LAUSR

39Background: Indications for Nivolumab (NIVO), a checkpoint inhibitor immunotherapy drug, in treating a variety of metastatic malignancies has markedly increased. Radiation therapy (RT) is also commonly used in this patient population, however, there are limited data on the safety profile of combined RT-NIVO. We reviewed our experience to assess the acute toxicity profile of concurrent RT-NIVO. Methods: All consecutive patients who received NIVO from 1/2015 to 5/2017 at 4 centers across 2 institutions were retrospectively reviewed. Those patients who completed a course of RT from 1 day prior to initial NIVO infusion through 1 month after last NIVO infusion were considered to have received concurrent therapy and included in the subsequent analysis. Descriptive statistics are reported for patient/tumor/treatment characteristics and observed acute toxicities within 3 months of RT completion. Results: Among 261 patients who received NIVO, 46 (17.6%) received concurrent RT to 67 different sites. The median f/...