The purpose of this study is to examine the efficacy and safety as well as the characteristics of the female hormone and study medications after administration in pre-menopausal women with advanced or recurrent breast cancer who were randomised in a 1:1 ratio to either of the two treatment groups; the ZD9393 3.6 mg depot group or ZD9393 10.8 mg depot group, both given in combination with tamoxifen tablets.