Data extraction

Two investigators (Oliver O, Liu YY) independently reviewed the eligible studies and extracted data from each study. Extracted variables included title, first author, year of publication, number of participants, type of immunotherapy received, GM analysis method, and study outcomes (GM composition and diversity in responders/non-responders and ICB-related colitis/non-ICB-related colitis patients). Extracted GM composition data included a list of the GM at the level of phyla, class, order, family, genus and species, whereas extracted GM diversity extracted included alpha diversity or the Shannon index. Any discrepancies found by the investigators on data extraction were resolved by consensus. In addition, we conducted a relevant search by Reference Citation Analysis (RCA) (https://www.referencecitationanalysis.com).