Background: Endocrine therapy (ET) remains a foundation of systemic therapy for HR+/ HER2- metastatic breast cancer (MBC), although chemotherapy (CT) is used in select patients. In this "real-world" study, we explored treatment patterns, health care resource use (HCRU), costs, adverse events (AEs) and overall survival (OS) in Medicare-enrolled, older patients with HR+/HER2- MBC. Methods: Patients with HR+/HER2- MBC (2007-2011) and aged >66 years were retrospectively analyzed using the SEER-Medicare data. Treatment patterns, HCRU, costs, AEs and OS after MBC diagnosis through end of study period (31 December 2013) were examined using descriptive and multivariable analyses. Results: Among 3622 eligible patients, ET was the most common treatment (77%), followed by CT (50%), radiation (48%) and surgery (19%). The proportion of patients treated with ET monotherapy decreased across therapy lines, from 74% in first line (1 L) to 35% in 4 L. The total number of unique therapy regimens used was 181 in 1 L, 171 in 2 L, 128 in 3 L, and 95 in 4 L. The median OS from MBC diagnosis was 25.3 months (95% CI, 24.0-26.7). In multivariable analyses, receipt of CT and combination CT + ET (versus ET monotherapy) in 1 L, metastatic disease at initial diagnosis, larger tumor size, and presence of visceral and brain metastases at MBC diagnosis significantly predicted receipt of 2 L therapy. Conclusions: ET was the most common first-line treatment for study patients, but its use decreased gradually in the subsequent lines. The heterogeneity in the treatment selection highlights a lack of consensus for the management of HR+/HER2- MBC in routine practice.
Keywords: Metastatic breast cancer; adverse events; health care costs; health care use; survival; treatment patterns.