Search Method
This meta-analysis was conducted in term of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) Updating guidance(16). This research was registered in PROSPERO and ID was CRD42021281619. Two researchers (xing cao and yafei wang) searched in PubMed, EMBASE, and Cochrane Library independently for related electronic literatures without language restrictions (updated in September 2021). The comprehensive search strategy combined Medical Subject Headings (MeSH) terms with Entry Terms. Take PubMed for example, Proton Pump Inhibitors is MeSH, the Entry Terms in PubMed included the following: “Inhibitors, Proton Pump,” “Proton Pump Inhibitor,” “Inhibitor, Proton Pump,” and “Pump Inhibitor, Proton.” The same search strategy was applied in immune checkpoint inhibitors and merged two results by “AND”. The detailed search formula was presented in supplementary due to its prolixity.