Nakajima H, Harano K, Nakai T, et al. - In tumors with heterogeneous, reduced, or loss of HER2 expression, the previous second-line treatment for HER2-positive metastatic breast cancer, ado-trastuzumab emtansine (T-DM1), shows reduced activity. Researchers herein investigated the ability of trastuzumab deruxtecan (T-DXd), a recently developed novel antibody-drug conjugate, to overcome resistance to T-DM1.

• Researchers enrolled 22 patients with HER2-positive metastatic breast cancer who received T-DXd.

• Favorable clinical activity was demonstrated by T-DXd against HER2-positive metastatic breast cancer.

• Patients with heterogeneity, reduction, or loss of HER2 expression benefited in correlation with receiving T-DXd.

• Tendency to experience worse outcomes was recorded for patients with liver metastasis.