Real-world patterns of endocrine therapy for metastatic hormone-receptor-positive (HR+)/human epidermal growth factor receptor-2-negative (HER2-) breast cancer patients in the United States: 2002-2012.

Objective: Clinical guidelines recommend that patients with HR+/HER2- metastatic breast cancer (mBC), the most prevalent mBC subtype, receive three lines of endocrine therapy (ET) prior to transitioning to chemotherapy (CT) in the absence of need for rapid response, symptomatic visceral disease, or suspected endocrine resistance. Little is known about real-world ET treatment patterns among HR+/HER2- mBC patients.

Research Design And Methods: Post-menopausal women with HR+/HER2- mBC were identified in the MarketScan databases (2002Q3-2012Q2). Patients were classified as receiving either ET or CT as their first therapy post-mBC diagnosis. Those receiving ET were studied further and stratified into three subgroups based on which of the following events occurred first: transition to CT, discontinuation of ET (90 days without evidence of ET), or end of data or insurance eligibility.

Main Outcome Measures: Mean numbers of lines of ET and median durations of each line were summarized for the overall sample and subgroups.

Results: Among a total of 19,120 HR+/HER2- mBC patients, 11,545 (60%) initiated an ET; median follow-up time for these patients was 17 months. Seventy-four percent did not receive a second ET. The average patient received 1.36 lines of ET. Among patients with 2+ lines of ET, the duration of each subsequent line was significantly shorter than the previous line. RESULTS were similar in all subgroups.

Limitations: Clinical characteristics and reasons for treatment choices are unavailable in claims data.

Conclusions: Fewer than two thirds of patients initiated treatment for HR+/HER2- mBC with ET. Among those who did, most received only one line of ET before discontinuation or transition to CT. Patients who received multiple lines of ET experienced shorter durations of therapy with each line. Real-world treatment with ET falls short of the targets recommended by guidelines, representing unmet need for treatment options that improve the effectiveness of endocrine therapy.