Dosimetric Comparison of 3D Tangential Radiotherapy of Post-Lumpectomy Breast at Two Different Energies

Introduction: Radiation therapy following breast conserving surgery is one of the most common procedures performed in any radiation oncology department. A tangential parallel-opposed pair is almost always the technique of choice for this purpose. This technique is often performed based on 3D treatment planning. The aim of this study was to compare 3D treatment planning for two different energies (Cobalt 60 versus 6 MV photon beams) in tangential irradiation of breast conserving radiotherapy. In this comparison, homogeneity of isodoses within the breast volume and dose received by lungs were considered. Materials and Methods: In this study, twenty patients with breast cancer treated with conservative surgery were included. A CT scan was performed on selected patients. Three-dimensional treatment planning with 6 MV photon beams was carried out for patients on the  Eclipse 3D treatment planning system (TPS). The volumes receiving lower than 95% (Vol105) (hot areas) of the reference dose, and the volume of lung receiving ≥30Gy (Vol≥30Gy) were derived from dose volume histograms (DVHs). Dose homogeneity index was calculated as: DHI = 100 – (Vol>105 + Vol