Abstract P1-13-08: Real-world treatment durations without chemotherapy (CT) for hormone-receptor-positive (HR+)/human epidermal growth factor receptor-2-negative (HER2-) metastatic breast cancer (mBC)

Background: Guidelines recommend maximizing the duration of effective treatment that can be achieved without chemotherapy for HR+/HER2- mBC, with the goal of avoiding toxicity and preserving quality of life. A target of three lines of ET is suggested, with CT reserved for patients requiring rapid control of symptomatic disease or who no longer benefit from ET. This study describes treatment patterns for HR+/HER2- mBC over the past decade. Methods: Postmenopausal women (age ≥50) with HR+/HER2- mBC were identified from the MarketScan® databases (2002Q3-2012Q2). Patients whose first treatment after mBC diagnosis included ET without CT were followed until first use of CT, discontinuation of ET (>90 days without evidence of ET), or end of data or insurance eligibility. The distribution of agents used prior to CT was assessed for up to 3 lines of therapy. Median treatment durations were calculated by agent and by line among patients who received at least 3 lines of treatment that included ET without CT. Results: Of 19,120 HR+/HER2- mBC patients, 11,545 (60%) initiated a 1st-line therapy for mBC that included ET without CT. The remaining 40% initiated with CT. Of the 11,545 patients who initiated ET, the majority received the non-steroidal aromatase inhibitors (NSAIs) anastrozole (38%) and letrozole (27%) in the 1st-line. Among these patients, 3,021 (26%) patients received 2nd-line ET without CT, with the majority receiving exemestane (20%), anastrozole (18%), letrozole (18%) or fulvestrant (18%). A total of 821 patients, comprising 7% of the patients who received 1st-line ET, received at least 3 consecutive lines of ET without CT. The majority of these patients received exemestane (20%), tamoxifen (19%) or fulvestrant (19%) in the 3rd line. Among these 821 patients, the median treatment durations were 9, 6, and 3 months in the 1st, 2nd, and 3rd lines, respectively. Median durations for each ET agent were generally lower in later versus earlier treatment lines (Table). At the time of data cutoff for this study, limited data were available for everolimus treatment (n=21). Conclusions: The large majority of patients did not receive the guideline-recommended target of 3 lines of ET. Additionally, the shorter durations of therapy observed within each subsequent line of ET suggest that there may be diminishing returns for sequential use of ET monotherapies for HR+/HER2- mBC. These findings indicate an unmet need for more effective alternatives to available ET monotherapies after the initial ET discontinuation during the study period (2002-2012). Citation Format: Elyse Swallow, Jenny Wang, Darren Thomason, Ruo-Ding Tan, Andrew Kageleiry, James Signorovitch. Real-world treatment durations without chemotherapy (CT) for hormone-receptor-positive (HR+)/human epidermal growth factor receptor-2-negative (HER2-) metastatic breast cancer (mBC) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-13-08.