Trastuzumab Emtansine Improved Long-Term Outcomes Among Patients With HER2-Positive Early Breast Cancer

5-Year Results from the ATEMPT Trial 

According to 5-year results from the phase 2 ATEMPT trial, adjuvant trastuzumab emtansine improved long-term outcomes among patients with human epidermal growth factor receptor 2 (HER2)-positive early-stage invasive breast cancer. 

According to Paolo Tarantino, MD, Dana-Farber Cancer Institute, Boston, Massachusetts, and coauthors, “long-term outcomes of patients with stage I human epidermal growth factor receptor 2 (HER2)-positive breast cancer receiving trastuzumab emtansine (T-DM1) remain undefined, and prognostic predictors represent an unmet need.” 

In this multicenter, investigator-initiated study, 497 patients with pathologic stage I HER2-positive invasive breast cancer were randomized on a 3-to-1 basis to receive either adjuvant trastuzumab emtansine (n = 383) or paclitaxel plus trastuzumab (n = 114) for a duration of 1 year. Patients treated with trastuzumab emtansine were followed after completion of study treatment for primary end points of invasive disease-free survival (iDFS), recurrence-free interval (RFI), overall survival (OS), and breast-cancer specific survival. The HER2DX genomic tool was used to perform correlative analyses among patients with sufficient tissue (n = 187). 

After a median follow-up of 5.8 years, 11 iDFS events were observed and iDFS rate was 97%. The RFI was 98.3%, OS was 97.8%, and breast-cancer specific survival was 99.4%. Although the study was not powered to evaluate the efficacy of paclitaxel plus trastuzumab, there were 9 iDFS events observed in this arm, and iDFS rate was 91.1%. The RFI was 93.2%, OS was 97.9%, and breast-cancer specific survival was 99% in the paclitaxel plus trastuzumab arm. Among patients with sufficient tissue for evaluation with the HER2DX genomic tool, the RFI was 98.1% for HER2DX low-risk patients and 81.8% for HER2DX high-risk patients (P = .01). The iDFS was 96.3% for HER2DX low-risk patients and 81.8% for HER2DX high-risk patients (P = .047). 

“This final analysis of ATEMPT confirms the outstanding efficacy of T-DM1 at preventing recurrences of stage I HER2-positive breast cancer,” concluded Dr Tarantino et al.  

According to Journal of Clinical Oncology Editor-in-Chief Jonathan Friedberg, MD, University of Rochester Medical Center, Rochester, New York, “Adjuvant T-DM1 is a treatment option for patients with stage I HER2 positive breast cancer who are not candidates of chemotherapy, resulting in durable responses.” 

Source: 

Tarantino P, Tayob N, Villacampa G, et al. Adjuvant trastuzumab emtansine versus paclitaxel plus trastuzumab for stage I human epidermal growth factor receptor 2–positive breast cancer: 5-Year results and correlative analyses from ATEMPT. J Clin Oncol. Published online: June 27, 2024. doi: 10.1200/JCO.23.02170