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Koksal Akbas C, Vurro F, Fiorino C, Cozzarini C, Cavaliere F, Milani P, Broggi S, Del Vecchio A, Di Muzio N, Tacchetti C, Enrico Spinelli A. Preclinical photon minibeam radiotherapy using a custom collimator: Dosimetry characterization and preliminary in-vivo results on a glioma model. Phys Med 2024; 124:103420. [PMID: 38970950 DOI: 10.1016/j.ejmp.2024.103420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/28/2024] [Accepted: 06/28/2024] [Indexed: 07/08/2024] Open
Abstract
PURPOSE The purpose of this study is to investigate the dosimetric characteristics of a collimator for minibeam radiotherapy (MBRT) with film dosimetry and Monte Carlo (MC) simulations. The outcome of MBRT with respect to conventional RT using a glioma preclinical model was also evaluated. METHODS A multi-slit collimator was designed to be used with commercial small animal irradiator. The collimator was built by aligning 0.6 mm wide and 5 mm thick parallel lead leaves at 0.4 mm intervals. Dosimetry characteristics were evaluated by Gafchromic (CG) films and TOPAS Monte Carlo (MC) code. An in vivo experiment was performed using a glioma preclinical model by injecting two million GL261cells subcutaneously and treating with 25 Gy, single fraction, with MBRT and conventional RT. Survival curves and acute radiation damage were measured to compare both treatments. RESULTS A satisfactory agreement between experimental results and MC simulations were obtained, the measured FWHM and distance between the peaks were respectively 0.431 and 1.098 mm. In vivo results show that MBRT can provide local tumor control for three weeks after RT treatment and a similar survival fraction of open beam radiotherapy. No severe acute effects were seen for the MBRT group. CONCLUSIONS We developed a minibeam collimator and presented its dosimetric features. Satisfactory agreement between MC and GC films was found with differences consistent with uncertainties due to fabrication and set-up errors. The survival curves of MBRT and open field RT are similar while atoxicity is dramatically lower with MBRT, preliminarily confirming the expected effect.
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Affiliation(s)
- Canan Koksal Akbas
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy; Medical Physics Department, Istanbul University Oncology Institute, Istanbul, Turkey
| | - Federica Vurro
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Claudio Fiorino
- Medical Physics Department, IRCCS San Raffaele Scientific Institute, Milan, Italy.
| | - Cesare Cozzarini
- Radiotherapy Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Paolo Milani
- Department of Physics, University of Milan, Milan, Italy
| | - Sara Broggi
- Medical Physics Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Nadia Di Muzio
- Radiotherapy Department, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Carlo Tacchetti
- Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy
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Eling L, Kefs S, Keshmiri S, Balosso J, Calvet S, Chamel G, Drevon-Gaud R, Flandin I, Gaudin M, Giraud L, Laissue JA, Pellicioli P, Verry C, Adam JF, Serduc R. Neuro-Oncologic Veterinary Trial for the Clinical Transfer of Microbeam Radiation Therapy: Acute to Subacute Radiotolerance after Brain Tumor Irradiation in Pet Dogs. Cancers (Basel) 2024; 16:2701. [PMID: 39123429 PMCID: PMC11311398 DOI: 10.3390/cancers16152701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 07/08/2024] [Accepted: 07/25/2024] [Indexed: 08/12/2024] Open
Abstract
Synchrotron Microbeam Radiation Therapy (MRT) has repeatedly proven its superiority compared with conventional radiotherapy for glioma control in preclinical research. The clinical transfer phase of MRT has recently gained momentum; seven dogs with suspected glioma were treated under clinical conditions to determine the feasibility and safety of MRT. We administered a single fraction of 3D-conformal, image-guided MRT. Ultra-high-dose rate synchrotron X-ray microbeams (50 µm-wide, 400 µm-spaced) were delivered through five conformal irradiation ports. The PTV received ~25 Gy peak dose (within microbeams) per port, corresponding to a minimal cumulated valley dose (diffusing between microbeams) of 2.8 Gy. The dogs underwent clinical and MRI follow-up, and owner evaluations. One dog was lost to follow-up. Clinical exams of the remaining six dogs during the first 3 months did not indicate radiotoxicity induced by MRT. Quality of life improved from 7.3/10 [±0.7] to 8.9/10 [±0.3]. Tumor-induced seizure activity decreased significantly. A significant tumor volume reduction of 69% [±6%] was reached 3 months after MRT. Our study is the first neuro-oncologic veterinary trial of 3D-conformal Synchrotron MRT and reveals that MRT does not induce acute to subacute radiotoxicity in normal brain tissues. MRT improves quality of life and leads to remarkable tumor volume reduction despite low valley dose delivery. This trial is an essential step towards the forthcoming clinical application of MRT against deep-seated human brain tumors.
