Tumor PD-L1 expression is associated with outcomes in stage 3 NSCLC patients treated with consolidation durvalumab

Background: Durvalumab is an anti-PD-L1 immune checkpoint inhibitor approved for consolidation therapy for patients with stage III non-small cell lung cancer (NSCLC) after chemoradiation. The purpose of our study was to evaluate the association between the degree of tumor PD-L1 expression and outcomes of stage III NSCLC patients treated with durvalumab. Methods: We conducted a retrospective analysis of all the patients who received durvalumab between July 2017 and July 2019 at our facilities and were diagnosed with or progressed to Stage III NSCLC before durvalumab consolidation. Patients were divided into groups based on the degree of PD-L1 expression: <1%, 1-49%, and 50-100%. Overall survival and progression-free survival were estimated by the Kaplan-Meier method and the Multivariate Cox proportional hazard model was used to assess the effect of PD-L1 expression level on OS and PFS, adjusting for age and gender. Results: We identified 121 patients with stage III NSCLC that underwent durvalumab consolidation. Of them, 29.8% had PD-L1 expression of 50-100%, 24.8% had PD-L1 expression of 1-49%, and 27.3% had PD-L1 expression of <1%, while 18.2% were not tested for PD-L1 expression. The rate of cancer progression in the group with 50-100% PD-L1 expression was 16.7% compared to 60% in the 1-49% expression group and 54.6% in the <1% expression group, and the 1-year survival rates were higher in the 50-100% group (97%) compared to the 1-49% group and the <1% group (73% and 78%, respectively; P=0.028). Survival analysis via Kaplan-Meier revealed a significant difference in both PFS (P<0.0001) and OS (P<0.028) based on the extent of PD-L1 expression. Multivariate analysis revealed that a PD-L1 expression >50% was the only factor that was significantly associated with improved PFS (HR=0.205, P=0.0004) and OS (HR=0.339, P=0.04). Conclusions: Our study demonstrated that patients whose tumors had >50% PD-L1 expression had significantly longer progression-free survival and overall survival than those with lower PD-L1 expression. This suggests that the degree of tumor PD-L1 expression may play a role in predicting benefit from durvalumab for these patients.