The optimal duration of adjuvant endocrine therapy in early luminal breast cancer: A concise review

•Risk of breast cancer relapse extended after 5 years of adjuvant endocrine therapy.•Multiple clinical trials tested efficacy and safety of extending adjuvant ET.•Clinical data currently at our disposal are conflicting.•We reviewed all the major trials concerning this topic.•We reviewed also evidences from translational researches. Patients with luminal early breast cancer are at risk of relapse, even after five years of adjuvant endocrine therapy. To date, no biomarkers have been clinically validated to identify those patients at risk of late recurrence, who might benefit from extended adjuvant endocrine therapy. In recent decades, multiple clinical trials have tested the role of extending adjuvant endocrine therapies in patients with luminal disease. However, the data currently at our disposal are conflicting. This article reviews all the major trials concerning extended adjuvant endocrine regimens, and formulates some general conclusions and hypotheses of future study.