Position and radiation planning
tumor
TUMOR
All patients were immobilized on a breast bracket (CIVCO Medical Solutions, Orange City, IA, USA) for CT simulation in the supine position. The outline of the ipsilateral breast was marked with a lead wire by physical examination before the CT scan. A treatment planning CT scan was performed with 5.0 mm thickness slices from the Atlas (C1) to the second lumbar vertebra (L2) level to cover the whole breast using a 16-slice CT scanner (GE Discovery RT, GE Healthcare, Chicago, IL, USA).The clinical target volume (CTV) was defined as the whole breast according to the marked outline and the fascia of the pectoralis major. The tumor bed target volume for the boost was determined according to surgical changes and silver clips. The planning target volume (PTV) boost and PTV were formed by extending a 5.0 mm margin from CTV and CTV boost, respectively, within 5.0 mm inside of the body outline. Patients who had more than 4 positive axillary nodes or one to three positive nodes with risk factors received additional supra/infraclavicular nodal irradiation. The radiation dose was delivered by intensity modulation radiation therapy with tangential beams. PTV was given 50 Gy in 25 fractions. PTVboost was given 60 Gy in 25 or 30 fractions.One attending radiation oncologist (L.M.) marked lead wire on CT images using the Deepwise Research Platform (Deepwise Inc., Beijing, China, 