Accelerated Partial Breast Irradiation Versus Standard or Hypofractionated Whole-Breast Irradiation, in Early Breast Cancer, After Breast-conserving Surgery

This study is comparing two radiation approaches for women with early-stage breast cancer who have had breast-conserving surgery (lumpectomy). One approach treats only the area where the tumor was removed (partial breast irradiation), while the other treats the whole breast. Researchers want to know if the more targeted approach is just as effective with fewer side effects. **You may be eligible if you:** - Are a woman aged 50 years or older - Have had breast-conserving surgery for early-stage invasive breast cancer - Have a tumor smaller than 3 cm with clear surgical margins - Have certain lower-risk cancer features (grade I or II, no lymph node involvement, no lymphovascular invasion) - Are in good health (ECOG 0–1) **You may NOT be eligible if you:** - Have had breast or chest radiation before - Have cancer that has spread elsewhere in the body - Have certain higher-risk tumor features (e.g., the classic invasive lobular type) - Have had a previous cancer (other than certain non-melanoma skin cancers) Talk to your doctor to see if this trial is right for you.