Multiple randomized studies were performed in the United States as well as around the world verifying this observation.
Similar work is ongoing for a less aggressive form of breast cancer.
This cancer is called intraductal carcinoma or ductal carcinoma in situ. Because of the increasing use of mammograms, small lesions like many intraductal cancers, unpalpable to fingers, are being increasingly detected. This study was nicknamed the B-17 study. In the breast intraductal cancer study, patients were randomly allocated to have either breast radiation or no radiation after lumpectomy. In the early years of the study, women had an axillary lymph node dissection.