Volumetric-modulated arc therapy versus intensity-modulated radiotherapy on the left-sided chest wall and locoregional nodes irradiation in treating postmastectomy breast cancer patients: A comparative dosimetric analysis

Abstract

Purpose: This study was aimed to compare the suitable treatment plan for left-sided chest wall, regional node irradiation by the intensity-modulated radiotherapy (IMRT), and volumetric-modulated arc therapy (VMAT).Materials and Methods: Fifteen patients' computed tomography data set was import into the treatment planning system (Oncentra). Two plans were generated for each patient, the first one using the VMAT technique with two partial arcs and the second one using the IMRT technique with seven coplaner radiation portals using 3D Oncentra TPS with 6 MV photons, step and shoot treatment delivery technique with 80 leaf multileaf collimator, and 1 cm leaf width at the isocenter. The VMAT plans optimized using the collapsed cone (GPU) algorithm and IMRT plans optimized using a collapsed cone algorithm. A hypofractionated prescription dose of 40 Gy/15# was used. The VMAT and IMRT plans compared for Planning Target Volume (PTV) target coverage, homogeneity index (HI), conformity index (CI), and monitor units (MUs) were evaluated. The Organ At Risk (OAR) doses also compared.Results: A comparable PTV coverage (V95%) and mean PTV doses were observed between VMAT and IMRT plans. The PTV maximum dose was higher within IMRT than the VMAT. We observed a better HI for VMAT plans. For conformity index (CI) both plan showed no significant difference. MU values of VMAT are higher than the IMRT treatment in this study. However, VMAT plans show significantly better right lung, heart, and larynx sparing when compared to the IMRT plans. No significant difference was observed in both groups of plan for the right breast and spinal cord. The maximum dose for the left humerus head was compared for both groups of plans.Conclusions: VMAT is dosimetrically superior to the IMRT for irradiation of left-sided chest wall and regional nodes patients in terms of target coverage and OAR sparing.