Yu YF, et al. - Researchers herein used data from randomized clinical trials (RCTs) to determine the efficacy and safety of doublet vs single-agent chemotherapy (CT) plus trastuzumab (H) as first-line therapy for human epidermal growth factor 2 receptor (HER2)-positive metastatic breast cancer (MBC). They noted longer progression-free survival and overall survival but more treatment-related grade 3 or 4 toxicities in relation to treatment with doublet vs single-agent CT plus trastuzumab as first-line therapy for HER2-positive MBC. Therefore, doublet CT appeared to be an appropriate regimen for HER2-positive MBC with a good performance status.