increased testosterone levels. When testosterone levels are lowered either by surgical removal of the testicles (castration, orchiectomy) or by medication, prostate cancer can regress. There is no known association with benign prostatic hyperplasia (BPH).

Prostate cancer is the third most common cause of death from cancer in men of all ages and is the most common cause of death from cancer in men over 75 years old. Prostate cancer is rarely found in men younger than 40.

Men at higher risk include black men older than 60, farmers, tire workers, painters, and men exposed to cadmium. The lowest incidence occurs in Japanese men and vegetarians.

Prostate cancers are classified or staged based on their aggressiveness and how different they are from the surrounding prostate tissue. There are several different ways to stage tumors; one of the more common is the A-B-C-D staging system (also known as the Whitmore-Jewett system).

• A: tumor not palpable (unable to be felt on physical examination). Usually detected by accident after prostate surgery done for other reasons.
• B: tumor is confined to the prostate and usually detected by physical examination or PSA testing.
• C: extension of tumor beyond the prostate capsule without spread to lymph nodes.
• D: cancer has spread (metastasized) to regional lymph nodes or other parts of the body (bone and lungs for example).

This system also contains several substages.