Abstract

Background: Breast cancer is one of the most prevalent cancers with a high rate of mortality. Immune checkpoint inhibitors (ICIs) have shown promising results in breast cancer treatment. However, the incidences of adverse events (AEs) and immune-related AEs (irAEs) due to ICIs have not been investigated comprehensively. We aimed to determine any-grade and grade 3-5 AEs and irAEs of ICIs compared to the control group which were other conventional therapies in adults with breast cancer. Methods: We included controlled clinical trials that involved ICIs in adults with breast cancer to assess AEs and irAEs of ICIs. We systematically searched PubMed, EMBASE, Scopus, Web of Science, the Cochrane Central Register of Controlled Trials, Clinical-Trials.gov, and metaRegister of Controlled Trials up to March 12, 2021. Version 2 of the Cochrane risk-of-bias tool for randomized trials (RoB 2) was used for quality assessment. Results: Nine studies, including 4687 participants met our inclusion criteria. Rash and infusion reaction were the two most frequent irAEs of any-grade and grade 3-5. Among irAEs, hyperthyroidism had the most prominent difference between the two groups in favor of ICIs followed by hypothyroidism and adrenal insufficiency. Among grade 3-5 and any-grade non-immune AEs, increased aspartate aminotransferase (RR = 1.91; 95 CI, 1.11-3.28) and cough (RR = 1.32; 95CI, 1.11-1.57) had the highest RRs in favor of ICIs, respectively. The frequencies of overall any-grade and grade 3-5 irAEs were higher in the ICI group. Conclusion: The results showed that all the AEs and irAEs of all the categories were more prevalent with ICIs.