PDCD1 and neoplasm: Lastly, phase I trials of RT and anti-PD-1 therapy have already provided glimpses into potential mechanisms of failure even with the combination as 1 patient with metastatic RCC who rapidly progressed on combined RT and pembrolizumab had biomarker analyses showing an absence of TILs and presence of other nonredundant immune checkpoints in the tumor microenvironment and periphery that may have contributed to treatment failure [149].