Study on How the Immune System Responds to Neoadjuvant Abemaciclib in Breast Cancer

Inclusion Criteria

• Have a breast cancer diagnosis that is operable and at stage I, II, or III, with hormone receptor-positive and HER2-negative status.
• Be post-menopausal, which can be confirmed by age, lack of menstruation, or specific hormone levels.
• Have a breast tumor that is 1 cm or larger and suitable for tissue sampling.
• Be planned for surgery or systemic therapy, with two weeks of pre-surgery endocrine therapy considered appropriate.
• Be at least 18 years old.
• Have a performance status score of 0 to 2, indicating good overall health.
• Have adequate organ function based on specific blood test results.
• Be able to swallow pills.
• Have no recurrence of previous breast cancer if there was a history of cancer in the other breast.
• Have stopped taking tamoxifen or raloxifene at least 28 days before joining the study.
• Have stopped hormone replacement therapy at least 7 days before starting treatment.
• Be able to understand and sign a consent form.
• If of childbearing potential, have a negative pregnancy test and agree to use effective contraception during and after treatment, although this mainly applies to pre-menopausal women.

Exclusion Criteria

• Have active metastatic, inflammatory, or locally recurrent breast cancer.
• Have serious or uncontrolled medical conditions that could interfere with the study, such as severe lung disease, kidney problems, or chronic diarrhea.
• Be pregnant, breastfeeding, or pre-menopausal.
• Have severe malabsorption issues or conditions affecting nutrient absorption.
• Have mental health conditions that prevent understanding the study.
• Have received chemotherapy, radiotherapy, or other cancer treatments for the current breast cancer diagnosis.
• Be taking other investigational drugs for breast cancer.
• Have allergies to similar drugs used in the study.
• Have uncontrolled illnesses like infections, heart failure, or unstable heart conditions that could affect participation.