As PD-L1 expression is regulated by the upstream signaling pathway, while PD-L1/PD-1 combination is transferred to the downstream T cell regulation as the second signal, the expression level of relevant genes in regulating PD-L1 expression and in PD-1 checkpoint pathway in cancer appears to be of vital importance, which may indicate the potential sensitivity of the tumor to radiotherapy. Here, PDCD1 is linked to cancer.