Volumetric modulated arc therapy (VMAT) is superior to intensity modulated radiotherapy (IMRT) for liver sparing in SBRT for hepatocellular carcinoma

Abstract

Background: The best delivery modality of stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) from a technical point of view is still a matter of debate. The purpose of this study was to compare planning parameters with volumetric modulated arc therapy (VMAT) to static intensity modulated radiotherapy (IMRT) in treatment of HCC treated with SBRT. Methods: Twenty patients (pts) with localized HCC who were treated with SBRT were re-planned using two different radiation techniques: IMRT and VMAT. Patients with Child A cirrhosis received 45-54 Gy in 3 fractions and 5 pts with Child B cirrhosis received 30 Gy in 5 fractions. Planning was optimized to minimize doses to organs at risk (OAR) without compromising coverage of the planning treatment volume (PTV). VMAT and IMRT plans were compared using the conformity index (CI), homogeneity index of the PTV and monitor units (MUs) for time of treatment delivery, and other dose volume histogram (DVH) metrics.Results: The CI of VMAT plans were superior to those of IMRT(1.11±0.05 vs 1.18±0.06 (p <0.05) The MUs were significantly lower for VMAT (423.78±50.65) than for IMRT (890±160.68) (p <0.01). Stomach max dose, normal liver V15 Gy, normal liver mean dose were also decreased with VMAT planning. This was achieved without increased :V30 Gy of duodenum and small bowel , 10 cc(Gy) of duodenum, mean dose of right kidney and cord max dose . Conclusion: PTV coverage was more conformal with VMAT planning, with lower MUs and shorter delivery time compared to IMRT in all pts. Moreover VMAT planning was more effective than IMRT planning in the sparing of normal liver and stomach.