This study is for young women with early-stage breast cancer. The study checks if adding adjuvant chemotherapy (ACT) to ovarian function suppression (OFS) and endocrine therapy (ET) helps them live longer without cancer returning. OFS stops the ovaries from making estrogen, a hormone that can help cancer grow. The study is for women who haven’t reached menopause and have specific types of breast cancer that are estrogen receptor (ER)-positive and HER2-negative. Eligible participants need a 21-gene recurrence score (Oncotype DX RS) of 25 or less. This score helps predict cancer's return risk. Participants must be 18 or older and still have functioning ovaries.

• Study participation may include multiple visits and treatments.
• There may be risks, like chemotherapy side effects.
• Benefits could include better survival rates and compensation may be available.

Before joining, participants must understand the study and agree to share health info. They must meet specific health criteria and can’t have certain other health issues. This study aims to find better treatment options for young breast cancer patients.