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 12 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.