Background: The standard of care for patients with unresectable stage III non-small cell lung cancer (NSCLC) is concurrent chemoradiotherapy followed by durvalumab maintenance based on outcomes from the PACIFIC trial. However, PACIFIC did not include Veterans, a unique population with significant co-morbidities; thus, the impact of durvalumab on survival of Veterans with stage III NSCLC is unknown. Methods: Using the U.S. Department of Veterans Affairs Corporate Data Warehouse, patients with stage III non-small cell lung cancer who received chemoradiotherapy and at least one dose of durvalumab were selected. Kaplan-Meier survival analysis and univariate Cox proportional hazards modeling were used to determine progression-free survival (PFS), overall survival (OS) and independent predictors of PFS and OS. PFS was manually extracted by review of serial surveillance scans. All statistical computations were performed using SAS 9.4 software. Results: 1106 Veterans met our inclusion criteria. The median age was 69. 95.1% (n = 1052) were male. The median Charlson Comorbidity Index was 1. 86.4% (n = 956) reported current or former tobacco use. 48.1% (n = 532) had adenocarcinoma histology, 48.4% (n = 535) squamous cell, 0.5% (n = 5) large cell, 0.3% (n = 3) neuroendocrine, and 0.1% (n = 1) sarcomatoid. 60% (n = 619) had AJCC 8^th edition stage IIIA disease, 34.5% (n = 382) stage IIIB, and 3.3% (n = 36) stage IIIC. Median PFS was 19.9 months (95% CI: 16.9 – 23.6) and median OS was 34.9 months (95% CI: 29.7 – not reached). In univariate survival analyses, adenocarcinoma histology (HR 1.14, p = 0.03) predicted progression. Older age (HR 1.03, p< 0.0001) and stage IIIB/IIIC disease (HR 1.05, p = 0.008) predicted inferior OS. 18.4% (n = 204) of patients completed all planned cycles of adjuvant durvalumab. The median number of durvalumab infusions received was 6 (range: 1 – 38). Among evaluable patients, 175 (19.4%) discontinued durvalumab for progression, 211 (23.4%) discontinued for suspected immune-related toxicity and 17 (1.9%) died during treatment. Conclusions: While several factors have led to the improvement of OS in patients with stage III NSCLC over time, we report a doubling of median OS in Veterans with stage III NSCLC who received chemoradiotherapy plus durvalumab as compared to historical cohorts who received chemoradiotherapy alone (1). Veterans in our study received a lower median number of durvalumab infusions as compared to patients in the PACIFIC trial (6 vs. 14), and a significant proportion discontinued durvalumab due to suspected immune-mediated toxicity (23.4%). If further analyses confirm our findings, investigation of alternative dosing regimens and/or dosing intervals of durvalumab in order to balance safety and efficacy of durvalumab therapy in Veterans is warranted. (1) Santana-Davila R et al. J Clin Oncol. 2015 Feb 20;33(6):567-74.