Antiandrogen withdrawal syndrome with cyproterone acetate.

OBJECTIVES: To determine whether the antiandrogen withdrawal syndrome occurs with the steroidal antiandrogen cyproterone acetate. METHODS: Cyproterone acetate was withheld in 12 patients with progressing androgen-independent metastatic prostate cancer. Eight patients had been receiving cyproterone acetate concomitant with androgen ablation, and in 4 patients it was prescribed after failure of androgen suppression. Time to response and to disease progression were defined by serum prostate-specific antigen (PSA) levels and imaging studies. RESULTS: PSA levels decreased in 5 of the 1 2 patients; in 4 of them (33%), the decrease exceeded 50%. The decline lasted a median of 24 weeks (range 9 to 37.8). All 5 patients had received initial concomitant exposure to androgen ablation and cyproterone acetate. CONCLUSIONS: We recommend that the steroidal antiandrogen cyproterone acetate be added to the list of agents capable of inducing antiandrogen withdrawal syndrome.