Breast Re-irradiation After Second Ipsilateral Lumpectomy

This study tests re-irradiation (a second course of radiation therapy) after a second lumpectomy for women who have had a breast cancer recurrence in the same breast (ipsilateral recurrence) but have already received radiation before. **You may be eligible if...** - You are 40 years of age or older - You have been diagnosed with ER-positive, HER2-negative breast cancer - You have had a second lumpectomy for a recurrence in the same breast - At least 18 months have passed since your last breast radiation treatment - Your cancer has a low genomic risk score (Oncotype low or ultra-low) **You may NOT be eligible if...** - Your cancer has spread to lymph nodes or distant organs - You have a BRCA gene mutation - You are pregnant - Your remaining breast tissue after surgery is too limited for radiation Talk to your doctor to see if this trial is right for you.