Dosimetric Comparison of Breast Irradiation Techniques

Abstract

This study aims to evaluate and compare the dosimetric performance of four advanced radiotherapy techniques: volumetric modulated arc therapy (VMAT), intensity modulated radiotherapy (IMRT), and two hybrid techniques (3-D conformal radiotherapy (3D-CRT) combined with 2 or 5 IMRT beams) in the treatment of breast cancer. The focus is on achieving optimal target coverage while minimising radiation exposure to organs at risk (OARs), including the heart, lungs, and contralateral breast, for both chest wall and intact breast irradiation scenarios. Four treatment plans were developed for each patient using the Varian Eclipse treatment planning system (v18.0), with a prescribed dose of 50 Gy in 25 fractions. Dosimetric comparisons were made to assess the homogeneity index (HI), conformity index (CI), and dose to OARs. Dose-volume histograms (DVHs) were used to assess the doses received by OARs, in line with RTOG-1305 and ICRU Report 83 guidelines. Monitor units (MU’s) and estimated delivery times were also recorded to evaluate the complexities associated with each technique. Key findings indicate that while VMAT achieved the best dose conformity, as evidenced by the lowest conformity index (CI) values of 1.063 ± 0.034 for chestwall and 1.018 ± 0.036 for intact brerast, the Hybrid (5 IMRT beams) technique offered superior dose homogeneity across both treatment scenarios (0.071 ± 0.017 for chestwall and 0.065 ± 0.011 for intact breast). Furthermore, the Hybrid (2IMRT beams) approach was notable for its ability to spare critical organs, particularly the contralateral breast, heart, and lungs. Treatment times varied among the techniques, with Hybrid (2 IMRT Beams) being the technique with the fewest monitor units for chest wall cases (729.0 ± 80.7) and VMAT having the fewest MU for intact breast cases (410.1 ± 53.6), while IMRT was found to be the technique with the most monitor units (MU) in both scenarios. This research underscores the need for tailored radiotherapy planning that considers individual patient factors, clinical risks, and stringent patient-specific quality assurance (PSQA) practices to ensure accurate dose delivery.