Clinical utility of BRCA and ATM mutation status in circulating tumour DNA for treatment selection in advanced pancreatic cancer

Abstract

Identification of homologous recombination deficiency (HRD) remains a challenge in advanced pancreatic cancer (APC). We investigated the utility of circulating tumour DNA (ctDNA) profiling in the assessment of BRCA1/2 and ATM mutation status and treatment selection in APC. We analysed clinical and ctDNA data of 702 patients with APC enroled in GOZILA, a ctDNA profiling study using Guardant360. Inactivating BRCA1/2 and ATM mutations were detected in 4.8% (putative germline, 3.7%) and 4.4% (putative germline, 0.9%) of patients, respectively. Objective response (63.2% vs. 16.2%) and PFS (HR 0.55, 95% CI 0.32–0.93) on platinum-containing chemotherapy were significantly better in patients with putative germline BRCA1/2 (gBRCA) mutation than those without. In contrast, putative gBRCA mutation had no impact on the efficacy of gemcitabine plus nab-paclitaxel. In 2 patients treated with platinum-containing therapy, putative BRCA2 reversion mutations were detected. Three of seven patients with somatic BRCA mutations responded to platinum-containing therapy, while only one of four with putative germline ATM mutations did. One-third of somatic ATM mutations were in genomic loci associated with clonal haematopoiesis. Comprehensive ctDNA profiling provides clinically relevant information regarding HRD status. It can be a practical, convenient option for HRD screening in APC.