DNA damage response gene alterations are associated with high tumor mutational burden and clinical benefit from programmed death 1 axis inhibition in non-small cell lung cancer.

Abstract

9077 Background: DNA damage response (DDR) gene alterations are associated with increased tumor infiltrating lymphocytes, higher genomic instability, and higher tumor mutational burden (TMB) in cancer. Whether DDR alterations are associated with benefit from immune-checkpoint inhibitors (ICIs) in non-small cell lung cancer (NSCLC) is unknown. Methods: Clinicopathologic and genomic data were collected from patients (pts) with advanced NSCLC at the Dana-Farber Cancer Institute treated with PD-(L)1 inhibitors. Targeted next-generation sequencing (NGS) by OncoPanel was used to determine DDR gene mutation status and TMB. DDR positive (DDRpos) cases were defined as those with pathogenic DDR alterations (per COSMIC and ClinVar databases). DDR negative (DDRneg) cases were defined as either DDR wild-type or those with non-pathogenic DDR alterations. Results: Of 468 pts with successful NGS who received ICIs, 242 (51.7%) were identified as having any DDR alteration. Of them, 74 (15.8% in the entire cohort) were defined as DDRpos with pathogenic alterations in the following genes: ATM (41.9%), MLH1/MSH2/MSH6 (18.9%), BRCA1/2 (16.2%), CHEK1/2 (9.4%), FANC genes (9.4%), BAP1 (5.4%), RAD genes (5.4%), ERCC4/6 (4.0%), POLE (2.7%), ATR (2.7%). DDRpos and DDRneg groups were balanced in terms of age, performance status, gender, histology, oncogenic driver mutation, smoking status, ICI line, baseline brain metastases. The median TMB was significantly higher in the DDRpos group compared to the DDRneg group (12.1 vs 9.8 mutations/megabase, P = 0.007). No difference in median PD-L1 tumor proportion score was observed between groups (30% vs 25%, P = 0.33). Compared to DDRneg pts (N = 394), DDRpos pts had a significantly higher objective response rate (31.1% vs 19.1%, P = 0.03), and longer median progression-free survival (4.3 vs 2.6 months, HR: 0.71 [95%CI: 0.53-0.95], P = 0.02) and overall survival (16.3 vs 9.8 months, HR: 0.63 [95%CI: 0.45-0.89], P = 0.009) with PD-(L)1 therapy. Conclusions: Pathogenic DDR alterations are frequent in NSCLC and are associated with higher TMB and improved clinical outcomes in NSCLC pts treated with PD-1 axis inhibition.