Efficacy and Safety Profile of PD-1 Inhibitors Versus Chemotherapy in the Second-Line Treatment of Advanced Esophageal Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Programmed death 1 (PD-1) inhibitors have emerged as the new standard of care for the second-line treatment of advanced esophageal squamous cell carcinoma. There have been lots of research lately concerning the topic. A comprehensive assessment of the efficacy and safety profile between PD-1 inhibitors and chemotherapy is warranted. Hence, we carried out a systematic review and meta-analysis to illustrate this issue. Pubmed, Embase, Cochrane Library, and Embase were searched systematically until May 1, 2022. We extracted data on efficacy and safety and calculated the pooled hazard ratios (HRs) and relative ratios (RRs) with 95% CI using randomized-effect or fixed-effect models. A subgroup analysis was applied to explore the factors modifying the response to PD-1 inhibitors. Ultimately, a total of 5 studies involving 1970 patients were included in our meta-analysis. PD-1 inhibitors group could attain greater overall survival (OS) benefit (HR = 0.73, 95% CI: 0.66-0.81, P < 0.001) and nearly favorable progression-free survival (HR = 0.89, 0.76-1.04, P = 0.13). Treatment-related adverse events (RR = 0.76, 95% CI: 0.64-0.91, P = 0.004) and level 3-5 treatment-related adverse events (RR = 0.40, 95% CI: 0.32-0.49, P < 0.001) were significantly diminished in PD-1 inhibitors groups. Among all modifying factors, programmed death ligand 1 combined positive score was positively associated with the patient's OS. The analysis suggests that PD-1 inhibitors exhibited better survival outcomes and safety profiles than standard-of-care chemotherapy. High levels of programmed death ligand 1 combined positive scores were associated with an enhanced response to PD-1 immunotherapies concerning OS.