"Cardiac safety is important to look at whenever you’re talking about HER-2 targeting agent," said Dr. Hurvitz.
Adjuvant anthracyclines were given to 45% and 49% of patients in the T-DM1 arm and control arm. On local assessment two patients in the control arm, compared with none in the T-DM1 arm, had a postbaseline left ventricular ejection fraction of 40% or less.
"There were no clinically significant cardiac events reported," she noted.
Dr. Hurvitz and Dr. Piccart-Gebhart agreed that large phase III trials are needed to confirm these findings. The drug is being evaluated in three large phase III clinical trials for HER2-postive metastatic breast cancer.
The study was funded by F. Hoffmann-La Roche. Dr. Hurvitz reported that she has no relevant financial disclosures. Dr. Piccart-Gebhart has previously reported that she is a consultant for and has received research support from several pharmaceutical companies, including Roche.
* Clarification, 9/29/2011: The original version of this article stated that trastuzumab emtansine improved disease-free progression. However, it is more accurate to say that it improved progression-free survival. This version has been updated.