Development of a Prognostic Factor Index Among Women With HR+/HER2− Metastatic Breast Cancer in a Community Oncology Setting

Background 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). Materials and Methods This retrospective study used electronic health record data of patients in the United States from community oncology practices from January 1, 2008 to April 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 the 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 1 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 < .05) shorter in patients with 1 and 2+ prognostic factors compared with patients with 0. 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.