CTLA4 and neoplasm: To determine whether pre-existing immunity is necessary for tumor control by checkpoint inhibitors and radiation delivered in an alternative hypofractionated regimen, CT26 tumors were implanted in mice in the presence or absence of anti-CD40L then treated with 8 Gy radiation on 4 consecutive days and treated with anti-CTLA4 delivered in the concurrent timing that has proven superior in this scheme19.