Dosimetric Comparison of Volumetric Arc Therapy Methods for Stereotactic Body Radiotherapy in Liver Metastasis
Ezgi OYMAK1,Ozan Cem GÜLER2,Cem ÖNAL2
1Department of Radiation Oncology, İskenderun Gelişim Hospital, Hatay-Türkiye
2Department of Radiation Oncology, Başkent University Faculty of Medicine, Adana Research and Treatment Center, Adana-Türkiye
3Department of Radiation Oncology, Başkent University Faculty of Medicine, Ankara-Türkiye
DOI : 10.5505/tjo.2022.3702 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.

Three plans were generated: VMATM was generated with Monaco Treatment Planning System (TPS), VMATE 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.

All plans met the criteria for PTV coverage. Maximum PTV doses were significantly higher in VMATM plan, and minimum PTV doses were significantly lower in VMATE plan. The dose conformity and homogeneity indices of PTV were better in VMATE plan. Only mean bowel maximum dose was significantly higher in HT plan compared to VMATM plan only. The liver Dmean were significantly higher in PTV larger than 50 cm³. Liver Dmean in PTV >50 cm³ was significantly less in VMATM plan compared to HT (p=0.04) and VMATE plans (p=0.04).

All three plans met the criteria for PTV coverage with no significant difference in OARs doses. VMATE plan yielded better homogeneity and conformity in PTV compared to VMATM and HT, and healthy liver tissue was better spared especially in larger tumors (>50 cm³) with VMATE plans. Keywords : Helical tomotherapy; liver metastasis; stereotactic body radiotherapy; volumetric arc therapy