Background: The PACIFIC study (PS) concluded that the use of durvalumab from 1 to 42 days after concurrent chemoradiotherapy (CXRT) in stage 3 unresectable non-small cell lung cancer (NSCLC) increased the median overall survival (mOS) from 29 to 48 months. It also showed a benefit in tumors with PD-L1 <25%. However, a post-hoc analysis of the PS showed no survival benefit with durvalumab in patients with PD-L1 <1% but was not statistically powered. Currently in the US, durvalumab is approved irrespective of PDL-1 percentage, whereas in Europe it is not approved for tumors with PDL-1 <1%. Also, there was no survival benefit in starting durvalumab within and after 2 weeks of CXRT. Our objectives in this study are to analyze the impact of PDL-1 expression and the date of initiation of durvalumab post CXRT on mOS. Methods: We conducted a retrospective observational study of stage 3 unresectable NSCLC patients who received durvalumab post CXRT at LSU Health Shreveport from 2018 to 2021. A survival analysis was done including the following variables: age, race, sex, tumor histology, tumor PD-L1 percentage, and date of initiation of durvalumab post CXRT. P-value <0.05 was considered statistically significant. Results: We identified 83 patients who received durvalumab after CXRT for treatment of stage 3 unresectable NSCLC. Baseline characteristics are provided in table 1. Among all the tumors, 25% had a PDL-1 <1%. 33% of the study population received durvalumab less than 30 days after CXRT and 67% received it after 30 days. The mOS was not impacted by race, sex, or tumor hisotology. Compared to higher PDL-1 percentage, patients with PD-L1 <1% had a statistically significant lower survival probability. At 14 months, 87% of patients with a PD-L1 <1% were alive compared to 100% in those with a PD-L1 1-50% or a PD-L1 >50%. Less than 35% of patients with PD-L1 <1% survived beyond 30 months compared to 45% for PD-L1 1-50% and 100% for PD-L1 >50% (p-value 0.02). Patients who received durvalumab 30-60 days after concurrent CXRT had a lower OS at 30 months compared to those who started before 30 days (44% versus 90%). However, statistical significance was not reached (p-value 0.45). Conclusions: This study demonstrates that patients with a PD-L1 tumor expression of <1% had a statistically significant lower survival probability compared to those with a PD-L1 expression of 1-50% and > 50% in this patient population. Time from CXRT to the start of durvalumab was not shown to affect survival outcomes.