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Affiliation(s)
- Laura Eling
- Institut National de la Santé et de la Recherche Médicale UA7 Synchrotron Radiation for Biomedicine, Université Grenoble Alpes, 38400 Saint-Martin-d’Hères, France; (S.K.); (J.-F.A.); (R.S.)
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Samy Kefs
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Sarvenaz Keshmiri
- Institut National de la Santé et de la Recherche Médicale UA7 Synchrotron Radiation for Biomedicine, Université Grenoble Alpes, 38400 Saint-Martin-d’Hères, France; (S.K.); (J.-F.A.); (R.S.)
| | - Jacques Balosso
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Susan Calvet
- Argos Clinique Vétérinaire Pierre du Terrail, 38530 Pontcharra, France;
| | - Gabriel Chamel
- Clinical Oncology Unit, Small Animal Internal Medicine Department, University of Lyon, VetAgro Sup Campus Vétérinaire, 69280 Marcy l’Etoile, France;
- Unité de Recherche Interaction Cellules Environnement, University of Lyon, VetAgro Sup Campus Vétérinaire, 69280 Marcy l’Etoile, France
| | | | - Isabelle Flandin
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Maxime Gaudin
- OnlyVet, Centre Hospitalier Vétérinaire, 69800 Saint Priest, France; (M.G.); (L.G.)
| | - Lucile Giraud
- OnlyVet, Centre Hospitalier Vétérinaire, 69800 Saint Priest, France; (M.G.); (L.G.)
| | | | - Paolo Pellicioli
- European Synchrotron Radiation Facility, 38000 Grenoble, France;
| | - Camille Verry
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Jean-François Adam
- Institut National de la Santé et de la Recherche Médicale UA7 Synchrotron Radiation for Biomedicine, Université Grenoble Alpes, 38400 Saint-Martin-d’Hères, France; (S.K.); (J.-F.A.); (R.S.)
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
| | - Raphaël Serduc
- Institut National de la Santé et de la Recherche Médicale UA7 Synchrotron Radiation for Biomedicine, Université Grenoble Alpes, 38400 Saint-Martin-d’Hères, France; (S.K.); (J.-F.A.); (R.S.)
- Centre Hospitalier Universitaire Grenoble Alpes, Maquis du Grésivaudan, 38700 La Tronche, France; (S.K.); (J.B.); (I.F.); (C.V.)
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McMillan MT, Khan AJ, Powell SN, Humm J, Deasy JO, Haimovitz-Friedman A. Spatially Fractionated Radiotherapy in the Era of Immunotherapy. Semin Radiat Oncol 2024; 34:276-283. [PMID: 38880536 DOI: 10.1016/j.semradonc.2024.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Spatially fractionated radiotherapy (SFRT) includes historical grid therapy approaches but more recently encompasses the controlled introduction of one or more cold dose regions using intensity modulation delivery techniques. The driving hypothesis behind SFRT is that it may allow for an increased immune response that is otherwise suppressed by radiation effects. With both two- and three-dimensional SFRT approaches, SFRT dose distributions typically include multiple dose cold spots or valleys. Despite its unconventional methods, reported clinical experience shows that SFRT can sometimes induce marked tumor regressions, even in patients with large hypoxic tumors. Preclinical models using extreme dose distributions (i.e., half-sparing) have been shown to nevertheless result in full tumor eradications, a more robust immune response, and systemic anti-tumor immunity. SFRT takes advantage of the complementary immunomodulatory features of low- and high-dose radiotherapy to integrate the delivery of both into a single target. Clinical trials using three-dimensional SFRT (i.e., lattice-like dose distributions) have reported both promising tumor and toxicity results, and ongoing clinical trials are investigating synergy between SFRT and immunotherapies.
