Nevertheless, several factors predictive of response to PD-1/PD-L1 therapy have been identified, such as PD-1/PD-L1 expression, gut microbiome, antigen recognition, mismatch repair (MMR), microsatellite instability (MSI), tumor-infiltrating immune cells, and tumor mutation burden (TMB) [38]. Here, PDCD1 is linked to neoplasm.