Efficacy of peripheral androgen blockade on prostate cancer: Results of CALGB 9782

Abstract

4559 Background: The treatment of patients with elevated PSA after definitive local therapy continues to be elusive. Many patients are reluctant to undergo androgen suppression therapy due to long-term effects. Enthusiasm has been seen for peripheral androgen blockade for such patients. Methods: We enrolled 101 patients with a climbing PSA after definitive local therapy in a mult-institutional trial. All patients had undergone previous definitive therapy defined as either a radical prostatectomy or radiation therapy. All patients had a rising PSA, above 1 ng/ml, with no detectable evidence of recurrent disease. CT and bone scans were negative. Patients received a combination of oral therapy consisting of Finasteride, at a dose of 5 mg/day, and Flutamide, at a dose of 250 mg TID. Results: The median age was 71, with a median baseline testosterone level of 322 ng/dl. A >80% PSA decline was seen in 91/94(97%) of the patients. The other three patients had drops of 77%, 73% and 38%, all of which were maintained for at least 28 days. The median time to nadir of PSA was 3.2 months. Currently, 64 patients remain on therapy with a median follow up of 33 months. Only 21 patients have progressed through this therapy, and some of these have responded to additional hormonal maneuvers, such as Flutamide withdrawal and gonadal androgen deprivation. The toxicity is very mild, with almost no reported grade 3/4 toxicity, and most grade 2 toxicity reported at <5% level. Conclusions: The combination of Finasteride and Flutamide is highly effective in suppressing PSA levels in patients with serologic progression after local therapy. Median response duration has not been reached at nearly 3 years. Its apparent efficacy and favorable toxicity profile suggest that further investigation in randomized trials may be warranted. No significant financial relationships to disclose.