The greatest risk factor for prostate cancer is age. This risk increases significantly after the age of 50 in white men who have no family history of the disease and after the age of 40 in black men and men who have a close relative with prostate cancer. About two-thirds of all prostate cancers are diagnosed in men age 65 and older. The older the patient, especially if they are over 70, the less aggressive the disease usually behaves.