Efficacy of buserelin in advanced prostate cancer and comparison with historical controls.

Buserelin (B) is a synthetic nonapeptide analogue of native LHRH. Upon continued administration it reliably lowers the serum testosterone level to less than 100 ng/dl. It has been used in a clinical trial for the treatment of patients with stage C, D1, and D2 prostate cancer. Analysis of efficacy of testosterone suppression and toxicity included all 207 buserelin-treated patients. A comparison with historical controls from two National Prostate Cancer Project (NPCP) studies considered only the 147 evaluable patients with distant metastases (stage D2). All patients received buserelin, 500 micrograms q 8 hours subcutaneously (s.c.) for the first 7 days and then elected to take 200 micrograms s.c. daily or 400 micrograms q 8 hours by the intranasal (i.n.) route. Seventy-three percent elected s.c. administration. Only 2% changed the route of administration. The serum testosterone (T) level increased during week 1 in both the s.c. (426 ng/dl) and the i.n. (521 ng/dl) group but reached castrate (less than 100 mg/dl) levels by 4 weeks in 90% of patients. Subsequently, the likelihood of having a T level greater than 100 was higher for those treated by the i.n. than the s.c. route. The mean T level 4 and 12 months after therapy for the s.c. treated patients was 29 and 28. These values were 61 and 53 for those taking i.n. buserelin. This difference may in part be due to poor compliance. Toxicity was minor. Twelve percent of 151 s.c. treated patients had at least one episode of reaction at the injection site. None required discontinuation of the agent. Seventy-two percent experienced hot flushes; this was the same for both the s.c. and i.n. groups. Only 2 of 207 patients had a severe exacerbation of symptoms (spinal cord compression) during the first week of therapy. The criteria for response to therapy were those of the NPCP. There was no significant difference in the percentage of patients achieving a response when comparing the B-treated D2 patients to the NPCP D2 patients treated with DES, 3 mg daily, or orchiectomy. More of the B-treated patients entered with pain, a poor performance status, and weight loss than the DES/orchiectomy group. Nonetheless, the progression-free survival did not differ among the treatments. In summary, buserelin reliably lowers the serum T level by week 4 in 95% of men. Treatment efficacy is equivalent to a historical group treated with either DES or orchiectomy.