After surgery, they received combination chemotherapy and then more of the same HER2 therapy out to 52 weeks, as well as hormonal therapy if indicated.
Initial results, previously reported, showed that the rate of pCR – the trial’s primary endpoint – was 24.7% with lapatinib alone, 29.5% with trastuzumab alone, and 51.3% with the combination, Dr. Piccart-Gebhart reported.
The new results showed that there were no significant differences between the treatment arms in the adjusted 3-year rates of event-free survival (78%, 76%, and 84%, respectively) or overall survival (93%, 90%, and 95%, respectively). But there was greater separation of the curves in the hormone receptor–negative subset, suggesting a possible treatment effect, according to Dr. Piccart-Gebhart.
In an analysis of all trial arms combined that used a starting point of 30 weeks after randomization, relative to patients who did not have a pCR, those who did were significantly less likely to have events (postoperative recurrence, second primary, or death, or progression in those who did not have surgery) (hazard ratio, 0.38; P = .0003) and to die (HR, 0.35; P = .005).
"There were no surprises" in terms of adverse events, she reported. "The adverse events were consistent with the known safety profiles of lapatinib and trastuzumab."
Over the entire study period, compared with trastuzumab alone, the combination of lapatinib plus trastuzumab led to higher rates of severe diarrhea, hepatobiliary adverse events, and rash, as well as a higher rate of cardiac events.
Dr. Piccart-Gebhart disclosed that she has received consulting fees from Roche, and her institution has received research funding from GlaxoSmithKline PLC and Roche. The trial was sponsored by GlaxoSmithKline.