CD274 and non-small cell lung carcinoma: Even though the PD-L1 tumor proportion score has been used as a predictive biomarker in the treatment of advanced NSCLC, it is unclear whether PD-L1 expression in extracranial lesions can be used to select BM patients for ICIs as some studies have suggested a low level of concordance in PD-L1 expression between primary and metastatic sites [61].