T-DM1 was associated with higher rates of grade 3 or worse thrombocytopenia (12.9% vs. 0.2%) and elevations of aspartate aminotransferase (4.3% vs. 0.8%) and alanine aminotransferase (2.9% vs. 1.4%); notably, however, cardiac toxicity (an adverse effect seen with trastuzumab) was not elevated with T-DM1. On the other hand, capecitabine-lapatinib was associated with higher rates of diarrhea (20.7% vs. 1.6%), hand-foot syndrome (16.4% vs. 0%), and vomiting (4.5% vs. 0.8%).
Patients given capecitabine-lapatinib were significantly more likely to discontinue treatment because of toxicity, according to Dr. Blackwell.
"We would hope that these data would support the availability of the drug for patients faced with HER2-positive breast cancer," she concluded.
Dr. Blackwell disclosed no relevant conflicts of interest. The trial was sponsored by Genentech, manufacturer of T-DM1. Dr. Seidman disclosed that he is a consultant to Enzon and Wyeth, and receives honoraria from Celgene, Genentech, and Genomic Health. Dr. Weiner disclosed that he is a consultant to Abbott Laboratories, Celldex, Johnson and Johnson, Merrimack, Samsung Advanced Institute of Technology, and Symphogen; owns stock in Celldex and Merrimack; receives honoraria from Bristol-Myers Squibb; and receives research funding from Samsung Advanced Institute of Technology.
*This article was updated June 4, 2012.