92 Background: Primary androgen deprivation therapy (PADT) is endorsed as an option for monotherapy for localized prostate cancer by guidelines in Asia but not in the United States (US) or Europe. PADT use is common, however, in both the US and Japan. Prior studies on either side of the Pacific have reported disparate outcomes for PADT; we aimed to explore these differences in a direct comparison study. Methods: Data were drawn from the US community-based CaPSURE registry and from J-CaP, comprising men in Japan treated with PADT. 1934 men treated with PADT were included from CaPSURE, and 16,300 treated in J-CaP. Risk adjustment was based on the validated Japan Cancer of the Prostate Risk Assessment (J-CAPRA) score. Cox proportional hazards regression was used to assess prostate cancer-specific mortality (CSM), adjusting for age, J-CAPRA, year of diagnosis, and treatment type (combined androgen blockade [CAB] vs. castration (medical or surgical) monotherapy). Results: Men treated with PADT in J-CaP were older than those in CaPSURE (mean age 75.0 vs. 72.7, p<0.001), and had higher risk disease (mean J-CAPRA score 3.0 vs. 2.1, p<0.001). They were more likely to be treated with CAB: 67.1% vs. 44.5% (p<0.001). In the Cox model, the hazard ratio (HR) for PCSM was 0.31 for J-CaP compared to CaPSURE, 95% CI 0.25–0.40. In J-CaP, CAB improved survival compared to castration alone (HR 0.81, 95% CI 0.66–1.0), but this effect was not observed in CaPSURE (HR 0.96, 95% CI 0.69–1.34). For all-cause mortality, the HR for J-CaP was 0.27 (95% CI 0.24–0.30). Conclusions: Adjusting for multiple factors including disease risk and type of androgen ablation, men treated with PADT in Japan compared to the US have more than 3-fold lower CSM and 4-fold better overall survival. CAB improved outcomes compared to castration alone in J-CaP but not in CaPSURE. These findings support existing guidelines both encouraging PADT in Asia and discouraging its use in the West. The reasons for these substantial differences likely include both genetic and dietary/environmental factors, as well as potential confounding variables such as comorbidities. Such factors may explain varying biology of prostate cancer on both sides of the Pacific.
Primary Androgen Deprivation Therapy for Nonmetastatic Prostate Cancer in Asia: Unique or Not?
