Efficacy of Alternative Antiandrogen Therapy for Prostate Cancer That Relapsed after Initial Maximum Androgen Blockade

Purpose: We evaluated the effectiveness of second-line maximum androgen blockade (MAB) with an alternative antiandrogen in patients who relapsed after initial MAB. Materials and Methods: We retrospectively analyzed 47 patients with prostate cancer who relapsed after initial MAB, including surgical or medical castration combined with antiandrogens, from January 1998 to December 2009. When the serum prostate-specific antigen (PSA) level was increased on three consecutive occasions, we discontinued the antiandrogen and then administered an alternative antiandrogen. Seven patients were assessed for antiandrogen withdrawal syndrome (AWS). The effect of the second- line MAB was evaluated by the serum PSA level, and response was subdivided into >= 50% and < 50% PSA reductions from the baseline PSA at the start of second-line MAB. Results: PSA reduction was observed in 32 patients (68.1%). Among them, 23 (48.9%) achieved >= 50% PSA reductions with a mean response duration of 13.4 +/- 5.4 months. Nine (19.2%) patients reached < 50% PSA reductions with a mean response duration of 12.2 +/- 6.2 months. The time to nadir PSA level after first-line MAB in the >= 50% PSA reduction group, < 50% PSA reduction group, and PSA elevation group was 15.6 +/- 12.9 months, 11.8 +/- 6.0 months, and 8 +/- 6.5 months, respectively. That is to say, it was significantly longer in the responder groups (p=0.038). Conclusions: Second-line MAB using an alternative antiandrogen is an effective treatment option before cytotoxic chemotherapy in patients who relapse after initial MAB.