Evaluating the benefit of PBS vs. VMAT dose distributions in terms of dosimetric sparing and robustness against inter-fraction anatomical changes for pediatric abdominal tumors

Filipa Guerreiro; Cornel Zachiu; Enrica Seravalli; Cássia O Ribeiro; Geert O Janssens; Mario Ries; Baudouin Denis de Senneville; John H Maduro; Charlotte L Brouwer; Erik W Korevaar; Antje C Knopf; Bas W Raaymakers

doi:10.1016/j.radonc.2019.06.025

Evaluating the benefit of PBS vs. VMAT dose distributions in terms of dosimetric sparing and robustness against inter-fraction anatomical changes for pediatric abdominal tumors

Radiother Oncol. 2019 Sep:138:158-165. doi: 10.1016/j.radonc.2019.06.025. Epub 2019 Jul 11.

Authors

Affiliations

¹ Department of Radiotherapy, University Medical Center Utrecht, The Netherlands. Electronic address: F.Guerreiro@umcutrecht.nl.
² Department of Radiotherapy, University Medical Center Utrecht, The Netherlands. Electronic address: C.Zachiu@umcutrecht.nl.
³ Department of Radiotherapy, University Medical Center Utrecht, The Netherlands. Electronic address: E.Seravalli@umcutrecht.nl.
⁴ Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: c.oraboni.ribeiro@umcg.nl.
⁵ Department of Radiation Oncology, University Medical Center Utrecht, The Netherlands; Princess Máxima Center for Paediatric Oncology, Utrecht, The Netherlands. Electronic address: G.O.R.Janssens@umcutrecht.nl.
⁶ Imaging Division, University Medical Center Utrecht, The Netherlands. Electronic address: M.Ries@umcutrecht.nl.
⁷ Imaging Division, University Medical Center Utrecht, The Netherlands; Institut de Mathématiques de Bordeaux, University of Bordeaux, France. Electronic address: b.desenneville@umcutrecht.nl.
⁸ Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: j.h.maduro@umcg.nl.
⁹ Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: c.l.brouwer@umcg.nl.
¹⁰ Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: e.w.korevaar@umcg.nl.
¹¹ Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: a.c.knopf@umcg.nl.
¹² Department of Radiotherapy, University Medical Center Utrecht, The Netherlands. Electronic address: b.w.raaymakers@umcutrecht.nl.

PMID: 31302390
DOI: 10.1016/j.radonc.2019.06.025

Abstract

Background and purpose: To evaluate the dosimetric sparing and robustness against inter-fraction anatomical changes between photon and proton dose distributions for children with abdominal tumors.

Material and methods: Volumetric modulated arc therapy (VMAT) and intensity-modulated pencil beam scanning (PBS) proton dose distributions were calculated for 20 abdominal pediatric cases (average 3, range 1-8 years). VMAT plans were based on a full-arc while PBS plans on 2-3 posterior-oblique irradiation fields. Plans were robustly optimized on a patient-specific internal target volume (ITV) using a uniform 5 mm set-up uncertainty. Additionally, for the PBS plans a ± 3% proton range uncertainty was accounted for. Fractional dose re-calculations were performed using the planning computed tomography (CT) deformably registered to the daily cone-beam CT (CBCT) images. Fractional doses were accumulated rigidly. Planned and CBCT accumulated VMAT and PBS dose distributions were compared using dose-volume histogram (DVH) parameters.

Results: Significant better sparing of the organs at risk with a maximum reduction in the mean dose of 40% was achieved with PBS. Mean ITV DVH parameters differences between planned and CBCT accumulated dose distributions were smaller than 0.5% for both VMAT and PBS. However, the ITV coverage (V_95% > 99%) was not reached for one patient for the accumulated VMAT dose distribution.

Conclusions: For pediatric patients with abdominal tumors, improved dosimetric sparing was obtained with PBS compared to VMAT. In addition, PBS delivered by posterior-oblique irradiation fields demonstrated to be robust against anatomical inter-fraction changes. Compared to PBS, daily anatomical changes proved to affect the target coverage of VMAT dose distributions to a higher extent.

Keywords: Inter-fraction anatomical changes; Pediatric IGRT; Pediatric abdominal tumors; Proton therapy; Robust pencil beam scanning; VMAT.

Publication types

Comparative Study
Evaluation Study

MeSH terms

Abdominal Neoplasms / diagnostic imaging
Abdominal Neoplasms / pathology
Abdominal Neoplasms / radiotherapy*
Child
Child, Preschool
Cone-Beam Computed Tomography
Humans
Infant
Proton Therapy / methods*
Radiotherapy Dosage
Radiotherapy, Intensity-Modulated / methods*