Papakonstantinou A, Matikas A, Bengtsson NO, et al. - Given that improved outcomes in early breast cancer (BC) are afforded by dose-dense (DD) adjuvant chemotherapy, but there exists no phase 3 randomized data to inform about its combination with trastuzumab for patients suffering from human epidermal growth factor receptor 2 (HER2)–positive disease, and therefore, researchers undertook this protocol-predefined secondary analysis of the randomized phase 3 Pan-European Tailored Chemotherapy (PANTHER) trial. Participants were women 65 years old or younger with node-positive or high-risk, node-negative BC. The participants were randomly assigned 1:1 to either tailored (according to hematologic nadirs) and DD epirubicin and cyclophosphamide followed by docetaxel or standard 5-fluorouracil, epirubicin, and cyclophosphamide plus docetaxel every 3 weeks. One year of adjuvant trastuzumab was given to patients with HER2-positive disease. BC relapse–free survival was the primary endpoint. Relative to the standard treatment, a reduction in the relative risk for relapse by 32% was afforded by the combination of DD chemotherapy and trastuzumab, a statistically nonsignificant difference. As far as its efficacy and safety are concerned, these merit further assessment as part of both escalation and de-escalation strategies. No significant difference was evident in cardiac outcomes following 4 and 6 years of follow-up between HER2-positive and HER2-negative patients or between the 2 treatment groups.