After the completion of primary treatment(surgery and/or adjuvant chemotherapy, radiotherapy could be given concurrently with study medication), eligible patients will be randomized to receive Zoladex plus tamoxifen or tamoxifen alone. The duration of study medication along with the follow-up will be 18 months, or until disease recurrence,or discontinuation of study therapy (as a result of an adverse event, a patient's request, or an investigator's decision), further treatment will be at investigator's discretion.