Single-dose Preoperative Partial Breast Irradiation in Low-risk Breast Cancer Patients

This study is testing a single dose of targeted radiation (partial breast irradiation) given before surgery for women with small, low-risk breast cancer. The idea is that treating the tumor site with one dose of radiation before removing it may be just as effective as standard radiation after surgery, while being more convenient. **You may be eligible if...** - You are a woman aged 50 or older - You have a small (stage T1N0), single-focus breast cancer detected on imaging - Your tumor is hormone receptor-positive (ER+) and HER2-negative - The tumor is grade 1 or 2 (low to intermediate grade) and is a non-lobular invasive cancer - Your lymph nodes show no cancer spread (negative sentinel node) **You may NOT be eligible if...** - You carry a BRCA1, BRCA2, or CHEK2 gene mutation - The cancer has spread to distant parts of the body - You have had breast cancer or DCIS before - You have a connective tissue disease (like lupus or scleroderma) - Your tumor has an extensive in-situ (DCIS) component or is lobular carcinoma - You need chemotherapy or HER2-targeted therapy for this cancer Talk to your doctor to see if this trial is right for you.