Prostate cancer. Illustration of a tumour (white) in the prostate that has spread to the wall of the bladder. The prostate is a small gland found just below the bladder (top) surrounding the urethra (down centre), the tube urine passes through. The causes of prostate cancer are not known, but it is most prevalent in men over 50 years of age. Treatment is with hormone therapy, radiation therapy, chemotherapy or surgery to remove the prostate.