Frequency of discordance in programmed death ligand 1 (PD-L1) expression between primary tumors and paired distant metastases in advanced cancers: A systematic review and meta-analysis.

e14290Background: Randomized trials have demonstrated that PD-L1 expression in tumor cells predicts for response to PD-1 or PD-L1 checkpoint inhibitors in advanced cancers. However, the frequency o...