Abstract P2-08-20: Clinical outcomes among HR+/HER2- metastatic breast cancer patients with multiple metastatic sites

Background: Hormone receptor-positive, human epidermal growth factor receptor-2-negative (HR+/HER2-) is the most common type of metastatic breast cancer (mBC). While overall the prognosis among these patients is poor with short progression-free survival (PFS) and overall survival (OS), those with multiple metastatic sites (multiple mets) may have even worse clinical outcomes due to multiple organ involvement. This real-world study examined clinical outcomes among HR+/HER2- mBC patients with multiple mets. Methods: In this retrospective chart review, a sample of postmenopausal women with HR+/HER2- mBC was collected from community-based oncology practices in the US. Patients were required to have failed a non-steroidal aromatase inhibitor and later initiated a new treatment (defined as the index therapy) for mBC between July 1, 2012 and April 15, 2013. Patients were classified into two mutually exclusive groups: multiple mets or single metastatic site (single met), based on the number of non-lymph-node metastatic sites at index therapy initiation. PFS, time on treatment (TOT), and OS were compared between the two study groups using Kaplan-Meier analyses with log-rank tests and multivariable Cox proportional hazards models adjusting for baseline characteristics, including age, race, insurance, mBC type, and months from initiation of last adjuvant endocrine therapy to mBC diagnosis, index therapy type, index therapy line, adjusted Charlson comorbidity index (CCI), Eastern Cooperative Oncology Group (ECOG) performance status, and prior chemotherapy for mBC. Patients without an event were censored at the last follow-up. In addition, separate Cox proportional hazard models were conducted including an interaction term between line of therapy and study group to assess the impact of multiple mets on clinical outcomes across different lines of therapy. Results: A total of 408 patients in the single met group and 291 patients in the multiple mets group were included. Patients with multiple mets had worse ECOG performance status and a higher rate of prior chemotherapy use for mBC compared with patients in the single met group. Relative to patients with single met, patients with multiple mets were associated with significantly shorter PFS (log-rank test p Conclusion: Among HR+/HER2- mBC patients, those with multiple mets had significantly worse clinical outcomes, highlighting substantial disease burden and unmet need for more efficacious treatment for these patients. Citation Format: Xie J, Hao Y, Li N, Lin PL, Ohashi E, Koo V, Wu EQ. Clinical outcomes among HR+/HER2- metastatic breast cancer patients with multiple metastatic sites. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-08-20.