Current Treatment Patterns Among Postmenopausal Women with HR+/HER2-Metastatic Breast Cancer in US Community Oncology Practices: An Observational Study

Recent approval of novel agents has changed the treatment landscape for post menopausal women with hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2-) metastatic breast cancer (mBC). The objective of this study was to describe contemporary treatment patterns among postmenopausal women with HR+/HER2- mBC in the real-world setting. Data were collected from 64 community oncologists in the US between February and June 2017 using an online medical records extraction tool. Physicians reviewed medical records and provided information on patient demographics and disease characteristics, and treatment regimens. Treatment patterns were described overall and separately by line of therapy and type of treatment received. Discontinuation rates were estimated using Kaplan-Meier analyses to account for censoring. Data were collected on 401 patients. Mean age at the time of mBC diagnosis was 67 years. In the first-line setting, 52.4% of patients received a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor-based regimen, most commonly with an aromatase inhibitor (AI) (39.2%) or fulvestrant (10.0%); 30.2% received endocrine therapy, most commonly an AI (21.4%) or fulvestrant (5.2%) in monotherapy, while 12.7% received a chemotherapy-based regimen. In the second-line setting, 42.9% of patients received a CDK4/6 inhibitor-based regimen, 18.4% received endocrine therapy, and 22.4% received a chemotherapy-based regimen. The 18-month discontinuation rate was 34.5% for patients receiving a CDK4/6 inhibitor-based regimen and 45.8% for patients receiving endocrine monotherapy. CDK4/6 inhibitor-based regimens were the most commonly prescribed treatment in both first- and second-line settings. A wide variety of treatment sequences were observed which suggests an absence of a standard of care for postmenopausal women with HR+/HER2- mBC in real-world practice.