Neoadjuvant SBRT Followed by Nab-Paclitaxel Combined With Toripalimab in HR+/HER2- Breast Cancer

HR-positive and HER2-negative (HR+/HER2-) breast cancer is the most common subtype of breast cancer. Although this subtype is generally associated with favorable overall survival, patients with high-risk features remain at substantial risk for late recurrence and distant metastasis. In particular, those presenting with large primary tumors (cT3 or higher) or axillary lymph node involvement face a significantly elevated risk of locoregional recurrence and distant metastasis relative to patients with earlier-stage, lower-risk disease. In recent years, the role of neoadjuvant therapy in the comprehensive treatment of breast cancer has gained increasing attention. The pathological complete response (pCR) rate following neoadjuvant therapy is closely associated with long-term survival. However, compared to HER2+ or triple-negative breast cancer, HR+/HER2- breast cancer patients exhibit a significantly lower pCR rate with neoadjuvant chemotherapy alone. Neoadjuvant chemotherapy combined with immunotherapy has become a key treatment strategy for TNBC, this combination also improves pCR rates in HR+/HER2- breast cancer, though the benefit is less pronounced than in TNBC. Radiotherapy not only releases a large number of tumor antigens and inflammatory signals to enhance systemic anti-tumor immune responses, but also promotes the exposure of tumor cell surface antigens, thereby increasing the immunogenicity of the tumor microenvironment. The synergistic effect of radiotherapy and immunotherapy, when combined with chemotherapy, may further improve treatment efficacy. Based on these, we designed this clinical trial evaluating the effect of neoadjuvant radiotherapy combined with de-escalated chemotherapy and immunotherapy, aiming to explore its potential to improve pCR rates and long-term outcomes in HR+/HER2- breast cancer patients. Enrolled patients will receive four cycles of single-agent Nab-Paclitaxel plus Toripalimab within one week after stereotactic radiotherapy, followed by surgery and subsequent adjuvant therapy. Postoperative pCR rate and prognosis of participants will be analyzed in our clinical study.