DNA Repair gene alterations and efficacy from gemcitabine and nab-paclitaxel with/without durvalumab and tremelimumab in metastatic pancreatic ductal adenocarcinoma.

Abstract

The CCTG PA.7 study was a randomized phase II trial comparing chemotherapy with and without dual immune checkpoint inhibition in patients with metastatic pancreatic ductal adenocarcinoma (mPDAC). In follow-up to the published primary results of the trial, the analysis herein focused on long-term survival and exploratory analysis.Plasma sequencing analysis identified concurrent mutations in DNA damage repair genes BRCA1, POLE, ATM and FANCA in 18/173 (10.40%) of patients, and presence of two or more mutations in these genes was associated with overall survival benefit for patients receiving immunotherapy (median overall survival 26.2 vs. 9.7 months; hazard ratio, 0.34; 95% CI, 0.16-0.68; p = 0.001; interaction p = 0.003). Partial response was observed in 7/11 (63.64%) patients with concurrent DNA damage repair gene mutations in the immunotherapy arm. As a prospective study in PDAC identifying a potential biomarker beyond mismatch repair deficiency for benefit from immunotherapy, these data highlight an actionable subgroup of mPDAC.