This study is for premenopausal women (18-55 years old) with a specific type of advanced breast cancer. The study focuses on ovarian suppression, which means stopping the ovaries from producing hormones. This is done using a medicine called ZOLADEX. Researchers will check if ZOLADEX works by measuring a hormone called luteinizing hormone (LH).

Participants cannot be postmenopausal or have a body mass index (BMI) under 18 or over 35. They must not have had certain surgeries or recent radiation treatments. If they are taking certain medications, these must be stable before joining the trial.

• Participants may need to visit the clinic regularly for assessments.
• Participants need to use effective nonhormonal birth control methods during the study.
• There could be side effects, so participants should consider their health conditions and discuss with their doctors.

Participants must not have serious medical conditions that could affect the study or their safety. They should not be pregnant or breastfeeding, and they need to understand and agree to the study requirements.