Eligible and Exclusion Criteria
Studies that match all the inclusion criteria listed below were selected:1. Population: cancer patients undergoing ICIs therapy alone or in combination;2. Interventions: PPIs were prescribed within a treatment window of 30days before, during or after the first dose of ICIs therapy;3. Comparison: containing an PPIs-exposed group and a control group did not;4. Outcome: intact data that have enough information to calculate HR and their 95% CI for PFS and OS.
Exclusion criteria were as followings:1. Case reports, case series, comments, reviews, letters, editorials, animal models;2. Inappropriate or unknown PPIs treatment window;3. Insufficient information to calculate HRs with 95% CI of PFS or OS;4. Special populations such as veterans. Two authors (xing cao and yafei wang) screened the studies independently and conflicts among them were solved by consensus with a third author.