Trastuzumab Deruxtecan for Breast Cancer.

To the Editor: In the DESTINY-Breast03 trial, Cortes et al. (Mar. 24 issue)(1) found that trastuzumab deruxtecan therapy prolonged progression-free survival to a greater extent than trastuzumab emtansine therapy among patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer previously treated with trastuzumab and a taxane. The percentage of patients with an overall response (complete or partial response) increased from 60.9% in an earlier, phase 2, single-group study(2) to 79.7% in the phase 3 trial. Furthermore, in the trial, 58.2% of the patients in the trastuzumab deruxtecan group were Asian and 27.2% were White; in the trastuzumab . . .