Data extraction
Data extraction was conducted independently by two investigators (WXQ and JYC), and any discrepancy between the reviewers was resolved by consensus. For each study, the following information was extracted: study name, treatment setting, anti-HER2 regimen and dosage, duration of anti-HER2 therapy, concomitant therapy, No. of LVEF decline, No. of CHF and No. of patients for safety analysis.