AbstractBackgroundMutations in genes involved in DNA damage repair (DDR), a hallmark of cancer, are associated with increased cancer cell sensitivity to certain therapies. This study sought to evaluate the association of DDR pathogenic variants with treatment efficacy in patients with advanced non‐small cell lung cancer (NSCLC).MethodsA retrospective cohort of consecutive patients with advanced NSCLC attending a tertiary medical center who underwent next‐generation sequencing in 01/2015‐8/2020 were clustered according to DDR gene status and compared for overall response rate (ORR), progression‐free survival (PFS) (patients receiving systemic therapy), local PFS (patients receiving definitive radiotherapy), and overall survival (OS) using log‐rank and Cox regression analyses.ResultsOf 225 patients with a clear tumor status, 42 had a pathogenic/likely pathogenic DDR variant (pDDR), and 183 had no DDR variant (wtDDR). Overall survival was similar in the two groups (24.2 vs. 23.1 months, p = 0.63). The pDDR group had a higher median local PFS after radiotherapy (median 45 months vs. 9.9 months, respectively; p = 0.044), a higher ORR (88.9% vs. 36.2%, p = 0.04), and a longer median PFS (not reached vs. 6.0 months, p = 0.01) in patients treated with immune checkpoint blockade. There was no difference in ORR, median PFS, and median OS in patients treated with platinum‐based chemotherapy.ConclusionOur retrospective data suggest that in patients with stage 4 NSCLC, pathogenic variants in DDR pathway genes may be associated with higher efficacy of radiotherapy and immune checkpoint inhibitors (ICIs). This should be further explored prospectively.