Chemotherapy outcomes in human epidermal growth factor receptor 2-low, hormone receptor-positive metastatic breast cancer: Insights from the French multicenter ESME database.

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.