Concurrent Gonadotropin-Releasing Hormone Agonist Administration with Chemotherapy Improves Neoadjuvant Chemotherapy Responses in Young Premenopausal Breast Cancer Patients

PURPOSE: This study aimed to determine the oncologic efficacy of gonadotropin-releasing hormone (GnRH) agonist treatment concurrent with chemotherapy in a neoadjuvant setting. METHODS: A retrospective analysis was performed on 332 cases of invasive breast cancer in patients who were <40 years old at diagnosis and received GnRH agonists concurrent with neoadjuvant chemotherapy (GnRH agonist group) or neoadjuvant chemotherapy alone (neochemotherapy-alone group) from December 2010 to September 2014. Pathologic complete response rates (pCR) and Ki-67 changes were evaluated between the two groups. RESULTS: Median age was 32±3.9 and 36±3.0 years in the GnRH agonist group and neochemotherapy-alone group, respectively (p<0.001). After adjustment for tumor size, grade, lymph node metastasis, hormone receptor (HR) status, and chemotherapy regimen, the GnRH agonist group exhibited a higher pCR rate with an odds ratio (OR) of 2.98 (95% confidence interval [CI], 1.37-6.34) and a greater decrease in Ki-67 expression after treatment (p=0.05) than the neochemotherapy-alone group. For HR-negative tumors, the GnRH agonist group showed a higher pCR rate (multivariate OR, 3.50; 95% CI, 1.37-8.95) and a greater decrease in Ki-67 expression (p=0.047). For HR-positive breast cancer, the pCR rate, change in Ki-67 index, and clinical response were higher, and preoperative endocrine prognostic index scores were lower, in the GnRH agonist group, but these did not reach statistical significance. CONCLUSION: Concurrent administration of GnRH agonists during neoadjuvant chemotherapy improved pCR rates and suppressed Ki-67 expression, especially in HR-negative tumors.