Comprehensive next-generation sequencing to portray distinctive molecular characteristics of hypermutant lung cancer.

Abstract

e15255 Background: Tumor mutation burden (TMB) has been confirmed to predict the sensitivity to immunotherapy across multiple tumor types. Multiple genetic factors have been confirmed to increase the level of TMB, such as mutations in DNA damage repair (DDR) genes, POLE/POLD1, and high microsatellite instability (MSI). However, the extent that these factors contribute to hypermutation in lung cancer has not been fully investigated. Methods: We retrospectively reviewed the genetic profiles of 1000 lung cancer patients (pts) who underwent 1021-panel matched tumor-normal next-generation sequencing using tumor tissue samples and peripheral blood. Their TMB status were analyzed to determine the threshold of hypermutation. The clinicopathological characteristics, genetic profiles and genetic factors related to hypermutation were investigated for the pts in hypermutant cohort. Results: The threshold of hypermutation was determined as 19 muts/MB (top 5% in 1000 pts). As a result, 53 pts were included in the hypermutant cohort. A total of 1725 nonsynonymous somatic variants in 506 genes were identified. The most frequently mutated genes included TP53 (88.7%), LRP1B (71.7%), MLL2 (35.8%), EPHA5 (34.0%), and FAT1 (34.0%). KRAS was mutated in 17% pts, whereas mutations in EGFR, BRAF, ERBB2, MET were identified less commonly. MSI-high was observed in 5 cases. A germline mutation in BRCA1 gene was identified in an adenocarcinoma patient. Compared to genetic profiles of non-small cell lung cancer from TCGA database, mutations in multiple DDR genes were enriched in the hypermutant cohort (Table). No known driver mutation in POLE/POLD1 was identified. Conclusions: MSI-high and mutations in DDR genes may be associated with high level of TMB, whereas POLE/POLD1 driver mutations may not be related to hypermutant lung cancer. Hypermutant lung cancer displays distinctive molecular features that may be used as complementary indicators to screening pts sensitive to immunotherapy. [Table: see text]