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Background: The current randomized, controlled, multicenter clinical trial was conducted to investigate the efficacy of concurrent neoadjuvant chemotherapy (NCT) and estrogen deprivation in patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer.Methods: Eligible patients with AJCC stage IIB to stage IIIC, ER-positive, HER2-negative breast cancer were enrolled and randomly assigned to receive NCT with or without estrogen deprivation. The primary endpoint was the objective response rate (ORR).Results: A total of 249 patients were assigned to either neoadjuvant chemoendocrine therapy (NCET) (125 patients) or the NCT group (124 patients). In the intention-to-treat analysis, the ORR was found to be significantly higher in the NCET group compared with the NCT group (84.8% vs 72.6%; odds ratio, 2.11 [95% CI, 1.13-3.95; P = .02). The efficacy of NCET was more prominent in tumors with a higher Ki-67 index (>20%), with an ORR of 91.2% reported in the NCET group versus 68.7% in the NCT group (P = .001). The pathologic complete response and pathological response rates did not differ significantly between the 2 groups. Although there was no significant difference with regard to progression-free survival (PFS) between the 2 groups (P = .188), patients with a higher baseline Ki-67 index appeared to derive a greater PFS benefit from NCET (2-year PFS rate of 91.5% in the NCET group vs 76.5% in the NCT group; P = .058). Adding endocrine agents to NCT did not result in significant differences in adverse events (grade 3 or 4; graded according to National Cancer Institute Common Terminology Criteria for Adverse Events [version 3.0]) between the 2 groups.Conclusions: The addition of estrogen deprivation to NCT appears to improve the clinical response in patients with ER-positive, HER2-negative breast cancer, especially for those individuals with a higher Ki-67 index. Patients with a higher Ki-67 index might derive more PFS benefit from concurrent neoadjuvant treatment. [ABSTRACT FROM AUTHOR]