An Exploratory Study To Investigate The Immunomodulatory Activity Of Radiation Therapy In Combination With Pembrolizumab In Patients With Renal Cell Cancer.

518Background: Preclinical data suggest there are synergistic effects of radiation therapy (RT) and check point inhibitors in anticancer immunity. The primary objective of this study was to explore the immunomodulatory activity of RT alone or in combination with Pembrolizumab (pembro) in solid tumors including renal cell cancer (RCC) patients (pts). Methods: RCC pts who progressed after at least one front-line therapy were eligible. Pts were treated with either RT (8Gy x 1 or 4Gy x 5) followed by (f/b) pembro or 1 dose pembro f/b RT f/b pembro. Pre- and post RT tumor biopsy was obtained to evaluate PD-L1 expression (assay by QualTeck). Immune markers from peripheral blood before, during, and after treatment were analyzed using flow cytometry. Treatment response was measured based on modified RECIST criteria. Results: 12 RCC patients were enrolled including 2 with non-clear cell subtype. One pt was not evaluable since pt quickly deteriorated and was taken off study. As of September 30, 2016, 5 pts were sti...