51 - Systemic Therapy of Hormone-Sensitive HER2-Negative Breast Cancer: Adjuvant and Neoadjuvant

Abstract

The majority of breast cancers are estrogen receptor and/or progesterone receptor (ER/PR)-positive and human epidermal growth factor-2 (HER2)-negative. Recent advances have led to improvements in survival outcomes for early-stage ER/PR-positive, HER2-negative breast cancer, although late recurrence remains an ongoing clinical challenge. Systemic therapy for early-stage ER/PR-positive, HER2-negative breast cancer is usually administered postoperatively in the adjuvant setting, although neoadjuvant therapy is used in limited instances. The primary types of systemic therapies used in the management of early-stage ER/PR-positive, HER2-negative breast cancer are endocrine agents and, in some cases, chemotherapy. Emerging data support use of targeted therapies in certain scenarios. Treatment decisions are complex and depend on multiple factors including menopausal status, tumor characteristics, nodal status, comorbidities, and patient preferences. In many cases, multiparameter gene expression assays can help guide decisions about systemic therapy. In this chapter, we will review the current approach to systemic therapy for ER/PR-positive, HER2-negative early-stage breast cancer. We will discuss strategies used to guide selection of therapies, review key trials that have led to the current standard of care, and discuss ongoing unanswered questions and future directions.