Data Extraction
Two authors (xing cao and yafei wang) collected data separately from eligible studies. The information relevant to this analysis was extracted: 1. The primary endpoint of investigation were the HRs for PFS and OS (especially OS) among cancer patients receiving ICIs therapy exposed to PPIs or not.2. Secondary variables including the author names, year of publication, country, ICIs agents, tumor type, ICIs treatment line, data from single or multiple centers, PPIs treatment window, study endpoints and number of patients.