Adjuvant treatment with trastuzumab emtansine (T-DM1) showed an “excellent” 3-year invasive disease-free survival (iDFS) among patients with stage I human epidermal growth factor receptor 2-positive (HER2+) breast cancer, but was not associated with fewer clinically relevant toxicities when compared with paclitaxel plus trastuzumab (TH), according to research published in the Journal of Clinical Oncology.

Although trastuzumab-based therapy is the standard treatment for early-stage, HER2+ breast cancer, retrospective data collected from this population suggest that these patients are at a sufficiently high risk for recurrence to warrant systemic therapy. Previous results from the APT trial ( Identifier: NCT00542451) showed favorable outcomes with adjuvant TH treatment in patients with HER2+ breast cancer, the study authors stated.

In the randomized, phase 2 ATEMPT trial ( Identifier: NCT01853748), researchers compared the efficacy and safety of adjuvant T-DM1 for 1 year with that of TH in patients with stage I HER2+ breast cancer. The analysis population included 497 patients who were randomly assigned in a 3:1 ratio to receive either T-DM1 (383 patients) or TH (114 patients). The median follow-up of the study was 3.9 years.

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The 3-year iDFS for the T-DM1 arm was 97.8% (95% CI, 96.3-99.3; P <.0001). While this study was not powered to evaluate the efficacy of TH with just 114 patients in this arm, the 3-year iDFS for patients receiving TH was 93.4% (95% CI, 88.7-98.2), and the 3-year recurrence-free interval was 94.3% (95% CI, 89.9-98.8).

There was statistically no significant difference in the rate of clinically relevant toxicities between the T-DM1 (46%) and TH (47%) treatment arms (P =.83). However, the 2 treatment arms exhibited different adverse event (AE) profiles. According to the patient-reported outcomes surveys, patients treated with T-DM1 had less hair loss and neuropathy and better work productivity compared with patients treated with TH. Conversely, thrombocytopenia, elevated bilirubin, and treatment discontinuation were more common in the T-DM1 group compared with the TH group. 

“Given the low event rate and improved quality of life associated with T-DM1 in this study, T-DM1 may be considered an alternative treatment to TH for patients with stage I [HER2+] disease,” the authors commented. “T-DM1 may be an ideal choice for patients who are concerned about specific TH-related side effects, such as neuropathy and alopecia, and who understand the potential for T-DM1 [AEs] such as elevated bilirubin and thrombocytopenia,” they added.

Disclosure: This research was supported by Genentech and the Gloria Spivak Faculty Advancement Fund (Tolaney). Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Tolaney SM, Tayob N, Dang C, et al. Adjuvant trastuzumab emtansine versus paclitaxel in combination with trastuzumab for stage I HER2-positive breast cancer (ATEMPT): a randomized clinical trial. J Clin Oncol. Published online June 02, 2021. doi:10.1200/JCO.20.03398