This study aims to evaluate whether the combination of Megestrol Acetate at the initiation of Trastuzumab Deruxtecan (T-DXd) treatment can effectively prevent and alleviate T-DXd-related fatigue, thereby improving the quality of life for advanced breast cancer patients.
Female, aged 18-75 years
Pathologically confirmed inoperable or metastatic breast cancer with complete ER, PR, and HER2 status
HER2-positive (IHC 3+ or IHC 2+ with FISH positive), HER2-low (IHC 1+ or IHC 2+ with FISH negative), or HER2-ultralow (IHC 0 with ≤10% weak incomplete membrane staining) [most recent specimen used]
Investigator-assessed indication for Trastuzumab Deruxtecan (T-DXd) therapy
Severe underlying disease, comorbidities, active infection, or severe metabolic disorders
Clinically significant severe fatigue at baseline (FACIT-F score <30)
Currently receiving other antitumor therapies
Pregnant or lactating patients