Analysis of a volumetric-modulated arc therapy (VMAT) single phase prostate template as a class solution

Abstract

Aim: To assess a class solution template for volumetric-modulated arc therapy (VMAT) for prostate cancer using plan analysis software.Background: VMAT is a development of intensity-modulated radiotherapy (IMRT) with potential advantages for the delivery of radiotherapy (RT) in prostate cancer. Class solutions are increasingly used for facilitating RT planning. Plan analysis software provides an objective tool for evaluating class solutions. Materials and methods:The class solution for VMAT was based on the current static field IMRT template. The plans of 77 prostate cancer patients were evaluated using a set of in-house plan quality metrics (scores) (PlanIQ TM , Sun Nuclear Corporation). The metrics compared the class solution for VMAT planning with the IMRT template and the delivered clinical plan (CP). Eight metrics were associated with target coverage and ten with organs-at-risk (OAR). Individual metrics were summed and the combined scores were subjected to nonparametric analysis. The low-dose wash for both static IMRT and VMAT plans were evaluated using 40 Gy and 25 Gy isodose volumes.Results: VMAT plans were of equal or better quality than the IMRT template and CP for target coverage (combined score) and OAR combined score. The 40 Gy isodose volume was marginally higher with VMAT than IMRT (4.9%) but lower than CP (−6.6%)(P = 0.0074).The 25 Gy volume was significantly lower with VMAT than both IMRT (−32.7%) and CP (−34.4%)(P < 0.00001).Conclusions: Automated VMAT planning for prostate cancer is feasible and the plans are equal to or better than the current IMRT class solution and the delivered clinical plan.

Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

“…VMAT plans were generated using a 6 MV photon beam, with the clinical Monaco Version 5.11.01 TPS (Elekta AB, Stockholm, Sweden) and the Agility MLC. For all patients included in this study a VMAT plan using two coplanar arcs was calculated using a Monte Carlo algorithm, with a calculation grid size of (0.3 cm) 3 and a statistical uncertainty during dose prediction of 1%. These plans were delivered clinically.…”

“…The low-field MR-linac system generates a 6 MV flattening-filter-free (FFF) photon beam in the presence of a 0.35 T magnetic field, using the RayZR MLC, a double-stacked and double-focused 138-leaf MLC with 4.15 mm effective leaf-width at isocentre. The dose calculation algorithm is also based on Monte Carlo simulation, with a calculation grid size of (0.3 cm) 3 and a statistical uncertainty during dose prediction of 1%.…”

Analysis of prostate intensity‐ and volumetric‐modulated arc radiation therapy planning quality with PlanIQTM

“…“Impossible DVH (red)” is defined as the DVH generated using the minimum dose that an off‐target voxel must receive given 100% target coverage. Studies that used the PlanIQ TM software have reported improvements in the treatment plan quality 8–13 . Recently, PlanIQ TM was integrated into Autoplan®, which is implemented in Pinnacle and has been clinically applied 9,10 .…”

Automated planning through robust templates and multicriterial optimization for lung VMAT SBRT of lung lesions

“…Some work has been done in developing class solutions for the treatment of prostate with IMRT, 11,13 even in case of particularly challenging anatomical situations, as in the case of bilateral hip prostheses, 14 and VMAT, for both conventional fractionation 15,16 and SBRT. 17,18 These studies demonstrated automated planning for prostate cancer is feasible and can produce plans that are at least as good as manual plans.…”

“…Moreover, the development of class solutions allows for the "bias-free" comparison between different techniques by applying the previously established templates. 15 Class solutions have been used for technique comparison in breast treatment, 19,20 while a five-field IMRT template was established and evaluated on 40 patients treated with accelerated partial breast irradiation for left and right lesions. 21 The developed template was demonstrated to produce highly conformal and consistent treatment plans.…”