Abstract P1-14-03: Chemotherapy and endocrine therapy treatment patterns among patients with hormone receptor positive (HR+)/HER2 negative advanced breast cancer
Authors: Hao Y , Engel-Nitz NM , Sullivan J , Henk HJ , Willemann Rogerio J , Newcomer L 
Published: August 2014

Background: National Comprehensive Cancer Network breast cancer guidelines suggest optimized sequencing of endocrine therapy prior to chemotherapy use for patients who are HR+/HER2-, but it is unclear how those recommendations translate into clinical practice. This study examined sequencing of endocrine and chemotherapy treatment to better understand real-world treatment patterns for HR+/HER2- advanced breast cancer.

Methods: This retrospective study examined physician-reported clinical data on patients with breast cancer (BC) linked to medical and pharmacy claims (2008-2012) from a large national US health plan. Patients included in the study had HR+ and HER2- status. Advanced cancer cohorts included patients who were stage IV (SIV) at initial diagnosis, or who developed metastases following initial diagnosis (MET). The first date of diagnosis of advanced cancer or date of metastases following initial diagnosis was designated as index date. Health plan enrollment for 3 months pre- and ≥12-months post- index date was required; patients who died within 12 months after index date and were continuously enrolled were retained. A 3-month baseline period assessed prior treatment; variable post-index follow-up (until disenrollment or Oct 2012) assessed patterns of endocrine and chemotherapy.

Results: Of 317 MET patients, 50% initiated chemotherapy after index date without prior endocrine treatment (CH). Remaining patients (OT) used only endocrine therapy (30%), endocrine therapy prior to chemotherapy (17%), or neither endocrine nor chemotherapy (3%). Compared with OT patients, CH patients were younger (50 vs. 55 years, P&lt;0.001) and progressed faster to metastasis after initial BC diagnosis (243 vs. 1633 days, P&lt;0.001). Although CH patients in the MET group had slightly higher comorbidity prior to their metastatic index date, they had lower levels of any non-lymph node metastases (14% vs. 48%, P&lt;0.001) and visceral metastases (5% vs. 16%, P = 0.001) during follow-up. Among MET patients, 92% of CH patients initiated endocrine therapy during follow-up; endocrine therapy started a mean of 235 days after metastatic index date, compared with a mean starting date for chemotherapy of 41 days post-metastatic index date. In the MET group, 55% of CH later initiated treatment with aromatase inhibitors, compared with 64% of OT patients (P = 0.104). Results were similar in newly diagnosed SIV (n = 71) group: 48% had no evidence of endocrine treatment prior to initiating chemotherapy, and remaining patients used only endocrine therapy (27%), had endocrine therapy prior to chemotherapy (21%), or neither therapy (4%).

Conclusions: In this population of patients with HR+/HER2- advanced breast cancer, a large proportion initiated chemotherapy without prior endocrine therapy. This group of patients might otherwise benefit from a longer progression free period with tolerable toxicity from endocrine therapy. Further investigation of whether a subgroup of these patients started chemotherapy in the adjuvant setting is warranted. For those starting chemotherapy without prior endocrine therapy, understanding treatment sequencing and patient characteristics will help illuminate the extent to which patterns adhere to NCCN guidelines.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-14-03.