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.