What is prostate cancer?

Prostate cancer is a disease in which cells in the prostate gland — a walnut-sized gland in the male reproductive system that resides below the bladder and surrounds the upper part of the urethra (i.e., the tube that carries urine from the bladder) and makes seminal fluid — start to grow out of control.^[1] It is the second most common cancer in men worldwide and is most prevalent in men over the age of 65;^[2] The majority of prostate cancers grow very slowly and are unlikely to cause serious problems. When the cancer is confined to the prostate, long-term prognosis is excellent, but if the cancer begins to grow quickly and spreads to distant organs, it becomes dangerous, and current therapies cannot cure it.