Dosimetric comparison of simultaneous integrated boost with intensity-modulated radiotherapy, volumetric modulated arc therapy, and hybrid intensity-modulated radiotherapy in patients with multiple brain metastases / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the impact of simultaneous integrated boost ( SIB) with different radiotherapy plans on the dosimetry of the target volume and organs at risk ( OAR) in patients with multiple brain metastases ( MBM ) , and to provide a basis for the selection of an optimal clinical radiotherapy. Methods Ten patients with MBM who were treated with whole-brain SIB radiotherapy were randomly selected in this analysis. The local imaging data from the enrolled patients were re-planned with dynamic intensity-modulated radiotherapy ( dynamic IMRT ) , dual-arc volumetric modulated arc therapy ( dual-arc VMAT) , and hybrid-IMRT ( h-IMRT) . h-IMRT plan was created by inversely optimizing 3 and 4 fixed fields of IMRT based on conformal radiotherapy. Two-tailed Wilcoxon matched pairs signed rank sum test was performed to analyze the differences between the three radiotherapy plans in the conformity index ( CI) and homogeneity index (HI) of the planning target volumes (PTV), Dmean and Dmax of OAR, monitor units ( MU) , and delivery time. Results CI of PTVs with VMAT plan was better than that with IMRT and h-IMRT plans (P=004,000), and no significant difference in HI was observed between the three plans( P>005) . There were no significant differences in CI and HI between 3 and 4 fields in dynamic IMRT ( P>005 ) . h-IMRT 3-and 4-field plans had significantly reduced doses to the eye lens and eyeballs than dynamic IMRT and VMAT plans (all P=000), and the three plans had similar doses to the brainstem and optic nerve ( P>005) . As for the MHs and delivery time, dynamic IMRT and VMAT plans showed the highest and lowest value, respectively ( all P= 000 ) . Conclusions All the three plans meet the clinical requirements. VMAT shows the highest treatment efficiency. H-IMRT protects the eye lens and eyeballs more effectively while maintaining the doses to the PTV, with reduced MU compared with IMRT. These offer a reference for designing the radiotherapy plan in MBM patients.