Efficacy of androgen deprivation therapy in patients with metastatic castration-resistant prostate cancer receiving docetaxel-based chemotherapy

Purpose: The purpose of this study was to determine the comparative effectiveness of androgen deprivation therapy (ADT) combined with docetaxel (DTX)-based chemotherapy in Korean and Japanese castration-resistant prostate cancer (CRPC) patient cohorts. Materials and Methods: Metastatic CRPC patients who underwent more than three DTX-based chemotherapy cycles in Korea and Japan between 2002 and 2017 were retrospectively analyzed and divided into the DTX-only (DTX, n=30) and combination (DTX+ADT, n=46) groups. Progression-free survival (PFS) was calculated as the time from the start of chemotherapy to the occurrence of either disease progression (prostate-specific antigen [PSA] progression or radiographic progression) or death. The primary end point was PFS and the secondary end point was overall survival (OS). Results: In the DTX and DTX+ADT groups, the median PFS was 6.0 and 11.0 months (log-rank p=0.053). The multivariate Cox regression analysis revealed that the significant predicting factors of PFS were ADT administration (hazard ratio [HR], 0.478; 95% confidence interval [CI], 0.284–0.804; p=0.005) and number of DTX-based chemotherapy cycles (HR, 0.934; 95% CI, 0.899–0.970; p<0.001). In the DTX and DTX+ADT groups, the median OS was 16.0 and 19.5 months (log-rank p=0.825). Through multiple Cox regression analysis, we found that the significant predicting factors of OS were the PSA nadir level (HR, 1.001; 95% CI, 1.000–1.002; p<0.001) and number of DTX-based chemotherapy cycles (HR, 0.932; 95% CI, 0.876–0.991; p=0.024). Conclusions: Concurrent DTX-based chemotherapy and ADT may be beneficial compared with DTX-based chemotherapy alone in chemotherapy-naïve metastatic CRPC patients in terms of the PFS, but not the OS.