Abstract
BACKGROUND: Clinical efficacy of immune checkpoint inhibitors (ICIs) for non-small cell lung cancer (NSCLC) with uncommon histology (uNSCLC) is unknown. METHODS: Patients with NSCLC treated with ICI monotherapy between January 2014 and December 2018 in 10 Japanese hospitals were retrospectively evaluated. The patients were divided into: (1) NSCLC with common histology (cNSCLC), defined as adenocarcinoma and squamous cell carcinoma; and (2) uNSCLC, defined as incompatibility with morphological and immunohistochemical criteria for adenocarcinoma or squamous cell carcinoma. Propensity score matching was performed to balance the two groups. RESULTS: Among a total of 175 patients included, 44 with uNSCLC (10 pleomorphic carcinomas, 9 large cell neuroendocrine carcinomas, 2 large cell carcinomas, and 23 not otherwise specified) and 44 with matched cNSCLC (32 adenocarcinomas and 12 squamous cell carcinomas) were selected for analyses. Median progression-free survival (PFS) (4.4 months, 95% confidence interval [CI] 1.8-7.7 months) and overall survival (OS) (11.4 months, 95% CI 7.4-27.4 months) in the uNSCLC patients were not significantly different from those in matched cNSCLC patients (5.4 months, 95% CI 3.1-7.6 months, p = 0.761; and 14.1 months, 95% CI 10.6-29.6 months, p = 0.381). In multivariate analysis, Eastern Cooperative Oncology Group performance status (ECOG-PS) of 0-1 and programmed death ligand-1 (PD-L1) expression were predictive for PFS and OS in uNSCLC. CONCLUSIONS: ICIs had similar clinical efficacy for treatment of uNSCLC and cNSCLC. Good ECOG-PS and PD-L1 expression were predictive for efficacy of ICIs in uNSCLC.