Radiotherapy and Long-term Outcomes in Early Breast Cancer With SLNB Omission

This prospective, multicenter observational cohort study evaluates long-term outcomes in patients with early-stage invasive breast cancer who undergo breast-conserving surgery without sentinel lymph node biopsy or other axillary surgery and subsequently receive adjuvant radiotherapy. The study will evaluate recurrence, survival, radiotherapy-related toxicities, and quality of life. Radiotherapy will be delivered according to routine clinical practice at each participating institution without protocol-mandated treatment assignment. Detailed radiotherapy characteristics, including treatment volume, technique, dose and fractionation, tumor-bed boost, and radiation dose to axillary lymph node levels I-III, will be prospectively collected to evaluate their associations with clinical outcomes.