Patient setup and target definition
tumor, breast, nipple, esophagus, and skin, Visual tumor, breast swelling
TUMOR
Patients were immobilized using the standard breast setup on the breast board in the supine position. A non‐contrast planning CT scan with 3 mm slice thickness (SOMATOM.go CT simulator, Malvern, Pennsylvania, USA) was obtained. The 3D CT scan was brought into Eclipse treatment planning system (TPS, Version 15.6; Varian Medical Systems, Palo Alto, California, USA). Visual tumor was contoured as gross tumor volume (GTV). The clinical target volume (CTV) included the GTV plus an approximate 1.5 cm margin extending from 5 mm below the skin surface to the deep fascia encompassing the post‐surgical skin flaps and underlying soft tissues to the deep fascia; both excluded underlying muscle and rib cage. The planning target volume (PTV) includes a typical margin of 5–10 mm around the CTV to accommodate the daily patient setup error, breast swelling, and breathing motion. The mean PTV volume was 806 ± 687 cc (ranged, 289−2060 cc). The relevant organs‐at‐risk (OAR) that were delineated per Fast‐Forward trial included ipsilateral and contralateral lungs, spinal cord, heart, contralateral breast, nipple, esophagus, and skin.