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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

Guerreiro, F., Zachiu, C., Seravalli, E., Ribeiro, C. O., Janssens, G. O., Ries, M., de Senneville, B. D., Maduro, J. H., Brouwer, C. L., Korevaar, E. W., Knopf, A. C. & Raaymakers, B. W., Sep-2019, In : Radiotherapy and Oncology. 138, p. 158-165 8 p.

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  • 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

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  • 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

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DOI

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. (C) 2019 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)158-165
Number of pages8
JournalRadiotherapy and Oncology
Volume138
Publication statusPublished - Sep-2019

    Keywords

  • Pediatric IGRT, Pediatric abdominal tumors, Robust pencil beam scanning, Proton therapy, VMAT, Inter-fraction anatomical changes, MODULATED PROTON THERAPY, TREATMENT UNCERTAINTIES, WILMS-TUMOR, OPEN-LABEL, RADIOTHERAPY, OPTIMIZATION, PHOTON, CANCER, REGISTRATION, SENSITIVITY

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