Dr. Gralow Discusses T-DM1-Induced Thrombocytopenia

Julie R. Gralow, MD, Director, Breast Medical Oncology, Seattle Cancer Care Alliance (SCCA), discusses a group of clinical trials, currently being conducted by SCCA, that are investigating the agent T-DM1 (trastuzumab emtansine) for patients with HER2-positive metastatic breast cancer, following the administration of two prior HER2-targeted therapies.

The most prominent side effect associated with T-DM1 treatment is thrombocytopenia. The occurrence and severity of this side effect generally depends on the dose and duration of treatment. In many cases, the platelet count for patients receiving T-DM1 for a longer duration will drop to between 50,000 and 75,000 platelets per microliter of blood.

To date, Gralow adds, the cause of the T-DM1-induced thrombocytopenia is widely unknown. In order to discover the best way to manage this side effect, the SCCA is beginning a trial in conjunction with their blood bank that will use pheresis to monitor the effects of T-DM1 on platelet counts.