Cancer, prostatic: Cancer of the gland (prostate) that produces some of the components of semen fluid. The second leading cause of death of males in the U.S. Prostate cancer is often first detected as a hard nodule during a routine rectal examination. The PSA blood test is a screening test for prostate cancer. Diagnosis of prostate cancer is established when cancer cells are identified in prostate tissue obtained by a biopsy. In some patients, prostate cancer is life threatening. In many others, prostate cancer can exist for years without causing any health problems. Treatment options for prostate cancer include observation, radiation therapy, surgery, hormonal therapy, and chemotherapy.