Clinical efficacy of alternative antiandrogen therapy in Japanese men with relapsed prostate cancer after first-line hormonal therapy

Background: To confirm the effectiveness of alternative antiandrogen therapy (AAT) in Japanese patients with prostate cancer relapse after first‐line hormonal therapy. Methods: A total of 80 patients who had successive serum prostate‐specific antigen (PSA) progression after first‐line hormonal therapy (luteinizing hormone‐releasing hormone agonist alone: 21 cases; combined antiandrogen blockade therapy: 59 cases) were enrolled. We evaluated the positive ratio of antiandrogen withdrawal syndrome (AWS), the PSA responses with second‐ and third‐line AAT, and cause‐specific survival in terms of the effectiveness of AAT. Results: The overall positive AWS ratio after first‐line therapy was 33%, while that after second‐line therapy was 7%. There was no correlation between the first‐line PSA response and the positive AWS. Of the 10 positive and the 20 negative AWS cases, secondary antiandrogen administration was effective in 50% and 60% of cases, respectively. The positive PSA responders at second‐ and third‐line therapy were 51% and 13%, respectively. For second‐line therapy, the effective rates from steroidal to non‐steroidal, from non‐steroidal to non‐steroidal antiandrogen, and from non‐steroidal to steroidal were 83%, 43%, and 14%, respectively. The cause‐specific survival of the second‐line responders was significantly better than that of the non‐responders. Conclusion: There was a substantial number of patients who found second‐line AAT to be modestly effective. Flutamide was effective as an alternative antiandrogen for the patients' relapse treatment with bicalutamide in Japanese men.