ObjectivesNeoadjuvant endocrine therapy (NET) has demonstrated efficacy in postmenopausal patients with hormone-responsive and HER2-negative breast cancer. However, few data are available on NET in premenopausal women. This trial was designed to compare the effectiveness of neoadjuvant chemotherapy (NCT) with NET in premenopausal patients with hormone-responsive, HER2-negative, and lymph node-negative breast cancer.MethodsIn this prospective, randomized study, premenopausal patients with hormone-responsive, HER2-negative, and lymph node-negative breast cancer were recruited. The enrolled patients were randomly assigned (1:1) to receive either NCT or NET with goserelin and tamoxifen, followed by goserelin and anastrozole. The primary purpose was to evaluate the non-inferiority of NET to NCT using a clinical response rate assessed by ultrasound.ResultsA total of 68 patients were assigned to receive either NCT (n = 31) or NET (n = 37). The clinical response rate was 16.1% for NCT and 35.1% for NET (estimated difference 19.0%, 95%CI: -1.1%-39.1%, non-inferior = 0.002). The rates of breast-conserving surgery were not significantly different between the NCT and NET groups (90.3% vs 83.8%, = 0.494).ConclusionsA 35.1% clinical response rate was observed in premenopausal patients after NET. However, this study was underpowered to conclude the non-inferiority of NET to NCT because of its early closure.Trial registrationClinicalTrials.gov NCT02535221.