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Affiliation(s)
| | | | | | - John Humm
- Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY
| | - Joseph O Deasy
- Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY
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Prezado Y, Grams M, Jouglar E, Martínez-Rovira I, Ortiz R, Seco J, Chang S. Spatially fractionated radiation therapy: a critical review on current status of clinical and preclinical studies and knowledge gaps. Phys Med Biol 2024; 69:10TR02. [PMID: 38648789 DOI: 10.1088/1361-6560/ad4192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 04/22/2024] [Indexed: 04/25/2024]
Abstract
Spatially fractionated radiation therapy (SFRT) is a therapeutic approach with the potential to disrupt the classical paradigms of conventional radiation therapy. The high spatial dose modulation in SFRT activates distinct radiobiological mechanisms which lead to a remarkable increase in normal tissue tolerances. Several decades of clinical use and numerous preclinical experiments suggest that SFRT has the potential to increase the therapeutic index, especially in bulky and radioresistant tumors. To unleash the full potential of SFRT a deeper understanding of the underlying biology and its relationship with the complex dosimetry of SFRT is needed. This review provides a critical analysis of the field, discussing not only the main clinical and preclinical findings but also analyzing the main knowledge gaps in a holistic way.
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Affiliation(s)
- Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, F-91400, Orsay, France
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, F-91400, Orsay, France
- New Approaches in Radiotherapy Lab, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), Instituto de investigación Sanitaria de Santiago de Compostela (IDIS), University of Santiago de Compostela, Santiago de Compostela, A Coruña, E-15706, Spain
- Oportunius Program, Galician Agency of Innovation (GAIN), Xunta de Galicia, Santiago de Compostela, A Coruña, Spain
| | - Michael Grams
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, United States of America
| | - Emmanuel Jouglar
- Institut Curie, PSL Research University, Department of Radiation Oncology, F-75005, Paris and Orsay Protontherapy Center, F-91400, Orsay, France
| | - Immaculada Martínez-Rovira
- Physics Department, Universitat Auto`noma de Barcelona, E-08193, Cerdanyola del Valle`s (Barcelona), Spain
| | - Ramon Ortiz
- University of California San Francisco, Department of Radiation Oncology, 1600 Divisadero Street, San Francisco, CA 94143, United States of America
| | - Joao Seco
- Division of Biomedical physics in Radiation Oncology, DKFZ-German Cancer Research Center, Heidelberg, Germany
- Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Sha Chang
- Dept of Radiation Oncology and Department of Biomedical Engineering, University of North Carolina School of Medicine, United States of America
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolin State University, United States of America
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Modic Z, Markelc B, Jesenko T. Partial-Volume Irradiation of Murine Tumors. Methods Mol Biol 2024; 2773:97-104. [PMID: 38236540 DOI: 10.1007/978-1-0716-3714-2_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Radiotherapy is a widely used approach for cancer treatment. However, delivering a single high dose of radiation to bulky tumors can be challenging due to the toxicities induced in the surrounding healthy tissue. To overcome this issue, a nonuniform high dose can be delivered using partial-volume tumor irradiation or spatially fractionated radiotherapy (SFRT). Moreover, SFRT has the potential to induce a stronger antitumor immune response compared to traditional radiotherapy due to the preservation of immune cells in the unirradiated tumor regions. There are several SFRT approaches, including GRID therapy, three-dimensional GRID therapy (LATTICE), microbeam radiation therapy (MRT), and Stereotactic Body Radiation Therapy for PArtial Tumor irradiation targeting exclusively the HYpoxic segment (SBRT-PATHY). The following protocol describes partial-volume tumor irradiation, a technique that enables dose delivery to only a part of the tumor in mice using an X-ray generator and collimators of different dimensions that limit the size of the irradiation field.
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Affiliation(s)
- Ziva Modic
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Bostjan Markelc
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia
| | - Tanja Jesenko
- Department of Experimental Oncology, Institute of Oncology Ljubljana, Ljubljana, Slovenia.
