The mutational pattern of DNA damage repair pathway in pancreatic cancer patients.

Abstract

e16293 Background: Besides BRCA1/2, there are various genes involved in DNA damage repair that could predict patients’ response to treatments such as platin-based therapy, PARP inhibitors, and immunotherapy. While the mutational pattern of DNA damage repair (DDR) gene alterations in pancreatic patients remains unknown. Methods: Tumors and blood samples from 490 pancreatic patients were analyzed with next-generation sequencing (NGS) that covered 808 genes. Patients were classified based on the presence or absence of deleterious mutations across a panel of 98 DDR genes. Results: 70.4% (345/490) pancreatic cancer patients harbored DDR gene pathogenic mutations (mut). Among DDR-mut patients, 84.6% (292/345) had only somatic DDR gene alterations, 6.4% (22/345) had only germline DDR gene alterations, and 9.0% (31/345) had both. The most frequently mutated somatic DDR genes were TP53 (73.9%), CDKN2A (17.1%), ARID1A (10.1%), ATM (4.1%), and BRCA2 (4.1%). The most commonly mutated germline DDR genes were BRCA2 (4.1%), RAD51B (2.0%), ATM (2.0%), FANCE (0.9%), PALB2 (0.9%). Among the functional pathways of DDR genes, the most commonly mutated pathways were others (77.2%), FA (10.1%), CCC (7.7%), HR (1.5%), NHEJ (1.4%), MMR (1.4%), and BER (0.8%). No patients were found to harbor mutations in NER, TLS, and DR pathways. In addition, the mean TMB was significantly higher in the DDR-mut group compared with the wild-type DDR (wt) group (6.2 vs. 5.0 muts/Mb; p < 0.05). No significant difference in microsatellite instability was observed between DDR-mut and DDR-wt patients (p = 0.67). In terms of HRD status, 87.5% (28/32) HRD-positive patients and 73.1% (19/26) HRD-negative patients had DDR gene mutations. No significant difference in DDR variants was found between HRD-positive and HRD-negative patients, suggesting that HRD detection is necessary for DDR-mut patients. Within individual DDR genes, CDKN2A mutation was significantly associated with HRD-positivity (p < 0.05) whereas BRCA1, BRCA2, ATM, and PALB2 were not. Conclusions: An expanding set of DDR genes profiling provides more therapeutic opportunities for pancreatic patients who might benefit from PARP inhibitor owing to pathogenic mutations in DDR genes. This retrospective study may serve as a benchmark for the future design of an expanded association study between DDR mutations and the therapeutic outcome of pancreatic cancer.