Background and objective Immune checkpoint inhibitor (ICI) therapies have shown promising prospects in colorectal cancer (CRC) immunotherapy; many clinical trials have been carried out. In this study, we sought to evaluate the efficacy and safety of ICI therapies in CRC by presenting a meta-analysis of relevant studies. Methods Databases including PubMed, Embase, Cochrane Library, and Web of Science were systematically searched for studies concerning the efficacy and safety of ICI in colorectal cancer. The reported odds ratio (OR) or weighted mean difference (WMD) with 95% confidence intervals (CIs) of overall survival (OS), progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), treatment-related adverse events (TRAEs), and TRAEs ≥ 3 in the included studies were analyzed by fixed effects/random effects models. Results Three studies involving 667 patients with colorectal cancer were included in our meta-analysis. No significant difference between the immune checkpoint inhibitor therapies and conventional therapies in OS (WMD = 0.73, 95% CI − 3.09, 4.54; p = 0.71), in ORR (OR = 1.54, 95% CI 0.98, 2.40; p = 0.06), and in DCR (OR = 0.97, 95% CI 0.36, 2.61; p = 0.95). The median PFS of the ICI therapy group was shorter than that of the conventional therapy group (WMD = − 0.10, 95% CI − 0.18, − 0.02; p = 0.02). At the same time, we also could not find a significant difference between the immune checkpoint inhibitor therapies and conventional therapies in TRAEs (OR = 1.56, 95% CI 0.11, 22.09; p = 0.74) and in TRAEs ≥ 3 (OR = 0.94, 95% CI 0.16, 5.65; p = 0.95). Conclusion Immune checkpoint inhibitor therapies could not improve all survival endpoints to advanced or metastatic colorectal cancer patients. Whether immune checkpoint inhibitors should be the first choice of therapies for colorectal cancer patients with undetermined microsatellite status or not able to determine microsatellite status needs more related studies to prove.
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