In the article by Portera et al., beginning on page 2710 of the May 1 issue, the title should be Cardiac Toxicity and Efficacy of Trastuzumab Combined with Pertuzumab in Patients with Human Epidermal Growth Factor Receptor 2-Positive Metastatic Breast Cancer. The word “domain” is mistakenly repeated in the first full paragraph of page 2711. On page 2712, under “statistical considerations” the sentence should read: The planned sample size was 37 based on Simon two-stage optimal design to target a 20% response rate and rule out an unacceptably low 5% response rate (P = 0.05; ref; 31). In Table 4, the median value (range) for pHER2-Y1248 is 56.0 (54.3–57.7).