Comparison of HyperArc, IMRT, and VMAT plans for Graves’ ophthalmopathy radiotherapy

Abstract

Abstract Objective To compare the dosimetric parameters of three different radiotherapy techniques, HyperArc (HA), volumetric modulated arc therapy (VMAT), and intensity-modulated radiotherapy (IMRT), for patients with Graves’ ophthalmopathy (GO), and to provide guidance for the clinical choice of radiotherapy methods for GO. Materials and Methods Eight patients with GO were enrolled in this study. HA, IMRT, and VMAT plans were generated for each patient. The dosimetric parameters of the target and the organs at risk (OARs) were compared and analyzed among the three plans. Results Compared with VMAT and IMRT plans, the HA plan had a higher conformity index (CI) (HA vs. VMAT, p = 0.012; HA vs. IMRT, p = 0.012) and homogeneity index (HI) (HA vs. VMAT, p = 0.042; HA vs. IMRT, p = 0.012), a lower gradient index (GI) (HA vs. VMAT, p = 0.012; HA vs. IMRT, p = 0.012) and a lower dose to the optic chiasm (HA vs. VMAT, p = 0.012; HA vs. IMRT, p = 0.012) and the brainstem maximum dose (HA vs. VMAT, p = 0.025; HA vs. IMRT, p = 0.017). The dose to lenses and the brain were similar to those in VMAT and IMRT plans (p > 0.05). The dose to the eyeballs slightly increased (left eye: HA vs. VMAT, p = 0.036; HA vs. IMRT, p = 0.012. Right eye: HA vs. VMAT, p = 0.012; HA vs. IMRT, p = 0.012). The machine unit (MU) of the HA plan is the lowest among the three plans. Conclusion For radiotherapy of GO, HA, IMRT, and VMAT are all feasible techniques. Compared with IMRT and VMAT, HA has better target coverage and conformity, homogeneity, and dose gradient, as well as better sparing of critical OARs, while saving treatment time. HA can be considered as the preferred technique for radiotherapy of GO.