Cargando…

Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors

PURPOSE: During radiation therapy for pediatric brain tumors, the brainstem is a critical organ at risk, possibly with different radio-sensitivity across its substructures. In proton therapy, treatment planning is currently performed using a constant relative biological effectiveness (RBE) of 1.1 (R...

Descripción completa

Detalles Bibliográficos
Autores principales: Fjæra, Lars Fredrik, Indelicato, Daniel J., Ytre-Hauge, Kristian S., Muren, Ludvig P., Lassen-Ramshad, Yasmin, Toussaint, Laura, Dahl, Olav, Stokkevåg, Camilla H.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7811129/
https://www.ncbi.nlm.nih.gov/pubmed/33490724
http://dx.doi.org/10.1016/j.adro.2020.08.008
_version_ 1783637437930536960
author Fjæra, Lars Fredrik
Indelicato, Daniel J.
Ytre-Hauge, Kristian S.
Muren, Ludvig P.
Lassen-Ramshad, Yasmin
Toussaint, Laura
Dahl, Olav
Stokkevåg, Camilla H.
author_facet Fjæra, Lars Fredrik
Indelicato, Daniel J.
Ytre-Hauge, Kristian S.
Muren, Ludvig P.
Lassen-Ramshad, Yasmin
Toussaint, Laura
Dahl, Olav
Stokkevåg, Camilla H.
author_sort Fjæra, Lars Fredrik
collection PubMed
description PURPOSE: During radiation therapy for pediatric brain tumors, the brainstem is a critical organ at risk, possibly with different radio-sensitivity across its substructures. In proton therapy, treatment planning is currently performed using a constant relative biological effectiveness (RBE) of 1.1 (RBE(1.1)), whereas preclinical studies point toward spatial variability of this factor. To shed light on this biological uncertainty, we investigated the spatial agreement between isodose maps produced by different RBE models, with emphasis on (smaller) substructures of the brainstem. METHODS AND MATERIALS: Proton plans were recalculated using Monte Carlo simulations in 3 anonymized pediatric patients with brain tumors (a craniopharyngioma, a low-grade glioma, and a posterior fossa ependymoma) to obtain dose and linear energy transfer distributions. Doses and volume metrics for the brainstem and its substructures were calculated using a constant RBE(1.1), 4 phenomenological RBE models with varying (α/β)(x) parameters, and with a simpler linear energy transfer-dependent model. The spatial agreement between the dose distributions of constant RBE(1.1) versus the variable RBE models was compared using the Dice similarity coefficient. RESULTS: The spatial agreement between the variable RBE dose distributions and RBE(1.1) decreased with increasing isodose levels in all patient cases. The patient with ependymoma showed the greatest variation in dose and dose volumes, where V(50Gy(RBE)) in the brainstem increased from 32% (RBE(1.1)) to 35% to 49% depending on the applied model, corresponding to a spatial agreement (Dice similarity coefficient) between 0.79 and 0.95. The remaining patients showed similar trends, however, with lower absolute values due to lower brainstem doses. CONCLUSIONS: All phenomenological RBE models fully enclosed the isodose volumes of the constant RBE(1.1), and the volumes based on variable RBE spatially agreed. The spatial agreement was dependent on the isodose level, where higher isodose levels showed larger expansions and less agreement between the variable RBE models and RBE(1.1).
format Online
Article
Text
id pubmed-7811129
institution National Center for Biotechnology Information
language English
publishDate 2020
publisher Elsevier
record_format MEDLINE/PubMed
spelling pubmed-78111292021-01-22 Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors Fjæra, Lars Fredrik Indelicato, Daniel J. Ytre-Hauge, Kristian S. Muren, Ludvig P. Lassen-Ramshad, Yasmin Toussaint, Laura Dahl, Olav Stokkevåg, Camilla H. Adv Radiat Oncol Scientific Article PURPOSE: During radiation therapy for pediatric brain tumors, the brainstem is a critical organ at risk, possibly with different radio-sensitivity across its substructures. In proton therapy, treatment planning is currently performed using a constant relative biological effectiveness (RBE) of 1.1 (RBE(1.1)), whereas preclinical studies point toward spatial variability of this factor. To shed light on this biological uncertainty, we investigated the spatial agreement between isodose maps produced by different RBE models, with emphasis on (smaller) substructures of the brainstem. METHODS AND MATERIALS: Proton plans were recalculated using Monte Carlo simulations in 3 anonymized pediatric patients with brain tumors (a craniopharyngioma, a low-grade glioma, and a posterior fossa ependymoma) to obtain dose and linear energy transfer distributions. Doses and volume metrics for the brainstem and its substructures were calculated using a constant RBE(1.1), 4 phenomenological RBE models with varying (α/β)(x) parameters, and with a simpler linear energy transfer-dependent model. The spatial agreement between the dose distributions of constant RBE(1.1) versus the variable RBE models was compared using the Dice similarity coefficient. RESULTS: The spatial agreement between the variable RBE dose distributions and RBE(1.1) decreased with increasing isodose levels in all patient cases. The patient with ependymoma showed the greatest variation in dose and dose volumes, where V(50Gy(RBE)) in the brainstem increased from 32% (RBE(1.1)) to 35% to 49% depending on the applied model, corresponding to a spatial agreement (Dice similarity coefficient) between 0.79 and 0.95. The remaining patients showed similar trends, however, with lower absolute values due to lower brainstem doses. CONCLUSIONS: All phenomenological RBE models fully enclosed the isodose volumes of the constant RBE(1.1), and the volumes based on variable RBE spatially agreed. The spatial agreement was dependent on the isodose level, where higher isodose levels showed larger expansions and less agreement between the variable RBE models and RBE(1.1). Elsevier 2020-08-28 /pmc/articles/PMC7811129/ /pubmed/33490724 http://dx.doi.org/10.1016/j.adro.2020.08.008 Text en © 2020 The Author(s) http://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Scientific Article
Fjæra, Lars Fredrik
Indelicato, Daniel J.
Ytre-Hauge, Kristian S.
Muren, Ludvig P.
Lassen-Ramshad, Yasmin
Toussaint, Laura
Dahl, Olav
Stokkevåg, Camilla H.
Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title_full Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title_fullStr Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title_full_unstemmed Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title_short Spatial Agreement of Brainstem Dose Distributions Depending on Biological Model in Proton Therapy for Pediatric Brain Tumors
title_sort spatial agreement of brainstem dose distributions depending on biological model in proton therapy for pediatric brain tumors
topic Scientific Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7811129/
https://www.ncbi.nlm.nih.gov/pubmed/33490724
http://dx.doi.org/10.1016/j.adro.2020.08.008
work_keys_str_mv AT fjæralarsfredrik spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT indelicatodanielj spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT ytrehaugekristians spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT murenludvigp spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT lassenramshadyasmin spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT toussaintlaura spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT dahlolav spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors
AT stokkevagcamillah spatialagreementofbrainstemdosedistributionsdependingonbiologicalmodelinprotontherapyforpediatricbraintumors