A phase II study of ipilimumab and nivolumab with radiation in metastatic pancreatic adenocarcinoma.

391Background: Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal cancer. Immunotherapy (IO) has shown minimal activity. In preclinical models, radiation (XRT) increases likelihood of response to IO via an abscopal effect where local tx (treatment) of a tumor leads to an antitumor response distantly, with synergy between XRT and dual checkpoint blockade. In this study, we assessed CTLA-4 and PD-1 blockade with XRT as a strategy to stimulate an immune response for patients (pts) with PDAC. Methods: In this open-label, single arm phase-2 study, we enrolled 25 metastatic PDAC pts in an exploratory cohort. Eligible pts had histologically-confirmed PDAC, ECOG PS 0-1, and progression on at least 1 line of tx. Tx consisted of Ipilimumab (1 mg/kg every 6 wks), Nivolumab (240 mg every 2 wks) and 3 fractions of 8 Gy of XRT at cycle 2. Tx continued until PD, discontinuation or withdrawal. Endpoints include Disease Control Rate (DCR), ORR, PFS, OS and safety. Radiological evaluations were every 3 months....