National population-based survival estimates after definitive radiation therapy for prostate cancer.

395 Background: Understanding contemporary radiation therapy outcomes for prostate cancer (i.e., metastasis, death) is important for shared decision-making and setting expectations for patients and providers. Unfortunately, long-term outcome estimates are often derived from meta-analyses of outdated prospective clinical trials or population-based data lacking reliable clinical details (e.g., incident metastatic disease). For these reasons, we used a recently validated, natural language processing algorithm to identify incident metastatic prostate cancer within the electronic medical records of men treated with radiation therapy for localized prostate cancer in order to conduct an innovative and contemporary population-based survival outcomes study. Methods: We used national administrative, cancer registry, and electronic health record data for patients undergoing definitive radiation therapy with or without concurrent androgen deprivation therapy (ADT) within the Veterans Health Administration from 2005 to 2015. We used National Death Index data through 2019 for overall and prostate cancer-specific survival, and identified the date of incident metastatic prostate cancer using a validated natural language processing algorithm. We estimated metastasis-free, prostate cancer-specific, and overall survival using Kaplan-Meier methods. Results: We identified 41,876 patients treated with definitive radiation therapy for prostate cancer from 2005 through 2015, and followed them for over 8 years (follow up, median, 8.7 years, age at diagnosis, median, 65 years). Most patients had intermediate (42%) and high risk (33%) disease, with nearly half treated with ADT as part of initial therapy (44%). Unadjusted 10-year metastasis-free survival was 96%, 92%, and 80% for low, intermediate, and high risk disease. Similarly, unadjusted 10-year prostate cancer-specific survival was 98%, 97%, and 90% for low, intermediate, and high risk disease. Unadjusted overall survival was lower across disease risk categories at 77%, 71%, and 62% for low, intermediate, and high risk disease. Conclusions: These data provide population-based benchmarks for clinically relevant endpoints, including metastasis-free survival, among patients with low, intermediate, and high risk prostate cancer undergoing radiation therapy using contemporary techniques. The survival rates for high risk disease, in particular, compare favorably with historical outcomes.