Addressing HER2-Positive Residual Breast Cancer

It has long been recognized that among patients with HER2-positive breast cancer receiving neoadjuvant HER2 -directed therapy, those with residual disease at the time of surgery have a worse prognosis than those with a pathologic complete response. Investigators from the open-label, randomized, phase 3 KATHERINE trial previously reported that patients with residual disease after taxane-based HER2-directed neoadjuvant therapy had a 50% reduction in the risk for invasive breast cancer or death at 3 years with adjuvant trastuzumab emtansine (T-DM1) versus adjuvant trastuzumab alone. Now, with a median follow-up of 8.4 years, the investigators report that the benefit is sustained.

Seven-year invasive disease-free survival was 80.8% with T-DM1 versus 67.1% with trastuzumab, an absolute improvement of 13.7%. Additionally, T-DM1 was associated with a 34% relative reduction in death compared with trastuzumab; 7-year overall survival was 89.1% with T-DM1 versus 84.4% with trastuzumab. No new safety concerns were identified.