Impact of prior definitive therapy on survival outcomes in men with new hormone sensitive metastatic prostate cancer (mHSPC).

269 Background: In mHSPC, treating the primary tumor may have a biologic effect on the metastatic sites, and definitive therapy in this setting has been hypothesized to delay disease progression and even death. Outcomes with prior definitive therapy in this setting have not been reported. Methods: In this multicenter study, men with new mHSPC, starting androgen deprivation therapy (ADT) were included. Index date was the day of starting ADT. Kaplan-Meier and Cox proportional hazard methods assessed time to castrate resistance (CRPC) and overall survival (OS) in those with or without prior definitive therapy. Variables significant at P < 0.05 were included in the final models. Results: A total of 235 men with mHSPC were included (median age ~ 67 yrs). Prior definitive therapy was performed in 64 men (27%). Results are presented in the table. Conclusions: Definitive treatment was associated with improved time to CRPC and OS in univariate analysis; however, when combined with other prognostic factors the sign...