Improved survival supports primary endocrine therapy in patients with hormone receptor positive/ HER-2 negative metastatic breast cancer.

Abstract

e13034 Background: Current ASCO guidelines recommend endocrine therapy as preferred primary treatment for hormone receptor positive (HR+) metastatic breast cancer (MBC). We assessed survival outcomes of HR+/HER2- MBC patients undergoing endocrine therapy with and without chemotherapy. Methods: The National Cancer Database was queried 2004-2016 for patients with de novo HR+/HER2- MBC. Exclusion criteria were treatment with surgery or radiation at the primary site and missing oncologic and follow up data. Overall survival was compared between systemic treatment groups using multivariable cox proportional hazards regression modes. Results: 19,317 patients met inclusion criteria, among whom 2,360 (12%) received no systemic therapy, 2,617 (14%) received chemotherapy only, 10,078 (52%) received endocrine therapy only and 4,262 (22%) received both chemotherapy and endocrine therapy. Patients treated with chemotherapy only more frequently had lung (38%, p<0.001) or liver (36%, p<0.001) metastasis while those undergoing endocrine therapy only presented primarily with bone metastasis (82%, p<0.001). Patients with multiple metastatic sites more often received endocrine therapy alone than combined therapy (44 vs. 25%, p<0.001). Median overall survival was similar after combination therapy and endocrine therapy, and poorest after chemotherapy alone (33.1 vs 31.4 vs 19.8 months, p<0.001). After controlling for patient, facility, and tumor characteristics, endocrine therapy alone provided superior survival benefit to chemotherapy only, though combination systemic therapy resulted in the greatest overall survival (p<0.001). Conclusions: Primary endocrine therapy provided significant survival benefit over chemotherapy alone for HR+/HER2- MBC. Though combination systemic therapy may be warranted in progressive disease, our results align with recommendations for endocrine therapy as first line treatment for HR+/HER2- MBC. [Table: see text]