This study focuses on preoperative treatment modalities for luminal-type locally advanced breast cancer. Based on modern precision radiotherapy technologies such as MRI-Linac, CyberKnife, and VMAT, it aims to compare the pCR rate, breast conserving surgery (BCS) rate, progression-free survival (PFS), and treatment-related side effects between preoperative neoadjuvant chemotherapy and preoperative neoadjuvant SBRT combined with chemotherapy in patients with this type of breast cancer. The goal is to provide new strategic options for the preoperative treatment of luminal-type locally advanced breast cancer.

Breast cancer is a tumor with high tumor heterogeneity, and treatment outcomes vary significantly across different molecular subtypes. In recent years, the emergence of novel treatment methods has significantly improved the overall survival and progression-free survival of patients with early-stage, especially metastatic tumors. However, a portion of patients with locally advanced breast cancer (LABC) still have poor prognoses. As early as the 1970s, preoperative radiotherapy was applied to locally advanced breast cancer to increase resectability, but due to limitations in radiotherapy techniques and other factors, preoperative radiotherapy increased the incidence of acute toxic reactions and postoperative complications. Compared to traditional postoperative radiotherapy, neoadjuvant radiotherapy has several theoretical advantages, such as more precise tumor target localization, optimization of breast reconstruction radiotherapy strategies, increased tumor downstaging to improve breast-conserving surgery opportunities, and improved pathological complete response rates, potentially eliminating the need for breast surgery. With the advent of the era of precision radiotherapy, modern radiotherapy technologies have provided solutions to reduce the acute toxic reactions associated with preoperative radiotherapy. This study focuses on preoperative treatment modalities for luminal-type locally advanced breast cancer. It aims to compare the pCR rate, breast-conserving surgery (BCS) rate, progression-free survival (PFS), and treatment-related side effects between preoperative neoadjuvant chemotherapy and preoperative neoadjuvant SBRT combined with chemotherapy in these patients. The goal is to provide new strategic options for the preoperative treatment of luminal-type locally advanced breast cancer.

Inclusion Criteria:

1. Pathologically confirmed invasive breast cancer ;
2. Breast MRI showing stages IIB to IIIC (2017 AJCC 8th edition staging);
3. Clinical staging confirmed by chest MRI and/or axillary ultrasound, as well as CT scans of the neck, abdomen, and pelvis, and bone scintigraphy, including T and N staging and assessment of distant metastasis;
4. Karnofsky performance score ≥80 or ECOG performance status of 0-1;
5. No history of allergies to doxorubicin, cyclophosphamide, paclitaxel/docetaxel;
6. No prior exposure to radiotherapy, chemotherapy, endocrine therapy, targeted therapy, or immunotherapy.

Exclusion Criteria:

1. History of malignancy at other sites, excluding curable non-melanoma skin cancer and carcinoma in situ of the cervix;
2. Inability to complete MRI;
3. Inflammatory breast cancer;
4. Bilateral or multifocal primary tumors;
5. Active infection currently present; clinically evident heart disease; myocardial infarction or cerebrovascular accident within 6 months prior to enrollment.