Two years of trastuzumab provide no benefit over the standard of 1 year of trastuzumab therapy for human epidermal growth factor receptor 2–positive (HER2+) breast cancer, according to an 8-year follow-up of the Herceptin Adjuvant (HERA) trial reported by Martine Piccart, MD, president of the European Society for Medical Oncology and chair of the Breast International Group, Institut Jules Bordet, Brussels, Belgium. “One year of trastuzumab should remain the standard of care,” she said.
HERA was a large international trial that accrued 5102 women with HER2+ breast cancer in a little more than 3 years. Oncologists had the choice of neoadjuvant or adjuvant therapy, and patients were randomized to receive 1 or 2 years of trastuzumab following chemotherapy.
For the primary end point of the trial, disease-free survival (DFS) was significantly better for 1 year versus observation. The secondary end point was DFS after 1 year versus 2 years of trastuzumab.
At 8 years, no difference in DFS was observed between the 2 arms, and both were significantly better than observation. At baseline, all patients had left ventricular ejection fraction of 55%; the cumulative incidence of cardiac end points showed no difference between the 2 arms. “Severe cardiac end points are rare,” Piccart said.
Most cardiac events occurred during the first year of treatment and then the curves of both arms reached a plateau. Few women experienced cardiac events after stopping trastuzumab, she said. “We were concerned that there would be a progressively smaller effect of 1 year of treatment with trastuzumab over time. Now with 8 years of follow-up, there is no further attenuation of benefit as was seen at 1 year, and a very robust effect with 1 year of trastuzumab.”
No difference was seen between hormone receptor–positive and hormone receptor–negative patients. No attenuation of overall survival benefit was seen at 8 years.