A dosimetric comparison of 3D DCAT vs VMAT for palliative and early-stage liver lesions using eclipse TPS

Volumetric modulated arc therapy (VMAT) and 3D dynamic conformal arc therapy (DCAT) are 2 methods proven useful for the clinical implementation of stereotactic body radiation therapy (SBRT) for lung lesions however, similar comparisons of SBRT liver lesions are lacking. The purpose of this study was to determine if the conformity of dose, irradiated volume, and dose to organs at risk (OAR) are equivalent or improved with the use of DCAT as an alternative treatment method when compared to standard VMAT for SBRT delivery of palliative and early-stage liver lesions. Twenty patients with liver lesions sized 2.0 to 5.0 cm were selected for this study. Plans were created with both DCAT and VMAT techniques for each patient. Metrics evaluated included the mean heart, kidney, large bowel, small bowel, esophagus, and stomach doses, the lung volume receiving 20 Gy (V₂₀), the volume of the normal liver receiving 15 Gy (V₁₅), conformity index (CI), heterogeneity index (HI), and the irradiated volume or volume receiving 25 Gy (V₂₅). The p-values for the mean dose to kidneys, small bowel, esophagus, and the lung V₂₀ were greater than 0.05, and no statistical difference could be determined between DCAT and VMAT. The p-values for the mean heart, large bowel, stomach, and liver V₁₅ were less than 0.05, indicating statistical significance and superiority of VMAT for minimizing dose to these organs, especially V₁₅ of the liver. The DCAT technique produced CI greater than 1.0 for all patients proving superior coverage, while standard VMAT produced significantly improved V₂₅ with p-values less than 0.0001, and consequently higher HI.