Abstract
PurposeTo analyze the differences between the intensity-modulated radiotherapy (IMRT), single/partial-arc volumetric modulated arc therapy (SA/PA-VMAT) techniques in treatment planning for locally advanced lung cancer.Materials and methods12 patients were retrospectively studied. In each patient's case, several parameters were analyzed based on the dose-volume histograms (DVH) of the IMRT, SA/PA-VMAT plans respectively. Also, each plan was delivered to a phantom for time comparison.ResultsThe SA-VMAT plans showed the superior target dose coverage, although the minimum/mean/maximum doses to the target were similar. For the total and contralateral lungs, the higher V5/10, lower V20/30 and mean lung dose (MLD) were observed in the SA/PA-VMAT plans (p < 0.05, respectively). The PA-VMAT technique improves the dose sparing (V20, V30 and MLD) of the controlateral lung more notably, comparing to those parameters of the IMRT and SA-VMAT plans respectively. The delivered monitor units (MUs) and treatment times were reduced significantly with VMAT plans, especially PA-VMAT plans (for MUs: mean 458.3 vs. 439.2 vs. 435.7 MUs, p < 0.05 and for treatment time: mean 13.7 vs. 10.6 vs. 6.4 minutes, p < 0.01).ConclusionsThe SA-VMAT technique achieves highly conformal dose distribution to the target. Comparing to the IMRT plans, the higher V5/10, lower V20/30 and MLD were observed in the total and contralateral lungs in the VMAT plans, especially in the PA-VMAT plans. The SA/PA-VMAT plans also reduced treatment time with more efficient dose delivering. But the clinical benefit of the VMAT technique for locally advanced lung cancer needs further investigations.
Highlights
VMAT is a new form of intensity-modulated radiotherapy (IMRT), which allows irradiation with the simultaneously changing gantry position, dose rate and multileaf-collimator (MLC) position [1]
Lower dose irradiated to the larger volume of the total lungs were observed in SA/PA-VMAT plans, respectively
The maximum, minimum and average dose of the planning target volume (PTV) are similar between IMRT and SA/PA-VMAT plans respectively, with no statistical significance (p > 0.05)
Summary
VMAT is a new form of IMRT, which allows irradiation with the simultaneously changing gantry position, dose rate and multileaf-collimator (MLC) position [1]. A few studies investigated the clinical and dosimetric advantages of the VMAT technique in treatment for lung cancer presently. Bedford et al reported the first lung cancer case treated with VMAT [2]. Scorsetti et al reported the acute toxicity, initial outcome results and planning parameters of 24 patients with the large-volume non-small cell lung cancer (NSCLC) treated with VMAT, while no dosimetric comparison was described [3]. Holt’s team found that a coplanar VMAT for SBRT for early-stage lung cancer achieved a plan quality and skin dose levels better than those coplanar IMRT plans and reduced treatment time at most by 70% [6]. No dosimetric evaluation had been reported between IMRT and VMAT for locally advanced lung cancer yet
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