SABCS 2019 – HER2+ breast cancer: trastuzumab emtansine fails to top paclitaxel plus trastuzumab


  • Ben Gallarda
  • Univadis
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Takeaway

  • Adjuvant trastuzumab emtansine (T-DM1) failed to demonstrate a DFS or safety advantage over paclitaxel plus trastuzumab (TH) for patients with stage I human epidermal growth factor receptor 2(HER2)-positive breast cancer.

Why this matters

  • The drug antibody conjugate, T-DM1 has activity against metastatic HER2-positive breast cancer and in patients with residual disease after neoadjuvant HER2-directed therapy.

Study design

  • Multicenter, phase 2 ATEMPT study.
  • 497 patients with HER2-positive breast cancer were randomly assigned (3:1) to either T-DM1 every 3 weeks for 17 cycles or TH weekly for 12 cycles followed by trastuzumab every 3 weeks for further 13 cycles.
  • Primary endpoints were 3-year DFS or clinically relevant toxicities (CRTs).
  • Funding: Genentech, Inc.

Key results

  • 3-year DFS rates for the T-DM1 and TH groups were 97.5% and 93.2%, respectively.
  • CRTs were observed in 46% of patients in each group.
  • Grade 3 or higher nonhematologic toxicities in the T-DM1 and TH groups were 10% and 11%, respectively, and grade ≥2 neurotoxicities were 11% and 23%, respectively.
  • 4 patients in the T-DM1 group had grade 4 hematologic toxicity vs none in the TH group.
  • 17% of patients in the T-DM1 group had toxicities requiring early discontinuation vs 6% in the TH group.

Limitations

  • Study was not powered to determine efficacy differences between groups.
  • Short median follow-up duration.

Expert commentary

  • Responding to an audience member's concerns regarding the financial toxicity of T-DM1, Dr. Sara. M. Tolaney, MD, MPH of Dana-Farber Cancer Institute, Boston, said “certainly we did consider this and we had our pharmacist do some calculations looking at this financial toxicity, and it is true that a year of T-DM1 does cost a little more than two times as much as TH.”