Dosimetric evaluation of volumetric modulated arc therapy with simultaneous integrated boost hypofractionated radiation based on two types of multileaf collimators for prostate cancer.

Abstract

For localized prostatic adenocarcinoma, hypo fractionated radiation has been shown to minimize treatment times while producing results that are similar to those of conventionally fractionated radiotherapy; therefore, volumetric modulated arc therapy (VMAT) plans face a real challenge in achieving the dosimetric parameters for planning target volumes (PTVs) and organs at risk (OARs).The aim of this study was to compare the plan quality and dosimetric effects of two different types of multi-leaf collimators (MLCs) on simultaneous integrated boost (SIB) hypo fractionated prostate cancer treatment using VMAT. Using the VMAT procedure, ten patients with prostate cancer were re-planned with two separate MLCs. For each patient, two treatment plans were carried out. The dose volume histogram (DVH) for PTVs and OARs, as well as the conformity index (CI) and homogeneity index (HI) with 5mm vs. 10mm MLC width, were used to examine the dosimetric parameters. The prescribed doses for the prostate gland (PTVp) and the pelvic nodes (PTVn) are 60 Gy/20fractions and 44 Gy/20fractions, respectively. In plans for Agility to MLCi2, HI and CI were improved. For Agility MLC, the p-values for HI and CI were 0.017 and 0.008, respectively. When compared to MLCi2, the dose distribution for PTVs was improved with Agility MLC. When compared to MLCi2, the delivery time with Agility MLC was reduced by 31%. With Agility MLC, the smallest leaf width results in a dosimetric benefit for PTV.