Survival In Men Diagnosed With Castration Resistant Prostate Cancer: A Population-Based Observational Study In Sweden.

e16555 Background: Data focusing on the castration resistant phase of prostate cancer (PC) outside clinical trial settings are scarce. This study aims to investigate PC-specific and overall survival (OS) in men with castration resistant prostate cancer (CRPC) on a population level. Methods: The STHLM-0 cohort (n = 400 000) with data on all prostate specific antigen (PSA) values and prostate biopsies taken in Stockholm, Sweden, from 2003 to 2015 were linked to other population registries. All men with a PC diagnosis and rising PSA after three months consecutive use of gonadotropin-releasing hormone or surgical castration were defined as CRPC (n = 1712). Kaplan-Meier was used to estimate median time-to-event and 95% confidence intervals (CI). Patients were stratified by metastasis status at PC diagnosis and multivariable Cox regression was used to adjust for clinical subgroups, including Gleason, age, T stage and calendar period (2006-2011 vs 2012-2015). Results: Metastasis at PC diagnosis was associated with shorter OS from castration resistance. From CRPC onset the median OS was 22.8 months (95% CI 21.2-25.5) and 13.1 (95% CI 11.5-14.2) months for patients without and with metastasis at PC diagnosis, respectively. The median PC-specific survival from CRPC was 30.7 (95% CI 27.9-34.7) months and 13.5 (95% CI 12.3-16.1) months for patients without and with metastasis at PC diagnosis, respectively. For patients with metastasis at PC diagnosis, factors influencing OS from CRPC were; entering CRPC stage in the later vs earlier calendar period (HR 0.61 95% CI 0.48-0.78, p < 0.001), age > 80 vs < 70 (HR 1.46, 95% CI 1.05-2.02, p < 0.02), T4 vs T1 stage (HR 1.56, 95% CI:1.02-2.37, p < 004). For patients without metastasis at PC diagnosis, developing CRPC in the later vs the earlier calendar period was associated with superior survival from CRPC (HR 0.78 95% CI 0.65-0.92, p < 0.004). Conclusions: Metastasis at PC diagnosis was associated with worse survival outcomes in CRPC patients. Individuals who became castration resistant in the later calendar period survived longer compared to those in the same stage in the earlier calendar period, most likely due to the introduction of novel agents for CRPC patients and more accurate staging methods.