Comparison of various radiotherapy techniques in breast cancer with inclusion of internal mammary nodes by through thermoluminescent dosimetry inside the RANDO phantom

Abstract

Introduction: In the various techniques of breast cancer radiotherapy, the presence of the internal mammary nodes (IMNs) in the target volume is important to select the most appropriate technique. This study aimed to compare three radiotherapy techniques with the inclusion of IMNs regarding the dose homogeneity index (DHI) of regional lymph nodes, chest wall, and the dose received by the heart and left lung.Material and Methods: Three techniques were planned on the CT images of the RANDO phantom including wide tangent (WT) contained two opposed tangential 6 MV photon beams, oblique parasternal photon (OPP) and oblique parasternal electron (OPE) that included two opposed tangential 6 MV photon beams with an anterior oblique 6 MV photon beam and an anterior oblique 15 MeV electron beam added to two tangential beams, respectively. The doses reached to the contoured organs were compared in three techniques by using data gathered from the thermoluminescent dosimetry and treatment planning system.Results: The OPE technique caused a lower absorbed dose for the left IMNs than the other two techniques. For the OPP technique, the dose received by the left lung was higher than the tolerance, and the lung dose in the OPE is slightly lower than the WT technique. The absorbed dose by the heart was lowest for the WT technique and the DHI for this technique was better than the other two techniques.Conclusion: The WT technique showed better results regarding the IMNs and chest wall dose homogeneity distribution and the organ at risk protection.