Evolving Role of Neoadjuvant Endocrine Therapy in Hormone Receptor Positive Breast Cancer: a Review

Neoadjuvant endocrine therapy (NET) has historically been used in the treatment of hormone receptor (HR)-positive breast cancer (BC) in older and more frail patients. There has been longstanding and renewed interest in the use of endocrine therapy in the neoadjuvant setting. We performed a literature review to outline recent advances in its use.

NET is being tested in combination with chemotherapy as well as with targeted therapeutic agents in the neoadjuvant setting, though rates of pathologic complete response (pCR) and long-term outcomes are not shown to be considerably different than with single-agent neoadjuvant therapy. However, response to NET provides important information regarding tumor biology that helps inform additional therapy, including administration of chemotherapy in the neoadjuvant setting and omission of radiation therapy in the adjuvant setting. Ongoing research into molecular mechanisms driving endocrine responsiveness show promising results in identifying predictive biomarkers for treatment response and long-term outcomes.

In addition to downstaging disease and increasing rates of breast conservation therapy, NET has progressively become part of a broader neoadjuvant strategy in the treatment of HR + BC. As the role of NET evolves to become a framework for identifying drug responsiveness and resistance, the development of potential individualized targets for treatment represents the next step towards personalized cancer care and ultimately towards improving long-term outcomes for patients with HR + BC.