According to multiple clinical studies and meta-analyses, antibiotic exposure is significantly associated with shortened progression-free survival (PFS) and overall survival (OS) in cancer patients receiving anti-PD-1/PD-L1 therapy, with a PFS hazard ratio (HR) of 1.60 (95% CI: 1.33–1.92, p < 0.00001) and an OS HR of 1.46 (95% CI: 1.32–1.61, p < 0.00001). This evidence concerns the gene PDCD1 and cancer.