Luteinizing Hormone-Releasing Hormone Agonist Therapy and Iodine I 125 Implant in Treating Patients With Previously Untreated Prostate Cancer

RATIONALE: Androgens can cause the growth of prostate cancer cells. Luteinizing hormone-releasing hormone agonists may lessen the amount of androgens made by the body. Internal radiation uses radioactive material placed directly into or near a tumor to kill tumor cells. Giving luteinizing hormone-releasing hormone agonist together with an iodine I 125 implant may be an effective treatment for patients with prostate cancer. PURPOSE: This randomized phase III trial is studying how well giving luteinizing hormone-releasing hormone agonist therapy together with an iodine I 125 implant works with or without additional luteinizing hormone-releasing hormone agonist therapy in treating patients with previously untreated prostate cancer.