PD-L1 expression and progression risk of stage III NSCLC patients on durvalumab consolidation.

Abstract

e21070 Background: Durvalumab is an anti-PD-L1 agent used as consolidation for patients with stage III non-small cell lung cancer (NSCLC) following chemoradiation. In the PACIFIC trial similar progression-free survival (PFS) and overall survival (OS) benefits were seen whether patients had PD-L1 expression of ≥25% or <25%. In this study we sought to examine outcomes for patients with PD-L1 expression using the more commonly used <1%, 1-49%, and 50-100% cutoff points. Methods: This was a retrospective analysis of 52 patients with stage III NSCLC who underwent treatment with chemoradiation followed by durvalumab maintenance. Patients were divided into groups of PD-L1 Negative (<1% positivity), Low PD-L1 (1-49%), and High PD-L1 (50-100%) based on the percentage of tumor PD-L1 expression using local testing with the Dako 22C2 antibody. The primary endpoint was presence or absence of radiographic progression while on durvalumab or after completing therapy, while PFS and OS were also determined. Results: Of the 52 patients, 25% were in the High PD-L1 group, 21% in the Low PD-L1 group, 27% in the PD-L1 Negative group, and the remaining were not tested for PD-L1. The progression rates were 64.3%, 90.9%, and 23.1% for the PD-L1 Negative, Low PD-L1, and High PD-L1 groups respectively (Table). Using Chi-square analysis there was a significant association between the extent of PD-L1 expression and progression (p = 0.003). The odd’s ratio (OR) of progression in the High PD-L1 group compared to the PD-L1 Negative group was 0.167 (0.031-0.904, p = 0.038), and the OR of progression in the Low PD-L1 group compared to PD-L1 Negative was 5.556 (0.541-57.00, p = 0.149). There was a statistically significant difference in PFS between the groups (p = 0.019), but not OS. Conclusions: Our results show that PD-L1 expression may be useful in predicting the risk of cancer progression in stage III NSCLC patients undergoing durvalumab consolidation. Patients with high PD-L1 (50-100%) expression had significantly lower odds of disease progression and longer PFS compared to those who were negative for PD-L1. While the rate of progression was higher in the Low PD-L1 group, the OR was not statistically significant when compared to the PD-L1 Negative group. [Table: see text]