A physicochemical model of reaction kinetics supports peroxyl radical recombination as the main determinant of the FLASH effect.
Radiother Oncol
; 153: 303-310, 2020 12.
Article
em En
| MEDLINE
| ID: mdl-32534957
ABSTRACT
BACKGROUND AND PURPOSE:
FLASH radiotherapy, a technique based on delivering large doses in a single fraction at the micro/millisecond timescale, spares normal tissues from late radiation-induced toxicity, in an oxygen-dependent process, whilst keeping full anti-tumor efficiency. We present a theoretical model taking into account the kinetics of formation and decay of reactive oxygen species, in particular of organic peroxyl radicals ROO. formed by addition of O2 to primary carbon-centred radicals R. and known to play a major role at the origin radio-induced complications. MATERIALS ANDMETHODS:
The model focuses on the time-dependent evolution of radiolytic products in living matter exposed to continuous irradiation at dose-rates in the range 10-3-107Gy·s-1. The 9 differential rate equations resulting from the radiolytic and enzymatic reactions network were solved using the published values of these reactions rate constants in a cellular environment.RESULTS:
The model suggests a correlation between the area-under-the-curve of time-evolving [ROO.] and the probability of normal tissue complications. The model does not lend weight to the hypothesis of transient oxygen depletion as a main determinant of FLASH but rather suggests a major role of radical-radical recombination.CONCLUSION:
The model gives support to the reduction of ROO. lifetime as the main root of FLASH and compares favorably with published experimental results. We conclude that any process - in this case radical recombination - that shortens the lifetime or limits the radiolytic yield of ROO. is likely to protect normoxic tissues against the deleterious effects of radiation.Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Peróxidos
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
Radiother Oncol
Ano de publicação:
2020
Tipo de documento:
Article