Patients with HER2-positive early breast cancer and residual invasive disease after neoadjuvant systemic therapy are at high risk for recurrence and death. Prior results of the open-label phase III KATHERINE trial at a median follow-up of 41 months demonstrated that adjuvant trastuzumab emtansine (T-DM1) reduced the risk of recurrence of invasive breast cancer or death by 50% compared to trastuzumab.1 Longer follow-up data of this trial were recently published.2
METHODS
The KATHERINE trial randomised 1,486 HER2-positive early breast cancer patients with residual invasive disease following neoadjuvant treatment with taxane-based chemotherapy (with or without anthracycline) and trastuzumab (with or without pertuzumab) to treatment with T-DM1 or trastuzumab. This article presents the prespecified final analysis of invasive disease-free survival (iDFS) and the second interim analysis of overall survival (OS).
RESULTS
At a median follow-up of 8.4 years, T-DM1 maintained its advantage in iDFS over trastuzumab (HR[95% CI]: 0.54[0.44-0.66]). The 7-year iDFS rate was 80.8% for T-DM1 compared to 67.1% for trastuzumab, a difference of 13.7 percentage points. T-DM1 also significantly reduced the risk of death compared to trastuzumab (HR[95% CI]: 0.66[0.51-0.87], p= 0.003). Seven-year OS was 89.1% in the T-DM1 group vs 84.4% in the trastuzumab group, a difference of 4.7 percentage points. Grade ≥3 adverse events occurred in 26.1% of patients in the T-DM1 group and 15.7% in the trastuzumab group.
CONCLUSIONS
Compared to trastuzumab, T-DM1 significantly improved OS and sustained its benefit in iDFS in patients with HER2-positive early breast cancer having residual invasive disease after neoadjuvant therapy.
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