Prostate cancer patients treated with the hormonal drug Zoladex immediately after radiation therapy live longer than men who are not prescribed the drug right away, researchers said on Friday.Zoladex, sold by AstraZeneca Plc, reduces levels of sex hormones -- testosterone in men and estrogen in women -- and is also used to treat hormone-dependent breast cancer in premenopausal women.Side effects of the drug include potential bone loss and loss of libido, said Dr. Howard Sandler, chairman of the American College of Radiology’s genito-urinary cancer committee.A 10-year study, involving 977 patients with locally advanced prostate cancer, was carried out by the clinical research arm of the radiology group.