Extended adjuvant endocrine therapy in early breast cancer: finding the individual balance

Endocrine therapy (ET) is a cornerstone in the management of patients with hormone receptor-positive early breast cancer, which accounts for over 70% of cases worldwide. The efficacy of adjuvant ET for 5 years in reducing the risk of recurrence and improving survival outcomes is well documented. However, the risk for late relapses, occurring >5 years after initial treatment, has prompted exploration of longer treatment durations. Extending ET beyond the traditional 5-year period offers additional benefit in reducing the risk of recurrence and improving long-term outcomes. Nevertheless, determining the optimal duration and identifying suitable candidates for extended therapy is often nuanced. This review aims to comprehensively evaluate the current landscape of extended ET in breast cancer management. It provides an overview of the rationale behind extending endocrine treatment in both premenopausal and postmenopausal women, with a focus on clinical trials and observational studies supporting extended therapy. Furthermore, it emphasizes the significance of considering associated toxicities in patient management. It also explores novel strategies involving the combination of ET with new drugs, leading to an evolution of treatment paradigms that may make the need for extended therapy obsolete.