Comparison of Radiotherapy Techniques in Breast Cancer with Inclusion of Internal Mammary Nodes through Thermoluminescent Dosimetry in a RANDO Phantom

Abstract

Introduction: In various radiotherapy techniques for breast cancer, the inclusion of internal mammary nodes (IMNs) in the target volume is important for selecting 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 and the chest wall, besides the dose received by the heart and the left lung. Material and Methods: Three radiotherapy techniques were planned for CT imaging of the RANDO phantom, including the wide tangent (WT); oblique parasternal photon (OPP); and oblique parasternal electron (OPE) techniques. The doses reaching the contoured organs were compared between the three techniques, using the data gathered from the thermoluminescent dosimetry and treatment planning system. Results: The OPE technique produced a lower absorbed dose for the left IMNs, compared to the other two techniques. In the OPP technique, the dose received by the left lung was higher than its tolerance, while the lung dose in the OPE technique was slightly lower than the WT technique. The absorbed dose by the heart was the lowest in the WT technique; also, the DHI value was better for this technique than the other two techniques. Conclusion: The WT technique showed better results regarding the dose homogeneity distribution of IMNs and the chest wall, as well as protection of organs at risk.

Keywords

• breast cancer
• lymph nodes
• radiotherapy
• rando phantom
• thermoluminescent dosimetry