The Prone Breast Radiation Therapy Trial

All participants will receive an adjuvant XRT dose to the breast of 50Gy in 25 fractions using an IMRT technique. In both arms, boost to the surgical bed using a mini-tangent technique will be delivered at the treating oncologist's discretion. Acceptable boost doses are 1600cGy/8 fractions, 1000cGy/5 fractions or 1325cGy/25 fractions as a simulatenous integrated boost. Participants randomized to the supine arm will be positioned supine on an angled breast board, with the ipsilateral arm abducted over her head. Participants randomized to the prone arm will be positioned prone on a prone breast board with both arms immobilized above the participant's head. The us of a cushion-like VaclocTM device is permitted at the treating physician's discretion. Radiation beams will be shaped to encompass the breast volume requiring treatment in both arms.