Though PD-L1/PD-1 ICIs are suggested for metastatic NSCLC patients whose tumors strongly express PD-L1 (tumor proportion scores ≧50%), more than 50% of tumors with strong PD-L1 expression do not respond to PD-1/PD-L1 inhibitors [47,49]. Here, PDCD1 is linked to non-small cell lung carcinoma.