Trans-Pacific variation in outcomes for men treated with primary androgen-deprivation therapy (ADT) for prostate cancer

Objectives To compare directly survival outcomes of primary androgen-deprivation therapy (PADT) in Japan, where this treatment is endorsed by guidelines, with outcomes in the USA, where it is not. Patients and Methods Data were compared between men receiving PADT in the USA Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry and the Japanese Cancer of the Prostate (J-CaP) registry database. Competing risks regression was used to assess prostate cancer-specific mortality (CSM), adjusting for age, Japan Cancer of the Prostate Risk Assessment (J-CAPRA) score, diagnosis year, and treatment type [combined androgen blockade (CAB) vs castration monotherapy], comorbidity, and practice type. Results Men on PADT in J-CaP (13 880 men) were older than those in CaPSURE (1633 men), and had higher-risk disease (mean J-CAPRA score 3.8 vs 2.1, P < 0.001). They more often received CAB: 66.9% vs 46.4% (P < 0.001). Despite different risk profiles between the cohorts, CSM was similar on univariate analysis (log-rank P = 0.88). On multivariable regression, the subhazard ratio for CSM was 0.52 for J-CaP vs CaPSURE (95% confidence interval 0.40-0.68). Conclusions Men on PADT in Japan have less than half the adjusted CSM than those in the USA. These findings support both existing guidelines endorsing PADT in Asia and discouraging its use in the West. Elucidating the reasons behind these substantial differences, which probably include both genetic and dietary/environmental factors, may help explain the varying epidemiology of prostate cancer on either side of the Pacific.