Although existing researches have suggested correlations between PD-L1 expression or PD-1/PD-L1 interaction, tumor mutation burden, and tumor-infiltrating lymphocytes with anti-PD-1/PD-L1 therapy efficacy [49, 50], no biomarker has been identified that is sufficient to stratify patients who would benefit from immunotherapy effectively. Here, PDCD1 is linked to neoplasm.