Identification of DNA repair/replication genes mutations in determining response to immune checkpoint inhibitors in non-small cell lung cancer patients.

Abstract

e14582 Background: Tumor mutational burden (TMB) is considered a promising predictive biomarker for immune checkpoint blockade (ICB) therapy response . However, the measurement of TMB relies on the whole-exome sequencing (WES), which is technically limited by sample volume and freshness, thus restricts its use in clinical practice. Since TMB is controlled by the balance between DNA damage and the repair, it is a rational approach to identify a subset of DNA repair/replication gene mutations associated with increased TMB as a surrogate, which could be monitored in clinic to predict ICB efficacy even busing limited archived tissues. Methods: The mutation status of 471 genes associated with DNA repair and replication were analyzed for the correlation with TMB and/or ICB therapeutic responses in three cohorts of NSCLC patients, which are: Cohort A, WES data of 100 Chinese NSCLC patients; Cohort B, WES data of NSCLC patients from TCGA database; Cohort C, WES data and therapeutic response to PD-1 mAb from a Science paper (Rizvi et al. 2015, Science). Results: We identified somatic mutations in 32 DNA repair/replication genes associated with high TMB in both Cohort A and Cohort B. In Cohort C, mutations were found in 20 out of these 32 genes, and the mutation status of 17/20 genes were associated with the clinical benefit of ICB therapy. Noteworthy, mutations of TP53, POLQ, MMS22L, HERC2, CEP164, BRCA1/2, FANCM and MSH4 were mostly common mutations associated with TMB in all 3 cohorts, and ERCC2 and ERCC6 were uniquely high mutated and associated with high TMB in Chinese Han people from Cohort A. Interestingly, EGFR activating mutations were inversely correlated with both high TMB and good ICB response. Conclusions: This retrospective study identified 17 DNA repair/replication-related genes, whose mutation status was associated with high TMB and/or ICB response. Mutational patterns of DNA repair genes are likely different between western and Chinese NSCLC patient population. The data also suggested that NSCLC patients carrying EGFR activating mutations are not preferential population for ICB therapy. Further data is needed to verify the validity of these observations.