PDCD1 and neoplasm: Mouse studies showed that the addition of anti-PD1 to radiation provided the greatest tumor control (both primary and contralateral non-irradiated tumors) compared to anti-PD1 with chemotherapy by increasing the ratio of CD8 T cells to Treg cells and decreasing T cell exhaustion in both the primary and contralateral implanted tumors in mice with esophageal cancers [16].