Using Trastuzumab Deruxtecan to treat advanced metastatic breast cancer in patients with varying HER2 expression levels: A single-center experience in Taiwan

To observe the clinical outcomes of patients diagnosed with metastatic breast cancer undergoing Trastuzumab Deruxtecan (T-DXd) therapy in a real-world setting. The study retrospectively reviewed and collected medical data from 13 patients at Shin Kong Wu Ho-Su Memorial Hospital who underwent T-DXd treatment over a period from April 2022 to June 2023. Demographics, pathological characteristics, treatment patterns, and outcomes were descriptively analyzed. Thirteen patients diagnosed with metastatic breast cancer underwent T-DXd treatment between April 2022 and June 2023. This study observed that T-DXd was effective in patients with high human epidermal growth factor receptor 2 (HER2) levels. In patients with low HER2, the majority also experienced favorable responses. Only 2 patients exhibited poor or no response: one was a BRCA2 carrier with unmanageable disease progression, and the other had a HER2 1 + status with multiorgan metastases whose cancer was not controlled by T-DXd. Additionally, 2 patients with no HER2 expression responded well to T-DXd treatment. T-DXd is a valuable treatment alternative for patients with breast cancer, including those with HER2-high, HER2-low, and HER2-negative statuses. In this study, the majority of patients experienced positive therapeutic effects. However, this evaluation relied on a limited sample size and short-term observations. Additional studies involving larger and more diverse patient groups and long follow-up durations are required.