[Successful Ninth-Line Therapy with Trastuzumab Deruxtecan in Recurrent Breast Cancer with Low HER2 Expression-A Case...

Trastuzumab deruxtecan(T-DXd)is approved as a second-line treatment for HER2-positive advanced or recurrent breast cancer. Recently, its indication has been expanded to include advanced or recurrent breast cancer exhibiting low HER2 expression and a history of prior chemotherapy. Approximately 45-55% of all breast cancers fall into the HER2-low category, highlighting T-DXd as a promising therapeutic option in the subset. The DESTINY-Breast04 trial demonstrated the efficacy of T-DXd in patients with HER2-low metastatic breast cancer patients who had received one or two prior lines of chemotherapy for advanced or recurrent disease. Here, we present a case of recurrent breast cancer with low HER2 expression in which T-DXd was effective as a ninth-line treatment.