Potential benefit of MRI-guided IMRT for flank irradiation in pediatric patients with Wilms’ tumor

F. Guerreiro, E. Seravalli, G. O. Janssens, M. M. van den Heuvel-Eibrink, J. J.W. Lagendijk, B. W. Raaymakers

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Purpose/Objective: Flank irradiation for Wilms' tumor (WT) is currently performed at our institute using a cone-beam computed tomography-guided volumetric modulated arc (VMAT CBCT ) workflow. By adding real-time magnetic resonance imaging (MRI) guidance to the treatment, safety margins could be reduced. The study purpose was to quantify the potential reduction of the planning target volume (PTV) margin and its dosimetric impact when using an MRI-guided intensity modulated radiation therapy (IMRT MRI ) workflow compared to the VMAT CBCT workflow. Material/Methods: 4D-CT, MRI and CBCT scans acquired during preparation and treatment of 15 patients, were used to estimate both geometric, motion and patient set-up systematic (∑) and random (σ) errors for VMAT CBCT and IMRT MRI workflows. The mean PTV (PTV mean ) expansion was calculated using the van Herk formula. Treatment plans were generated using five margin scenarios (PTV mean ± 0, 1 and 2 mm). Furthermore, the IMRT MRI plans were optimized with a 1.5T transverse magnetic field turned-on to realistically model an MRI-guided treatment. Plans were evaluated using dose-volume statistics (p<.01, Wilcoxon). Results: Analysis of ∑ and σ errors resulted in a PTV mean of 5 mm for the VMAT CBCT and 3 mm for the IMRT MRI workflows in each orthogonal direction. Target coverage was unaffected by the margin decrease with a mean V 95% =100% for all margin scenarios. For the PTV mean , an average reduction of the mean dose to the organs at risk (OARs) was achieved with IMRT MRI compared to VMAT CBCT : 3.4 ± 2.4% (p<.01) for the kidney, 3.4 ± 2.1% (p<.01) for the liver, 2.8 ± 3.0% (p<.01) for the spleen and 4.9 ± 3.8% (p<.01) for the pancreas, respectively. Conclusions: Imaging data in children with WT demonstrated that the PTV margin could be reduced isotropically down to 2 mm when using the IMRT MRI compared to the VMAT CBCT workflow. The former results in a dose reduction to the OARs while maintaining target coverage.

Original languageEnglish
Pages (from-to)243-250
Number of pages8
JournalActa Oncologica
Volume58
Issue number2
DOIs
Publication statusPublished - 1 Feb 2019

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