The RTOG addressed this issue with trial 9804, designed to study radiation versus none after wide local excision, in patients specifically in the low-risk group. For the trial, this low-risk group was defined as women with unicentric disease found by mammogram only, or those incidentally found at surgery, of low or intermediate nuclear grade, and with necrosis in less than one-third of the ducts examined. Size was 2.5 cm or less, as defined on imaging if possible, and minimal margin width for trial entry was 3 mm. Patients were stratified by age, size of lesion, and final margin width (ie, 3-9 mm, 10 mm or more, or negative reexcision). Tamoxifen for 5 years was prescribed for all women in the original version, but made optional several years into the study.