Normal Tissue Response of Combined Temporal and Spatial Fractionation in Proton Minibeam Radiation Therapy.

Autor:	Sammer M; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Dombrowsky AC; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany; Department of Radiation Oncology, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, München, Germany. Electronic address: annique.dombrowsky@helmholtz-muenchen.de., Schauer J; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Oleksenko K; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany., Bicher S; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany; Department of Radiation Oncology, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, München, Germany., Schwarz B; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Rudigkeit S; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Matejka N; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Reindl J; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Bartzsch S; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany; Department of Radiation Oncology, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, München, Germany., Blutke A; Research Unit Analytical Pathology, Helmholtz Zentrum München GmbH, Neuherberg, Germany., Feuchtinger A; Research Unit Analytical Pathology, Helmholtz Zentrum München GmbH, Neuherberg, Germany., Combs SE; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany; Department of Radiation Oncology, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, München, Germany., Dollinger G; Institute for Applied Physics and Metrology, Universität der Bundeswehr München, Neubiberg, Germany., Schmid TE; Institute of Radiation Medicine, Helmholtz Zentrum München GmbH, Neuherberg, Germany; Department of Radiation Oncology, Technical University of Munich, School of Medicine, Klinikum rechts der Isar, München, Germany.
Jazyk:	angličtina
Zdroj:	International journal of radiation oncology, biology, physics [Int J Radiat Oncol Biol Phys] 2021 Jan 01; Vol. 109 (1), pp. 76-83. Date of Electronic Publication: 2020 Aug 14.
DOI:	10.1016/j.ijrobp.2020.08.027
Abstrakt:	Purpose: Proton minibeam radiation therapy, a spatial fractionation concept, widens the therapeutic window. By reducing normal tissue toxicities, it allows a temporally fractionated regime with high daily doses. However, an array shift between daily fractions can affect the tissue-sparing effect by decreasing the total peak-to-valley dose ratio. Therefore, combining temporal fractions with spatial fractionation raises questions about the impact of daily applied dose modulations, reirradiation accuracies, and total dose modulations. Methods and Materials: Healthy mouse ear pinnae were irradiated with 4 daily fractions of 30 Gy mean dose, applying proton pencil minibeams (pMB) of Gaussian σ = 222 μm in 3 different schemes: a 16 pMB array with a center-to-center distance of 1.8 mm irradiated the same position in all sessions (FS1) or was shifted by 0.9 mm to never hit the previously irradiated tissue in each session (FS2), or a 64 pMB array with a center-to-center distance of 0.9 mm irradiated the same position in all sessions (FS3), resulting in the same total dose distribution as FS2. Reirradiation positioning and its accuracy were obtained from image guidance using the unique vessel structure of ears. Acute toxicities (swelling, erythema, and desquamation) were evaluated for 153 days after the first fraction. Late toxicities (fibrous tissue, inflammation) were analyzed on day 153. Results: Reirradiation of highly dose-modulated arrays at a positioning accuracy of 110 ± 52 μm induced the least severe acute and late toxicities. A shift of the same array in FS2 led to significantly inducted acute toxicities, a higher otitis score, and a slight increase in fibrous tissue. FS3 led to the strongest increase in acute and late toxicities. Conclusions: The highest normal-tissue sparing is achieved after accurate reirradiation of a highly dose modulated pMB array, although high positioning accuracies are challenging in a clinical environment. Nevertheless, the same integral dose applied in highly dose-modulated fractions is superior to low daily dose-modulated fractions. (Copyright © 2020. Published by Elsevier Inc.)
Databáze:	MEDLINE
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