Association of Tumor Mutational Burden With DNA Repair Mutations and Response to Anti–PD-1/PD-L1 Therapy in Non–Small-Cell Lung Cancer

Abstract

PurposeTo examine clinical predictors of tumor mutational burden (TMB), to explore the association between TMB and DNA repair mutations, and to analyze TMB as a biomarker for response to immune checkpoint blockade in non–small-cell lung cancer. Patients and MethodsTMB scores were determined retrospectively for 72 consecutive patients at our institution with next-generation sequencing comprehensive genomic profiling testing by Foundation Medicine. TMB scores were correlated with a number of clinical variables and presence of DNA repair mutations. Thirty-four patients were treated with anti–programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) therapies, and survival analyses based on TMB score were performed. In addition, tissue immunohistochemical analysis was performed for a subset of patients. ResultsHistory of smoking, but not other clinical variables, including prior treatment lines, stage of disease, and number of metastatic sites, predicted higher TMB score. Higher TMB score was significantly associated with greater number of DNA repair mutations. In the subset of patients treated with immune checkpoint blockade, higher TMB score significantly predicted overall survival, but not progression-free survival (hazard ratio = 0.10, P = .003; hazard ratio 1.1, P = .84, respectively). In a small subset of patients, PD-1/PD-L1 staining did not independently predict progression-free survival or overall survival. ConclusionTissue TMB was significantly associated with smoking history and number of DNA repair mutations. TMB is a promising biomarker for response to anti–PD-1/PD-L1 therapy, with higher TMB score predicting longer overall survival.