PDCD1 and neoplasm: On day four of the tracer injection, a treatment response to the anti-PD-1 antibody and radiotherapy was observed: the IR/anti-PD-1 mAb-treated tumor volume decreased (tumor volume approx. 80 mm3) compared to that of the non-IR/anti-PD-1 mAb and IR/isotype mAb (both approx. 150 m3) and non-IR/isotype mAb (approx. 280 m3) treatments.