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
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Barnes MJ, Afshar N, Cameron M, Hausermann D, Hardcastle N, Lerch M. The design and characterization of a novel dynamic collimator system for synchrotron radiotherapy applications. Med Phys 2023; 50:5806-5816. [PMID: 37531199 DOI: 10.1002/mp.16664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 07/13/2023] [Accepted: 07/21/2023] [Indexed: 08/03/2023] Open
Abstract
BACKGROUND Novel synchrotron radiotherapy techniques are currently limited to using prefabricated beam-limiting blocks for field definition. For large experiments, a single square tungsten block is often used for every treatment since conformal blocks are both patient and field specific, and require long lead times for fabrication. Future synchrotron radiotherapy treatments would benefit from a dynamic collimator system. PURPOSE We developed and tested a novel collimator design for use on the Imaging and Medical Beamline (IMBL) at the ANSTO Australian Synchrotron. METHODS The maximum usable beam size on IMBL is 50-mm wide by 3-mm tall. Given the beam shape, targets must be vertically scanned through the synchrotron beam to cover the target volume. To shape the beam, a novel collimator design was developed, consisting of two semi-circular leaves made from 4-mm thick tungsten sheets, with each leaf capable of both vertical and horizontal movement. A software model was created to optimize motor trajectories and generate deliverable treatment fields. A series of geometric field shapes and clinical target volumes were delivered using the collimator and imaged with a digital imaging detector. Four similarity metrics (volumetric similarity, DICE, and the average and maximum Hausdorff distances) were used to measure differences between the input and planned fields, and the planned and delivered fields. RESULTS Differences between input and planned fields increased with delivery speed, and were worse for rectangular and square fields compared to circular fields. However, the differences between planned and delivered fields were small, where the maximum average deviation between the fields was 0.25 mm (one pixel). Field repeatability was consistent with no difference (σ = 0 for all metrics) observed in consecutively delivered fields. CONCLUSIONS We have successfully built and demonstrated a novel collimator for synchrotron radiotherapy applications on IMBL. Several design improvements have been highlighted and will be addressed in future revisions the collimator. However, in its current state, the collimator enables dynamically delivered conformal treatment fields to be utilized on IMBL, and is ready to support the forthcoming canine treatments on IMBL.
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Affiliation(s)
- Micah J Barnes
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
- ANSTO Australian Synchrotron, Clayton, Victoria, Australia
- Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Nader Afshar
- ANSTO Australian Synchrotron, Clayton, Victoria, Australia
| | | | | | - Nicholas Hardcastle
- Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Michael Lerch
- Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia
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Grams MP, Deufel CL, Kavanaugh JA, Corbin KS, Ahmed SK, Haddock MG, Lester SC, Ma DJ, Petersen IA, Finley RR, Lang KG, Spreiter SS, Park SS, Owen D. Clinical aspects of spatially fractionated radiation therapy treatments. Phys Med 2023; 111:102616. [PMID: 37311338 DOI: 10.1016/j.ejmp.2023.102616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/06/2023] [Accepted: 05/30/2023] [Indexed: 06/15/2023] Open
Abstract
PURPOSE To provide clinical guidance for centers wishing to implement photon spatially fractionated radiation therapy (SFRT) treatments using either a brass grid or volumetric modulated arc therapy (VMAT) lattice approach. METHODS We describe in detail processes which have been developed over the course of a 3-year period during which our institution treated over 240 SFRT cases. The importance of patient selection, along with aspects of simulation, treatment planning, quality assurance, and treatment delivery are discussed. Illustrative examples involving clinical cases are shown, and we discuss safety implications relevant to the heterogeneous dose distributions. RESULTS SFRT can be an effective modality for tumors which are otherwise challenging to manage with conventional radiation therapy techniques or for patients who have limited treatment options. However, SFRT has several aspects which differ drastically from conventional radiation therapy treatments. Therefore, the successful implementation of an SFRT treatment program requires the multidisciplinary expertise and collaboration of physicians, physicists, dosimetrists, and radiation therapists. CONCLUSIONS We have described methods for patient selection, simulation, treatment planning, quality assurance and delivery of clinical SFRT treatments which were built upon our experience treating a large patient population with both a brass grid and VMAT lattice approach. Preclinical research and patient trials aimed at understanding the mechanism of action are needed to elucidate which patients may benefit most from SFRT, and ultimately expand its use.
