The study is a prospective randomized control clinical trial which is sponsored by the researchers. The purpose of this study is to determine the effectiveness of Gonadotropin-Releasing hormone agonist on ovarian function for premenopausal breast cancer patients during chemotherapy. The premenopausal breast cancer patients will be randomly (1:1) enrolled to receive standard chemotherapy with the GnRH agonist goserelin (goserelin group) or standard chemotherapy without goserelin (chemotherapy alone group). All patients are stratified according to age (<35years vs.36-44years), hormone receptor status (HR+ or ER+ vs.HR- and ER-), chemotherapy regimen(3-4 cycles vs.6-8 cycles, and cyclophosphamide-based vs.noncyclophosphamide).The follow-up time will be at least 2years. The ovarian failure, follicle-stimulating hormone, estradiol and anti-Mullerian hormone, pregnancy outcomes and disease-free and overall survival will be compared between two groups to evaluate the effectiveness of protect against ovarian failure.

Inclusion Criteria:

• The patients signed the written informed consent.
• Histologically proven stage I, II, or III breast cancer
• Must be candidates for adjuvant or neoadjuvant chemotherapy,
• Must be premenopausal.
• Trastuzumab is permitted in patients with human epidermal growth factor receptor 2 (HER2) overexpressing tumors.

Exclusion Criteria:

• The patients were previous chemotherapy;
• Evidence of distant metastases;
• Other malignancies in the previous 5 years.
• The patients were using GnRHa, progesterone, stimulate ovulation drugs, oral contraceptives, aromatase inhibitors, intrauterine device with hormone, subcutaneous preparations contraceptive drugs such as hormone drugs and instruments during 3 month preceding the start of chemotherapy.
• Pregnancy or lactation.