How I treat HER2-positive early breast cancer: how long adjuvant trastuzumab is needed?

Since its first approval in 2006, 1 year of adjuvant trastuzumab has been the standard of care for early-stage HER2-positive breast cancer. Nevertheless, the optimal duration of adjuvant trastuzumab was uncertain, and the standard 12-month duration has been questioned by a number of different trials. Although most of these studies were formally negative, a patient-level meta-analysis presented at the 2021 European Society for Medical Oncology (ESMO) meeting first showed the non-inferiority of 6-month trastuzumab. Through this review, we sought to take a closer look at the meta-analysis and the included trials to explain why we believe that non-inferiority should be interpreted with caution. Indeed, here we underline how the meta-analysis' results were mainly driven by the PERSEPHONE study, an old trial that tested non-standard chemo-trastuzumab regimens in a relatively low-risk population with doubtful endpoints. In summary, considering all the limitations of this analysis and the increasing use of effective anthracycline-free de-escalation strategies, we are convinced that 1-year trastuzumab should remain the standard of care.