Extended Endocrine Therapy for Early-Stage Breast Cancer: How Do We Decide?

While the majority of hormone receptor-positive breast cancers are diagnosed at an early stage, a significant proportion of patients will develop disease recurrence, especially late disease recurrence, despite current therapeutic approaches. In this review, we examine the data pertaining to the choice of endocrine and extended endocrine therapy, outline how to identify patients that may benefit from extended therapy, and discuss prognostic tools to assist with patient selection. The risk of breast cancer recurrence persists after 5 years, is cumulative, and is indefinite. In attempts to mitigate these risks, studies have evaluated the use of extended endocrine therapy. Overall survival benefit has been demonstrated with extended tamoxifen, whereas extended aromatase inhibitors have shown modest disease-free survival benefit. Therapeutic approaches for individual patients will depend on the perceived risk of recurrence, likely benefit of extended therapy, tolerability of current endocrine therapy, and patient preference.