PDCD1 and melanoma: In melanoma and breast cancer models, the combination of hypo-fractionated regimen of 3 × 9.18 Gy in 3 or 5 days, and 5 × 6.43 Gy in 10 days with an anti-PD-1 antibody, resulted in growth inhibition of both irradiated primary and non-irradiated tumors [12].