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.

The study showed that 49 percent of men treated with Zoladex immediately after radiation therapy were alive 10 years later, compared with 39 percent of men who waited until their tumors got worse before receiving the drug.

In addition to the improvement in survival, only 22 percent of the men who received Zoladex immediately after radiation had their tumors increase in size, compared with 38 percent of the men who delayed drug treatment.

The study was published in the April issue of the International Journal of Radiation Oncology Biology Physics.

“Men diagnosed with prostate cancer can now expect to live longer and live a life free from a recurrence of their disease,” Dr. Colleen Lawton of the Medical College of Wisconsin, a co-author of the study, said in a statement.

Prostate cancer is the most commonly diagnosed cancer in men in the United States with over 230,000 new cases expected this year. It is the second leading cause of death due to cancer, after lung cancer.