DNA response and repair gene mutations as a signature for pembrolizumab response in never-smoker non-small lung cancer: real word approach and patient similarity network analysis

Purpose: Single-agent immune checkpoint inhibitor (IO) therapy is the standard of care for non-oncogene addicted advanced non-small cell lung cancer (aNSCLC) with PD-L1 ≥ 50%. High tumor mutation burden (H-TMB) is a notable biomarker for IO response. Smoking-induced harm generates H-TMB in smoking aNSCLC patients (S-pts), whereas never-smoking patients (NS-pts) usually have low TMB and are IO-unresponsive. However, NS-pts with H-TMB have not been well molecularly characterized. Experimental design Clinical data of 142 aNSCLC patients with PD-L1 ≥ 50% treated with first-line pembrolizumab were retrospectively collected. Next-generation sequencing was performed using the FoundationOne®CDx assay to correlate genomic alterations with clinical characteristics and response outcomes. Detected mutations were classified into eleven main pathways: cell cycle, Hippo, Myc, Notch, oxidative stress/Nrf2, PI3K, RTK/RAS/MAP, TGF-b, p53, b-catenin/Wnt, and DDR. Enrichment analysis was performed on pathways with at least one mutation per patient to characterize patient subgroups based on mutated pathways. Moreover, to further investigate the molecular characterization of patients’ subgroups, we built and analyzed the patient similarity network exploiting the mutational profile to compute the pairwise similarity between patients. Results: There were 111 S-pts and 31 NS-pts; S-pts had higher TMB (median TMB: 8 vs. 4 Mut/Mb). However, 11 NS-pts had high TMB (median TMB: 16.39 Mut/Mb) and were significantly enriched in b-catenin/Wnt and DDR pathway mutations (p-values=0.0027 and 0.0014, respectively) compared to others and H-TMB/S-pts. Using publicly available molecular characterization data (of 853 NSCLC patients from 2 randomized controlled trials), DDR pathway mutations were confirmed to be enriched in NS-pts with H-TMB. In the real world cohort the subgroup of H-TMB/NS-pts with DDR pathway mutation showed better IO response and survival. Moreover, the similarity network analysis of the NS-pts revealed the presence of one subgroup characterized by high TMB, improved OS and a prevalence of DDR pathway mutations. Conclusions: DDR signature has a potential role as additional generator of H-TMB in NS-pts. This subgroup of IO-responsive NS-pts may have better prognosis.