Adjuvant Pembrolizumab in Patients with Stage IIIA/N2 Non-Small Cell Lung Cancer Completely Resected after Neoadjuvant Concurrent Chemoradiation: A Prospective, Open-Label, Single-Arm, Phase 2 Trial.

Purpose:Optimal treatment for stage IIIA/N2 non-small cell lung cancer (NSCLC) is controversial. We aimed to assess the efficacy and safety of adjuvant pembrolizumab for stage IIIA/N2 NSCLC completely resected after neoadjuvant concurrent chemoradiation therapy (CCRT). Materials and Methods:In this open-label, single-center, single-arm phase 2 trial, patients with stage IIIA/N2 NSCLC received adjuvant pembrolizumab for up to two years after complete resection following neoadjuvant CCRT. The primary endpoint was disease-free survival (DFS). Secondary endpoints included overall survival (OS) and safety. As an exploratory biomarker analysis, we evaluated the proliferative response of blood CD39+PD-1+CD8+ T cells using fold changes in the percentage of proliferating Ki-67+ cells from days 1 to 7 of cycle 1 (Ki-67D7/D1). Results:Between October 2017 and October 2018, 37 patients were enrolled. Twelve (32%) and three (8%) patients harbored EGFR and ALK alterations, respectively. Of 34 patients with programmed cell death ligand 1 assessment, 21 (62%), 9 (26%), and 4 (12%) had a tumor proportion score of <1%, 1-50%, and ≥50%, respectively. The median follow-up was 71 months. The median DFS was 22.4 months in the overall population, with a five-year DFS rate of 29%. The OS rate was 86% at two years and 76% at five years. Patients with tumor recurrence within six months had a significantly lower Ki-67D7/D1 among CD39+PD-1+CD8+ T cells than those without (p=0.036). No new safety signals were identified. Conclusion:Adjuvant pembrolizumab may offer durable disease control in a subset of stage IIIA/N2 NSCLC patients after neoadjuvant CCRT and surgery.