Development of a Prognostic Factor Index among Women with HR+/HER2- Metastatic Breast Cancer in a Community Oncology Setting

ABSTRACT Purpose This study explored the impact of multiple prognostic factors on patient overall survival (OS) and real-world progression-free survival (rwPFS) for patients with hormone receptor positive (HR+)/human epidermal growth factor 2 negative (HER2-) metastatic breast cancer (MBC). Methods This retrospective study used electronic health record data of US patients from community oncology practices from 1/1/2008 to 4/30/2017. Eligibility included HR+/HER2- MBC diagnosis in 2008 or later and prior systemic therapy for MBC. An index variable was created to assess the effect of multiple clinical prognostic factors collectively, including liver metastases (LM), primary endocrine resistance (PER), negative progesterone receptor (PR-) status, and high tumor grade (TG). Patients were grouped based on the number of prognostic factors present at MBC diagnosis: 0, 1, and 2+. Differences in rwPFS and OS from start of first line therapy were evaluated by Kaplan-Meier method and multivariable Cox proportional hazards regression. Results Approximately 29.1% of the 378 eligible patient sample had 0, 36.0% had 1, and 34.9% had 2+ prognostic factors. For the patients with one of the prognostic factors, 24.3% had high TG, 14.7% were LM+, 39.7% had PER, and 21.3% were PR-. Univariate and multivariate results showed that rwPFS and OS were significantly (p Conclusions The individual prognostic factors and the prognostic factor index may enable early identification of patients with a less favorable prognosis across the HR+/HER2- MBC population and help inform treatment decisions in difficult to treat populations.