[Experience with Trastuzumab Deruxtecan for Brain Metastases of Breast Cancer].

Breast cancer is a representative malignancy that is prone to brain metastasis. Recently, several studies have reported the efficacy of trastuzumab deruxtecan(T-DXd)in treating brain metastases. We have used T-DXd in 10 patients with brain metastases, and stereotactic or whole brain irradiation was performed in 9 of 10 patients. All patients had symptoms of brain metastases. Because T-DXd was administered in the late line in the early cases, symptoms due to brain metastases or meningeal dissemination worsened during T-DXd administration in a few cases. None of the four most recent cases showed worsening of brain metastasis or symptoms due to brain metastasis after T-DXd use. We would like to accumulate more cases and investigate whether T-DXd can be preferred over irradiation for asymptomatic patients with brain metastases.