Real-world Outcomes of Patients With HER2+ Metastatic Breast Cancer After Treatment With Trastuzumab Deruxtecan

This study will explore treatment patterns and clinical outcomes using the US-based Flatiron Health database to describe patients with HER2+ mBC who were previously treated with T-DXd to better characterize this population and inform internal decision making in this rapidly changing therapeutic landscape.

This study will utilize a longitudinal, demographically and geographically diverse database derived from Electronic Health Record data. No study medication will be supplied or administered for this protocol. The primary research objective is to describe the real-world progression-free survival (rwPFS) in HER2+ mBC patients who initiated a subsequent line of therapy (LOT) after a T-DXd-containing LOT in the metastatic setting. Secondary research objectives include describing the real-world overall survival (rwOS), patient demographics and clinical characteristics, real-world time to next treatment (rwTTNT), and real-world time to treatment discontinuation (rwTTD) in HER2+ mBC patients who initiated a subsequent LOT after a T-DXd-containing LOT in the metastatic setting. Treatment patterns and sequencing in HER2+ mBC patients for subsequent LOTs following initial treatment with T-DXd will also be assessed.