CTLA4 and neoplasm: A single dose of radiation was chosen to simplify the timing of immune therapy relative to radiation, while 20Gy was chosen given the in vivo radioresponse of CT26 tumors13 and data demonstrating dose-dependent increase in MHC I expression and antigen presentation.[2],[3] Anti-CTLA4 treatment alone had little effect on tumor growth (Fig 1B) and resulted in a small survival benefit with a median survival of 32 days versus 28 days in the no treatment (NT) control group (p = 0.03) (Fig 1C).