Clinical Outcomes with First-line Endocrine Therapy or Chemotherapy in Postmenopausal HR+/HER2- Metastatic Breast Cancer

Objective: To describe patient profiles and clinical outcomes associated with first-line endocrine monotherapy (ET) and chemotherapy (CT) for postmenopausal HR+/HER2- metastatic breast cancer (mBC) patients.

Methods: This is a retrospective chart review of 139 postmenopausal HR+/HER2- mBC patients initiating first-line ET monotherapy or CT. Overall survival (OS) was described using Kaplan-Meier curves. Exploratory comparative proportional hazards regression was conducted.

Results: Patients on first-line CT had significantly more frequent liver metastases than patients on first-line ET monotherapy at baseline. The median OS was 35.5 months [95% confidence interval (CI), 22.7-41.2 months] for patients on first-line ET monotherapy and 22.2 months (95% CI, 13.6-25.9 months) for those on first-line CT (P = 0.021). Adjusting for baseline characteristics, the OS between first-line ET monotherapy and CT was not significantly different.

Conclusions: Patients who were prescribed CT as first-line treatment had evidence of more advanced disease at baseline and shorter OS than those who received ET monotherapy as first-line treatment, suggesting a need for additional safe and effective treatment options for these patients.