- Arm I: Patients undergo standard whole-breast radiotherapy (WBI) comprising intensity-modulated radiation therapy (IMRT) or three-dimensional conformal radiotherapy (3D-CRT) 5 days a week for 3-5 weeks followed by a sequential radiotherapy boost to the lumpectomy area 5 days a week for 1-1½ weeks. Treatment continues in the absence of disease progression or unacceptable toxicity.