Dosimetric Comparison of Volumetric Arc Therapy Methods for Stereotactic Body Radiotherapy in Liver Metastasis

Abstract

OBJECTIVE Volumetric arc therapy (VMAT) is advantageous for stereotactic body radiotherapy (SBRT) delivery; however, it is still unknown which rotational method is optimal for the treatment of liver metastases. This study aims to compare the dosimetric data of SBRT plans with VMAT techniques and helical tomotherapy (HT) in 18 liver metastasis patients. METHODS Three plans were generated: VMAT(M) was generated with Monaco Treatment Planning System (TPS), VMAT(E) with an Eclipse TPS, and HT plans were generated using a Hi-Art Tomotherapy system. The prescribed dose was 54 Gy delivered in three fractions. The planning target volume (PTV) doses and organs at risk (OAR) doses were compared between three plans. RESULTS All plans met the criteria for PTV coverage. Maximum PTV doses were significantly higher in VMAT(M) plan, and minimum PTV doses were significantly lower in VMAT(E )plan. The dose conformity and ho-mogeneity indices of PTV were better in VMAT(E) plan. Only mean bowel maximum dose was significantly higher in HT plan compared to VMAT(M) plan only. The liver D-mean were significantly higher in PTV larger than 50 cm3. Liver D-mean in PTV > 50 cm(3) was significantly less in VMAT(M )plan compared to HT (p=0.04) and VMAT(E) plans (p=0.04). CONCLUSION All three plans met the criteria for PTV coverage with no significant difference in OARs doses. VMAT(E) plan yielded better homogeneity and conformity in PTV compared to VMAT(M) and HT, and healthy liver tissue was better spared especially in larger tumors (> 50 cm(3)) with VMAT(E) plans.