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High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak

Proton therapy is a type of hadron radiotherapy used for treating solid tumors. Unlike heavy charged elements, proton radiation is considered to be low LET (Linear Energy Transfer) radiation, like X-rays. However, the clinical SOBP (Spread Out Bragg Peak) proton radiation is considered to be higher...

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Autores principales: Horendeck, Dakota, Walsh, Kade D., Hirakawa, Hirokazu, Fujimori, Akira, Kitamura, Hisashi, Kato, Takamitsu A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8222778/
https://www.ncbi.nlm.nih.gov/pubmed/34178687
http://dx.doi.org/10.3389/fonc.2021.690042
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author Horendeck, Dakota
Walsh, Kade D.
Hirakawa, Hirokazu
Fujimori, Akira
Kitamura, Hisashi
Kato, Takamitsu A.
author_facet Horendeck, Dakota
Walsh, Kade D.
Hirakawa, Hirokazu
Fujimori, Akira
Kitamura, Hisashi
Kato, Takamitsu A.
author_sort Horendeck, Dakota
collection PubMed
description Proton therapy is a type of hadron radiotherapy used for treating solid tumors. Unlike heavy charged elements, proton radiation is considered to be low LET (Linear Energy Transfer) radiation, like X-rays. However, the clinical SOBP (Spread Out Bragg Peak) proton radiation is considered to be higher in relative biological effectiveness (RBE) than both X-ray and their own entrance region. The RBE is estimated to be 1.1–1.2, which can be attributed to the higher LET at the SOBP region than at the entrance region. In order to clarify the nature of higher LET near the Bragg peak of proton radiation and its potential cytotoxic effects, we utilized a horizontal irradiation system with CHO cells. Additionally, we examined DNA repair mutants, analyzed cytotoxicity with colony formation, and assessed DNA damage and its repair with γ-H2AX foci assay in a high-resolution microscopic scale analysis along with the Bragg peak. Besides confirming that the most cytotoxic effects occurred at the Bragg peak, extended cytotoxicity was observed a few millimeters after the Bragg peak. γ-H2AX foci numbers reached a maximum at the Bragg peak and reduced dramatically after the Bragg peak. However, in the post-Bragg peak region, particle track-like structures were sporadically observed. This region contains foci that are more difficult to repair. The peak and post-Bragg peak regions contain rare high LET-like radiation tracks and can cause cellular lethality. This may have caused unwanted side effects and complexities of outputs for the proton therapy treatment.
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spelling pubmed-82227782021-06-25 High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak Horendeck, Dakota Walsh, Kade D. Hirakawa, Hirokazu Fujimori, Akira Kitamura, Hisashi Kato, Takamitsu A. Front Oncol Oncology Proton therapy is a type of hadron radiotherapy used for treating solid tumors. Unlike heavy charged elements, proton radiation is considered to be low LET (Linear Energy Transfer) radiation, like X-rays. However, the clinical SOBP (Spread Out Bragg Peak) proton radiation is considered to be higher in relative biological effectiveness (RBE) than both X-ray and their own entrance region. The RBE is estimated to be 1.1–1.2, which can be attributed to the higher LET at the SOBP region than at the entrance region. In order to clarify the nature of higher LET near the Bragg peak of proton radiation and its potential cytotoxic effects, we utilized a horizontal irradiation system with CHO cells. Additionally, we examined DNA repair mutants, analyzed cytotoxicity with colony formation, and assessed DNA damage and its repair with γ-H2AX foci assay in a high-resolution microscopic scale analysis along with the Bragg peak. Besides confirming that the most cytotoxic effects occurred at the Bragg peak, extended cytotoxicity was observed a few millimeters after the Bragg peak. γ-H2AX foci numbers reached a maximum at the Bragg peak and reduced dramatically after the Bragg peak. However, in the post-Bragg peak region, particle track-like structures were sporadically observed. This region contains foci that are more difficult to repair. The peak and post-Bragg peak regions contain rare high LET-like radiation tracks and can cause cellular lethality. This may have caused unwanted side effects and complexities of outputs for the proton therapy treatment. Frontiers Media S.A. 2021-06-10 /pmc/articles/PMC8222778/ /pubmed/34178687 http://dx.doi.org/10.3389/fonc.2021.690042 Text en Copyright © 2021 Horendeck, Walsh, Hirakawa, Fujimori, Kitamura and Kato https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Oncology
Horendeck, Dakota
Walsh, Kade D.
Hirakawa, Hirokazu
Fujimori, Akira
Kitamura, Hisashi
Kato, Takamitsu A.
High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title_full High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title_fullStr High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title_full_unstemmed High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title_short High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak
title_sort high let-like radiation tracks at the distal side of accelerated proton bragg peak
topic Oncology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8222778/
https://www.ncbi.nlm.nih.gov/pubmed/34178687
http://dx.doi.org/10.3389/fonc.2021.690042
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