Following Patients for More than a Decade: The NCI-supported National Surgical Adjuvant Breast and Bowel Project (NSAABP), now part of NRG Oncology, led the US phase 3 trial. NSABP researchers randomly assigned 4,216 patients with breast cancer who had recently received a lumpectomy to treatment with APBI or WBI. Of this group, 25% had ductal carcinoma in situ (DCIS), 65% had stage 1 breast cancer, and 10% had stage 2 breast cancer. Eighty-one percent of the patients had hormone receptor-positive cancer, and 61% of the patients were postmenopausal. Women assigned to APBI received either brachytherapy (an internal form of radiation therapy) or three-dimensional conformal external beam radiation therapy (3D-CRT). After a median follow-up of 10.2 years, 161 patients had a breast cancer recurrence: 90 patients who received APBI and 71 who received WBI. There were modest differences between the groups in terms of side effects.