Evaluating Omitting of Internal Mammary Irradiation Among Early Stage Intermediate Risk (N1) Breast Cancer

This study is investigating whether leaving out radiation to the internal mammary lymph nodes (nodes along the breastbone) is safe for early-stage breast cancer patients with 1 to 3 positive lymph nodes, potentially reducing side effects without worsening outcomes. **You may be eligible if...** - You have been diagnosed with invasive breast cancer - You had surgery (either mastectomy or lumpectomy) and removal of lymph nodes under your arm - You had 1 to 3 lymph nodes that tested positive for cancer - Your cancer has certain high-risk features such as a large tumor, young age, or triple-negative or HER2+ status **You may NOT be eligible if...** - You had 4 or more positive lymph nodes - You had distant metastases at diagnosis - Your cancer spread to the skin or chest wall Talk to your doctor to see if this trial is right for you.