Obese breast cancer patients on T-DM1 prone to more treatment adjustments

More treatment modifications secondary to adverse events appear necessary among obese patients receiving ado-trastuzumab emtansine (T-DM1), an antibody-drug conjugate indicated for the treatment of HER2-positive breast cancer, relative to nonobese counterparts, reports a study.

A total of 119 patients with HER2-positive breast cancer who received T-DM1 therapy were included in this retrospective chart review. The primary endpoint was a composite of the incidence of T-DM1 treatment modifications secondary to an adverse event, while secondary ones included the incidence of dose reductions, dose delays, treatment discontinuations, and adverse events.

Of the patients, 44 were obese and 75 nonobese. Obese patients had significantly more treatment modifications due to toxicity than nonobese individuals (45 percent vs 25 percent; p=0.024). Treatment delays were also significantly greater in the obese group (36 percent vs 16 percent; p=0.011).

All-grade adverse events with a higher incidence in obese patients were as follows: left ventricular ejection fraction decrease (11 percent vs 5 percent), bilirubin increase (32 percent vs 12 percent), thrombocytopaenia (61 percent vs 55 percent), and peripheral neuropathy (34 percent vs 27 percent).

“Larger studies are needed to determine if obese patients are at higher risk for specific T-DM1-induced adverse events,” the investigators said.

Based on the 2012 American Society of Clinical Oncology guidelines on chemotherapy dosing in obesity, full weight-based cytotoxic chemotherapy doses are recommended to treat obese patients with cancer. Of note, such guidelines were established before the advent of anticancer antibody-drug conjugates, according to the investigators.