The Influence of Treatment Position (Prone vs. Supine) on Whole Breast Target

Objective To investigate the difference of target volumes and dosimetric parameters between supine and prone positions for whole breast irradiation after conserving surgery. Methods Breast cancer patients with T1-2N0M0 stage who underwent radiation therapy after conserving surgery were enrolled. Supine and Prone scan sets were acquired during free breathing for all patients. Target volumes and organs at risk (OARs) including heart, ipsilateral lung and bilateral breast were contoured by the same radiation oncologist. The tumor bed (TB) was determined based on surgical clips. The Clinical target volume (CTV)consisted of the whole breast. The planning target volume (PTV) was CTV plus 0.5cm. The boost of PTV (PTVboost) was TB plus 0.5cm. Dosimetric parameters of target volumes and OARs were compared between supine and prone position.