PD-L1 score as a prognostic biomarker in Asian patients with early-stage, EGFR-mutated lung cancer.

Abstract

8527 Background: Adjuvant Atezolizumab was recently approved in stage II-IIIA non-small cell lung cancer (NSCLC) with PD-L1 ≥1%. However, disease-free survival (DFS) benefit was mainly driven by PD-L1 ≥50% and among EGFR-mutated subgroup, atezolizumab did not demonstrate DFS benefit when PD-L1 0% patients were included. We sought to determine the prognostic value of PD-L1 score in early-stage EGFR-mutated NSCLC. Methods: Consecutive patients with Stage IA-IIIA NSCLC diagnosed 1/1/2010 – 31/12/2019 who underwent curative surgery at National Cancer Centre Singapore with evaluable EGFR and PD-L1 status were included. Co-primary endpoints were 2-year DFS and 5-year overall survival (OS) by Kaplan-Meier method. Results: 455 patients were included (267 EGFR-mutant; 188 EGFR-wildtype). Median age at diagnosis was 65 years, 52.3% (238/455) were males and 62.9% (286/455) were never-smokers. Adenocarcinomas comprised 92.1% (419/455) and 92.5% (421/455) had R0 resection. Stage IA comprised 42.4% (193/455), Stage IB 23.1% (105/455), Stage II 15.8% (72/455) and Stage IIIA 18.7% (85/455). Among EGFR-mutant, 45.3% (121/267) were Ex19del and 41.9% (112/267) were L858R. PD-L1 ≥1% among EGFR-mutant and EGFR-wildtype was 55.8% (149/267) and 60.1% (113/188) respectively (p = 0.361). PDL1 ≥50% was significantly associated with higher stage at diagnosis among EGFR-mutant (p < 0.001) but not EGFR-wildtype (p = 0.319). At median follow up of 47 months, 178 patients had relapsed. Among EGFR-mutant, 2-year DFS comparing PD-L1 0% and PD-L1 ≥1% was 79.0% and 68.9% (p = 0.006) while 5-year OS was 87.6% and 70.6% (p = 0.006) respectively. 2-year DFS and 5-year OS by PD-L1 tertile (as shown in table) revealed that higher PD-L1 score was prognostically worse for both DFS and OS among EGFR-mutant. A similar trend was observed among EGFR-wildtype but did not reach statistical significance, apart from PD-L1 ≥50% which had significantly inferior DFS. Conclusions: Higher PD-L1 score was significantly associated with worse DFS and OS among early-stage EGFR-mutated NSCLC, possibly due to higher stage at diagnosis among PDL1 ≥50%. Our study highlights the poor prognosis of PDL1 ≥50% EGFR-mutated NSCLC in a pre-osimertinib era and underscores the importance of personalised risk-stratified adjuvant strategies. [Table: see text]