Evaluate the Efficacy and Safety of Adebrelimab Combined With Chemotherapy With or Without Radiotherapy as Neoadjuvant Treatment for HER2-Negative Locally Advanced Breast Cancer

Inclusion Criteria:

1. Female patients aged between 18 and 70 years old.

2. Pathologically confirmed as invasive breast cancer, with immunohistochemicalstaining indicating HER2 negativity, as specifically referenced in the guidelines ofthe American Society of Clinical

3. Oncology/College of American Pathologists (ASCO/CAP).

4. Clinical stage II-III, patients who are planned to undergo neoadjuvant treatment todownstage for surgery or who wish to have breast-conserving surgery afterneoadjuvant treatment.

5. The breast tumor is suitable for SBRT (stereotactic body radiotherapy) (tumordistance from the skin > 5 mm, without invasion of the ribs or intercostal muscles).

6. No distant metastasis detected by clinical examination combined with imaging studies (including but not limited to liver ultrasound, chest CT, bone scan, PET-CT).

7. Adequate organ function (hemoglobin ≥ 100 g/L, white blood cells ≥ 3×10⁹/L,neutrophils ≥ 1.5×10⁹/L, platelets ≥ 80×10⁹/L; creatinine ≤ 132 μmol/L; alanineaminotransferase/aspartate aminotransferase ≤ 2.5×upper normal limit [UNL]).

8. Capable of undergoing breast magnetic resonance imaging (MRI) scans. Eligible forfollow-up conditions.

9. The subject is able to sign the informed consent form to participate in the study.

10. Women of childbearing age are not pregnant, not breastfeeding, and are usingeffective contraception.

Exclusion Criteria:

1. Prior receipt of chest radiotherapy, chemotherapy, or immunotherapy.

2. History of other malignancies, with the exception of adequately treated basal cellcarcinoma of the skin, carcinoma in situ of the cervix, or papillary thyroid cancer.

3. Patients with active fibroconnective tissue diseases, risk of active autoimmunediseases, or a history of autoimmune diseases that may involve the central nervoussystem, including but not limited to Crohn's disease, ulcerative colitis, systemiclupus erythematosus, sarcoidosis, Wegener's syndrome, granulomatosis withpolyangiitis, Graves' disease, rheumatoid arthritis, hypophysitis, uveitis,autoimmune hepatitis, systemic sclerosis, Hashimoto's thyroiditis, autoimmunevasculitis, and autoimmune neuropathies (e.g., Guillain-Barré syndrome). Thefollowing exceptions apply: Type I diabetes mellitus, stable hypothyroidism onhormone replacement therapy (including hypothyroidism due to autoimmune thyroiddisease), psoriasis or vitiligo not requiring systemic therapy, and autoimmunediseases caused by B cells or anti-self-antigen antibodies.

4. Pulmonary disease defined as ≥ Grade 3 according to the NCI-CTCAE v5.0; history ofinterstitial lung disease (ILD) requiring corticosteroid treatment (includingpulmonary fibrosis or radiation pneumonitis), or current ILD or ≥ Grade 2 radiationpneumonitis.

5. Severe comorbidities or active diseases: a) History of severe cardiovascular and cerebrovascular diseases, including but notlimited to: i. Severe cardiac rhythm or conduction abnormalities, such asventricular arrhythmias requiring clinical intervention, or third-degreeatrioventricular block; ii. QT interval prolongation at rest (QTc > 450 msec inmales or > 470 msec in females); iii. Acute coronary syndrome, congestive heartfailure, aortic dissection, stroke, or other Grade 3 or higher cardiovascular andcerebrovascular events within 6 months prior to the first dose; iv. Presence ofheart failure with New York Heart Association (NYHA) functional class ≥ II. b) Poorly controlled diabetes for > 1 month: fasting blood glucose > 10 mmol/L, orpostprandial 2-hour blood glucose > 13 mmol/L. c) Poorly controlled psychiatric disorders with an episode or exacerbation withinthe past 6 months. d) Active infection. e) Positive for human immunodeficiency virus (HIV) antibodies.Other diseases that are not suitable for immunotherapy, or a history of othermalignancies.

6. Presence of severe internal medical conditions that may affect radiotherapy orimmunotherapy.

7. Pregnant or breastfeeding women.

8. History of allergy to components of radiotherapy or immunotherapy.