Abstract P5-08-08: Baseline (BL) characteristics, treatment (tx) patterns, and outcomes in patients with hormone receptor (HR)+ vs HR– HER2+ disease from the SystHERs registry
Authors: Cobleigh M , Yardley DA , Brufsky A , Rugo H , Swain S , Kaufman PA , Tripathy D , Mayer M , Hurvitz S , O'Shaughnessy J , Mason G , Chu L , Antao V , Beattie M , Yoo B , Jahanzeb M 
Published: March 2017

Introduction HR+ metastatic breast cancer (MBC) generally has a more indolent course than HR– MBC. Less is known about differences in BL characteristics and disease outcomes by HR status in HER2+ MBC in the modern tx setting where patients (pts) may recur after adjuvant therapy. SystHERs is an ongoing, prospective, observational cohort study of HER2+ MBC pts. Here we describe BL characteristics, tx patterns, and outcomes by HR status and MBC diagnosis type.

Methods SystHERs enrolled pts aged ≥18 years and within 6 months of MBC diagnosis. Locally-determined HR status was captured at initial diagnosis and/or disease recurrence; HR+ was defined as ER+ and/or PR+ disease in primary (early BC) or MBC. Tx data are shown for pts ≥9 months from MBC diagnosis to capture the completion of chemotherapy and the addition of hormonal therapy during maintenance tx. Median overall survival (OS; Kaplan-Meier) and the hazard ratio (Cox regression) were estimated.

Results As of Feb 2016, data were available for 872 eligible pts with known HR status; 70% had HR+ disease and 50% had de novo MBC. Median follow-up from MBC diagnosis was 16.5 months (range, 0.4–49.4 months). Clinically important BL demographics and disease characteristics with noticeable differences are presented in Table 1. More black (vs white) pts were observed to be HR–. More recurrent (vs de novo) pts were observed to be HR+.

MBC tx choices may be influenced by adjuvant tx. Table 2 shows the most common first-line tx regimens in de novo vs recurrent pts with HR+ HER2+ disease and ≥9 months from MBC diagnosis. Among these pts, 60% de novo and 56% recurrent pts received any hormonal therapy. The most common first-line tx regimen for pts with HR– disease was chemotherapy + HER2-targeted therapy (92%).

There were 88 (15%) and 55 (21%) deaths in the HR+ and HR– groups, respectively. Median OS was not reached for either group, but the hazard ratio favored pts with HR+ disease (log-rank P=0.026; hazard ratio 0.683; 95% CI 0.488–0.957).

Table 1. BL characteristics HR+ HER2+ (n=608)HR– HER2+ (n=264)Race, %  White8272Black1321MBC diagnosis type, %  De novo4758Recurrent*5342Visceral disease, %6375No significant differences in other characteristics by HR status (eg, sex, ethnicity, education, menopausal status, performance status, number of metastatic sites at diagnosis). *Pts with prior adjuvant therapy: HR+, 89%; HR–, 83%.

Table 2. Most common first-line tx regimens in pts with HR+ HER2+ disease and ≥9 months from MBC diagnosis De novo (n=227)Recurrent (n=235)Chemotherapy + HER2-targeted therapy + hormonal therapy, %4938Chemotherapy + HER2-targeted therapy only, %3741HER2-targeted + hormonal therapy only, %1014

Conclusions In SystHERs, 70% of pts with HER2+ MBC had HR+ disease. A higher percentage of recurrent pts had HR+ disease vs de novo pts, perhaps suggesting selective elimination of HR– clones during adjuvant tx. While black pts are known to be more likely to develop HR– HER2– BC, our results show that HR– HER2+ disease is also more common in black pts, suggesting a proclivity for this population to develop HR– MBC regardless of HER2 status. In these early results, survival was higher in pts with HR+ HER2+ MBC.

Citation Format: Cobleigh M, Yardley DA, Brufsky A, Rugo H, Swain S, Kaufman PA, Tripathy D, Mayer M, Hurvitz S, O'Shaughnessy J, Mason G, Chu L, Antao V, Beattie M, Yoo B, Jahanzeb M. Baseline (BL) characteristics, treatment (tx) patterns, and outcomes in patients with hormone receptor (HR)+ vs HR– HER2+ disease from the SystHERs registry [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-08.