Germline ATM mutations on survival in metastatic pancreatic cancer patients

e16746 Background: Ataxia telangiectasia mutated (ATM) protein is a DNA damage repair enzyme and regulates normal cell-cycle mechanisms. Germline ATM mutations are associated with increased risk for developing pancreatic cancer (PC), occurring in approximately 2% of PC patients (pts). The role of germline ATM mutations in PC is not well defined. The objective of this study was to compare survival outcomes in patients with germline ATM mutations compared to somatic ATM mutations in PC. Methods: Tumor genomic profiling was completed in 144 PC patients at a single institution in the US, where pts were included in the analysis if they had either germline ATM mutations or somatic ATM mutations. Clinical outcomes were compared between pts with germline ATM mutations and pts with somatic ATM mutations only. Adjusted Cox regression models were fit to evaluate the impact of ATM mutation on overall survival (OS), calculated from treatment (tx) initiation to death, and progression free survival (PFS) calculated from tx initiation to first progression. Results: From 144 PC pts evaluated, 7 pts (4.9%) had germline ATM mutations, all of whom presented with metastatic disease, and 14 pts (9.7%) with somatic ATM mutations only, of whom 10 presented with metastatic disease and 4 who initially presented with locally advanced PC. The majority of pts (15/21), including all 7 pts with germline ATM mutations and 8 with somatic ATM mutations, were treated with first line gemcitabine and abraxane. Median OS was not reached in patients with germline mutations, and 11 months for patients with somatic mutations. Pts with germline ATM mutations had significantly higher OS (HR: 0.12, 95% CI 0.03-0.62, p = 0.01) and PFS (HR:0.26, 95%CI 0.07-0.91, p = 0.04) compared to patients with somatic ATM mutations only after adjusting for age, sex, and first-line tx. Conclusions: Pts with germline ATM mutations may experience greater survival benefit from tx compared to those with only somatic ATM mutations. Further research into the underlying mechanism is warranted.