BACKGROUND:The human epidermal growth factor receptor 2 (HER2)-targeted therapy trastuzumab deruxtecan has demonstrated significantly improved efficacy versus chemotherapy in HER2-low or -ultralow, hormone receptor (HR)-positive metastatic breast cancer (mBC) following endocrine therapy (ET). This study describes current real-world characteristics and outcomes for this population in France to inform optimized treatment sequencing, including the potential benefits of novel treatments.
METHODS:Data were obtained from the Unicancer Epidemiological Strategy and Medical Economics (ESME) MBC database of adult patients with mBC. Patients were diagnosed with HER2-low, HR-positive mBC between 2008 and 2022 and initiated a chemotherapy-based regimen (index line of therapy [LOT]) after ≥1 qualifying line of ET. Real-world overall survival (rwOS) and progression-free survival (rwPFS) were assessed from the start of index LOT.
RESULTS:Among 326 patients selected, index LOT was third line (3L) or greater ("index 3L+ group") for 202 (62.0%) patients and second line for 124 (38.0%) patients; 101 (31.0%) patients initiated index LOT after progression within 6 months of first-line ET + cyclin-dependent kinase 4/6 inhibitor ("rapid progressors"). Median rwOS (95% confidence interval [CI]) for the overall cohort, index 3L+ group, and rapid progressors was 23.1 (19.7, 27.5), 27.6 (22.7, 31.3), and 18.6 (14.3, 23.0) months, respectively. Median rwPFS (95% CI) for the overall cohort, index 3L+ group, and rapid progressors was 5.1 (4.8, 5.7), 5.2 (4.7, 6.0), and 5.6 (4.6, 6.3) months, respectively.
CONCLUSIONS:These real-world data suggest limited long-term efficacy of chemotherapy-based treatments for patients with ET-resistant HER2-low, HR-positive mBC, emphasizing high unmet need in this population.