In addition, since the PD-1 inhibitor acts with an antitumor role through inhibiting the PD-1 expression in T cells, thus its hematological toxicity is non-neglectable: a previous study reveals that the occurrence of grade 3–4 adverse events is low, which mainly includes leukopenia, neutropenia, pneumonitis, cholangitis, neuropathy, and hypokalemia (13). This evidence concerns the gene PDCD1 and Hypokalemia.