We previously showed that PD-L1 expression may be associated with worse survival in pts with NSCLC who undergo surgery. Data are limited on PD-L1 expression in EGFR-mutant NSCLC.
We evaluated the relationship between PD-L1 expression and PFS and OS in 319 pts with EGFR-mutant NSCLC treated at Samsung Medical Center from 2006 to 2014. PD-L1 expression was measured using a market-ready immunohistochemistry (IHC) assay (22C3 antibody). Kaplan-Meier methods, log-rank test, and Cox proportional hazards models were used for survival analysis, adjusting for age, sex, disease stage, smoking history, performance status, and postsurgery chemotherapy or radiotherapy.
Median age was 62 y (range 35-84); 61% of pts were female, 97% had adenocarcinoma, 64% were never smokers, and 48% had stage IA disease; 5% had stage IV disease. Median follow-up was 7 y. 94% of pts underwent resection with curative intent, 43% received postsurgery chemotherapy or an EGFR-TKI (30%), and 18% received radiation. All pts had ≥1 EGFR mutationâ54% in exon 19, including 41% with a deletion, and 39% in exon 21, including 36% with an L858R mutation. One pt had a KRAS mutation. Two pts were also ALK+ by IHC. PD-L1 strong and weak positive were defined as proportion score of ≥50% and 1%-49% of tumor cells, respectively. Overall, 52% of pts were PD-L1 positiveâ8% strong positive and 44% weak positive. The prevalence of PD-L1 positivity was lower among pts with stage I vs stage II-IV disease (44% vs 64%) and among pts with L858R mutation (39%) and exon 19 deletion (52%) than with other EGFR mutations (69%). PD-L1 positivity was associated with worse PFS, with an adjusted hazard ratio of 1.70 (95% CI 0.83-3.47, median 15 mo) for the PD-L1–strong-positive group and 1.68 (95% CI 1.11-2.56, median 21 mo) for the PD-L1–weak-positive group compared with the PD-L1–negative group (median 27 mo). There was no statistically significant association between PD-L1 expression and OS in the adjusted Cox model.
PD-L1 expression is associated with disease stage and type of EGFR mutation. PD-L1 positivity might be associated with worse PFS among pts with surgically treated EGFR-mutant NSCLC. There was no prognostic effect of PD-L1 positivity on OS.
Clinical trial identification
J. Cho, Y.-L. Choi, J.-M. Sun, H. Choi, T.-E. Kim, J. Kim: research grants from Merck & Co., Inc. W. Zhou: Employee of and owns stock in Merck & Co., Inc. Sits on the board of directors of the International Society of Pharmacoepidemiology. M. Dolled-Filhart: Employee of and owns stock in Merck & Co., Inc.
K. Emancipator: Employee of Merck & Co., Inc. Owns stock in Merck & Co., Inc., Johnson & Johnson, and Bayer. Spouse owns stock in Celgene. M.A. Rutkowski: Employee of Merck & Co., Inc.