PDCD1 and neoplasm: Addition of a PD-1 inhibitor to SABR resulted in synergistic antitumor activity on the primary tumor compared to PD-1 inhibitor or SABR alone and recapitulated abscopal effects on secondary nonirradiated tumors in PD-1-WT mice when treatment alone with anti-PD-1 or SABR did not reduce secondary tumor growth.