Extended analyses: Combined androgen blockade (CAB) therapy with bicalutamide vs. luteinizing hormone-releasing hormone agonist (LHRHa) monotherapy in Japanese men with untreated advanced prostate cancer

Abstract

5063 Background: Phase III trial (PIII) results of first-line CAB (bicalutamide 80 mg [licensed dose in Japan] plus LHRHa) for Japanese men with advanced prostate cancer (PC) were shown to be significantly better than LHRHa monotherapy in TTP and TTTF without reduced tolerability, and achieve earlier QOL improvement. This report was cited in the 2007 Update of ASCO Practice Guideline Recommendations. PSA was also decreased significantly faster and lower with CAB than LHRHa alone. The PIII showed no difference in overall survival (OS) between the groups because of lack of events, but a long-term follow-up of PIII conducted by CABPC Study did indicate a significant OS benefit for CAB over LHRHa alone. Here we present the final analyses of this long-term follow-up study. Methods: Five-year survival rates for 203 Japanese men with advanced PC in the original study (CAB=102, LHRHa alone=101) were calculated (Kaplan- Meier method), and OS, cause-specific survival (CSS) and OS by PSA nadir were analyzed by use of Cox regression (HR) and log-rank test. Results: Both groups were demographically similar. At the 270 weeks median follow-up, there were 26 deaths in the CAB and 38 in the LHRHa alone. OS for the CAB group was significantly better than for LHRHa alone p=0.0425. Five-year survival rates for CAB and LHRHa alone were 75.3% and 63.4% respectively. CSS was higher with CAB, but the difference was not statistically significant. OS by PSA nadir ≤1 ng/mL was significantly better than for those >1 ng/mL (p<0.0001). Conclusions: For Japanese men with advanced PC, long-term follow-up data had shown a significant OS benefit for CAB with bicalutamide compared with LHRHa monotherapy; and exploratory data suggesting that lowering PSA may be prognostic for OS. In this study, antiandrogens were added to most men with disease progression in the LHRHa alone (response rate 78%, median duration of response 40wks); most with progression in the CAB were observed for AWS (AWS rate 39%, median duration of AWS 58wks). So this result suggests that immediate CAB prolongs survival better than deferred CAB. No significant financial relationships to disclose.