Hormone therapy of prostatic bone metastases.

When present at diagnosis or when developing in the course of disease, the presence of bone metastases from prostate cancer is generally considered an indication to begin endocrine therapy, as this is clearly the most effective form of treatment for this problem. Endocrine therapy can stop progression of prostate cancer in 80-85% of cases. Endocrine therapy can relieve pain, prevent pathologic fractures, and prevent neurologic complications from bone metastases from prostate cancer. Rarely, bone scans may become normal after the start of endocrine therapy, but partial improvement or stabilization of bone scans are more commonly seen. While endocrine therapy has been the first line of treatment of metastatic prostate cancer for the past 50 years, the recent development of newer forms of endocrine therapy have increased the options in the past few years. In addition to orchiectomy and estrogens, newer alternatives include inhibitors of androgen synthesis, the class of agents termed "antiandrogens", and luteinizing hormone releasing-hormone (LHRH) analogues either alone or in combination. Orchiectomy causes a prompt fall in serum testosterone and is regarded by many as the "standard" form of endocrine therapy, but there is concern about the psychologic impact of surgery. Estrogens are being used less frequently today because of their real or potential side-effects, including cardiovascular and thromboembolic complications. The development of analogues of LHRH has resulted in another major choice for endocrine therapy, and one which is therapeutically equivalent to orchiectomy or estrogens. Since LHRH analogues may cause an early rise or "flare" in serum testosterone before it drops to castrate level, these agents should not be given alone to patients with severe pain or neurologic problems. The newly available antiandrogen flutamide can block the "flare", and may also improve survival when used with LHRH analogues or orchiectomy, especially when disease is less advanced. Not all studies of "combination therapy" support this conclusion. However, the use of flutamide is increasing significantly in the United States. Both the LHRH analogues and flutamide are fairly safe, but they are very expensive. Their use, in combination, is likely to become a progressively more common form of initial endocrine therapy in the future. The growing application of prostate specific antigen (PSA) as a tumor marker for prostate cancer has made the difficulty in interpreting changes in bone scans a much less critical problem in determining response to endocrine or other forms of therapy for advanced prostate cancer.