Trastuzumab emtansine targets residual invasive HER2-positive breast cancer
medwireNews: Adjuvant trastuzumab emtansine (T-DM1) halves the risk of invasive disease recurrence or death versus trastuzumab in patients with residual invasive human epidermal growth factor receptor (HER)2-positive early breast cancer, researchers report.
The preliminary findings of the KATHERINE trial, at around 41 months of follow-up, showed that 91 (12.2%) of 743 patients randomly assigned to receive adjuvant T-DM1 3.6 mg/kg every 3 weeks for 14 cycles had a recurrence of invasive disease or died during the study.
This was significantly lower than the 165 (22.2%) cases of recurrent invasive disease or death observed among the 743 patients randomly assigned to receive adjuvant trastuzumab 6.0 mg/kg on the same schedule , Gunter von Minckwitz (German Breast Group, Neu-Isenburg) and colleagues report in The New England Journal of Medicine.
All of the women included in the phase III study had HER2-positive early breast cancer with residual invasive disease in the breast or axilla detected at surgery after completion of neoadjuvant therapy containing a taxane (with or without anthracycline) and trastuzumab.
The estimated 3-year invasive disease-free survival rate – defined as freedom from ipsilateral invasive breast tumour recurrence, ipsilateral locoregional invasive breast cancer recurrence, contralateral invasive breast cancer, distant recurrence or death – was 88.3% in the T-DM1 group and 77.0% in the trastuzumab group.
This corresponded to a statistically significant hazard ratio of 0.50, in favour of T-DM1.
von Minckwitz and team also found that women who received T-DM1 had a lower rate of distant recurrence as the first invasive-disease event than those who received trastuzumab, at 10.5% versus 15.9%.
Furthermore, similar results were observed across a number of subgroup analyses that stratified women by baseline characteristics, hormone receptor status, extent of residual disease after surgery and whether they received single or dual HER2-targeted therapy in the neoadjuvant regimen.
The investigators say that “[t]he safety profile of T-DM1 was consistent with that in previous studies; as expected, there were more adverse events with T-DM1 than with adjuvant trastuzumab.”
Indeed, the serious adverse event rate was 12.7% with T-DM1 and 8.1% with trastuzumab, while 18.0% and 2.1% of patients receiving T-DM1 and trastuzumab, respectively, discontinued treatment as a result of adverse events.
von Minckwitz and co-authors conclude: “Additional follow-up will be necessary to determine whether there is an effect of adjuvant T-DM1 on overall survival.”
These results were simultaneously presented at the 2018 San Antonio Breast Cancer Symposium in Texas, USA.
By Laura Cowen
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