Study to Compare Zoladex™ 10.8 mg With Zoladex 3.6 mg in Pre-menopausal Women With Breast Cancer

Inclusion Criteria: * Female ≥20 years and pre-menopausal.Pre-menopausal defined as 1) last menses within 1 year of randomisation, and 2) E2 ≥10 pg/mL and FSH ≤ 30 mIU/mL within 4 weeks of randomisation. * Hormone sensitivity (ER positive) of primary or secondary tumour tissue. * Histological/cytological confirmation of breast cancer and are candidates to receive hormonal therapy as therapy for advanced breast cancer. Exclusion Criteria: * Patients who have received tamoxifen or other hormonal therapies as adjuvant therapy for breast cancer within 24 weeks before randomisation and/or who have received prior treatment with hormonal therapies for advanced breast cancer * Patients who have received LHRHa as adjuvant therapy for breast cancer within 48 weeks before randomisation * Patients who have relapsed during adjuvant hormonal therapy or within 48 weeks after completion of adjuvant hormonal therapy and/or