Adjuvant trastuzumab emtansine reduces HER2-positive breast cancer recurrence risk
medwireNews: Among patients with early-stage HER2-positive breast cancer who have residual disease after neoadjuvant therapy and surgery, the use of trastuzumab emtansine instead of trastuzumab leads to significant improvements in invasive disease-free survival, indicate KATHERINE trial findings.
In the phase III trial of patients with residual invasive disease in the breast or axilla following neoadjuvant taxane-based chemotherapy (with or without anthracycline) plus trastuzumab, the risk for invasive breast cancer or death was halved for the 743 participants who were randomly allocated to receive trastuzumab emtansine 3.6 mg/kg every 3 weeks for 14 cycles after surgery than for their 743 counterparts who received trastuzumab 6.0 mg/kg on the same schedule.
As reported in The New England Journal of Medicine and at the 2018 San Antonio Breast Cancer Symposium in Texas, USA, the estimated 3-year invasive disease-free survival rates were 88.3% for the trastuzumab emtansine arm and 77.0% for the trastuzumab arm.
Treatment with the antibody–drug conjugate trastuzumab emtansine also resulted in a significant 40% reduced risk for distant recurrence relative to trastuzumab, and the proportion of patients experiencing distant recurrence as the first invasive disease event was 10.5% and 15.9%, respectively.
Gunter von Minckwitz, from the German Breast Group in Neu-Isenburg, and co-investigators note that the invasive disease-free survival benefit associated with trastuzumab emtansine was consistent across subgroups and was observed “irrespective of hormone-receptor status, the extent of residual disease at surgery, single or dual HER2-targeted therapy in the neoadjuvant regimen, and baseline characteristics of the patients.”
The overall survival data were not mature at data cutoff, at a median of 41.4 and 40.9 months in the trastuzumab emtansine and trastuzumab groups, respectively, and the study authors say that “[a]dditional follow-up will be necessary to determine whether there is an effect of adjuvant [trastuzumab emtansine] on overall survival.”
They add that the adverse event (AE) data from KATHERINE “were consistent with the known safety profile” of the antibody–drug conjugate, “with more adverse events associated with [trastuzumab emtansine] than with trastuzumab alone.”
Grade 3 or more severe AEs occurred in 25.7% of trastuzumab emtansine-treated patients compared with 15.4% of those given trastuzumab, and the incidence of serious AEs was also higher with trastuzumab emtansine, at 12.7% versus 8.1%, as was the rate of discontinuation due to AEs, at 18.0% versus 2.1%.
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