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Affiliation(s)
- Michael P Grams
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA.
| | - Christopher L Deufel
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - James A Kavanaugh
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Kimberly S Corbin
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Safia K Ahmed
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Michael G Haddock
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Scott C Lester
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Daniel J Ma
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Ivy A Petersen
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Randi R Finley
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Karen G Lang
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Sheri S Spreiter
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Sean S Park
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
| | - Dawn Owen
- Department of Radiation Oncology, Mayo Clinic, 200 First St SW, Rochester, MN 55905, USA
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Baiocco G, Bartzsch S, Conte V, Friedrich T, Jakob B, Tartas A, Villagrasa C, Prise KM. A matter of space: how the spatial heterogeneity in energy deposition determines the biological outcome of radiation exposure. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2022; 61:545-559. [PMID: 36220965 PMCID: PMC9630194 DOI: 10.1007/s00411-022-00989-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 08/03/2022] [Indexed: 05/10/2023]
Abstract
The outcome of the exposure of living organisms to ionizing radiation is determined by the distribution of the associated energy deposition at different spatial scales. Radiation proceeds through ionizations and excitations of hit molecules with an ~ nm spacing. Approaches such as nanodosimetry/microdosimetry and Monte Carlo track-structure simulations have been successfully adopted to investigate radiation quality effects: they allow to explore correlations between the spatial clustering of such energy depositions at the scales of DNA or chromosome domains and their biological consequences at the cellular level. Physical features alone, however, are not enough to assess the entity and complexity of radiation-induced DNA damage: this latter is the result of an interplay between radiation track structure and the spatial architecture of chromatin, and further depends on the chromatin dynamic response, affecting the activation and efficiency of the repair machinery. The heterogeneity of radiation energy depositions at the single-cell level affects the trade-off between cell inactivation and induction of viable mutations and hence influences radiation-induced carcinogenesis. In radiation therapy, where the goal is cancer cell inactivation, the delivery of a homogenous dose to the tumour has been the traditional approach in clinical practice. However, evidence is accumulating that introducing heterogeneity with spatially fractionated beams (mini- and microbeam therapy) can lead to significant advantages, particularly in sparing normal tissues. Such findings cannot be explained in merely physical terms, and their interpretation requires considering the scales at play in the underlying biological mechanisms, suggesting a systemic response to radiation.
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Affiliation(s)
- Giorgio Baiocco
- Radiation Biophysics and Radiobiology Group, Physics Department, University of Pavia, Pavia, Italy.
| | - Stefan Bartzsch
- Institute for Radiation Medicine, Helmholtz Centre Munich, Munich, Germany
- Department of Radiation Oncology, Technical University of Munich, Munich, Germany
| | - Valeria Conte
- Istituto Nazionale Di Fisica Nucleare INFN, Laboratori Nazionali Di Legnaro, Legnaro, Italy
| | - Thomas Friedrich
- Department of Biophysics, GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany
| | - Burkhard Jakob
- Department of Biophysics, GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany
| | - Adrianna Tartas
- Biomedical Physics Division, Institute of Experimental Physics, University of Warsaw, Warsaw, Poland
| | - Carmen Villagrasa
- IRSN, Institut de Radioprotection et de Sûreté Nucléaire, Fontenay aux Roses, France
| | - Kevin M Prise
- Patrick G Johnston Centre for Cancer Research, Queen's University Belfast, Belfast, UK
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Microbeam Radiation Therapy controls local growth of radioresistant melanoma and treats out-of-field locoregional metastasis. Int J Radiat Oncol Biol Phys 2022; 114:478-493. [DOI: 10.1016/j.ijrobp.2022.06.090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/17/2022] [Accepted: 06/24/2022] [Indexed: 11/21/2022]
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10
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Fernandez-Palomo C, Chang S, Prezado Y. Should Peak Dose Be Used to Prescribe Spatially Fractionated Radiation Therapy?-A Review of Preclinical Studies. Cancers (Basel) 2022; 14:cancers14153625. [PMID: 35892895 PMCID: PMC9330631 DOI: 10.3390/cancers14153625] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/20/2022] [Accepted: 07/21/2022] [Indexed: 12/04/2022] Open
Abstract
Spatially fractionated radiotherapy (SFRT) is characterized by the coexistence of multiple hot and cold dose subregions throughout the treatment volume. In preclinical studies using single-fraction treatment, SFRT can achieve a significantly higher therapeutic index than conventional radiotherapy (RT). Published clinical studies of SFRT followed by RT have reported promising results for bulky tumors. Several clinical trials are currently underway to further explore the clinical benefits of SFRT. However, we lack the important understanding of the correlation between dosimetric parameters and treatment response that we have in RT. In this work, we reviewed and analyzed this important correlation from previous preclinical SFRT studies. We reviewed studies prior to 2022 that treated animal-bearing tumors with minibeam radiotherapy (MBRT) or microbeam radiotherapy (MRT). Eighteen studies met our selection criteria. Increased lifespan (ILS) relative to control was used as the treatment response. The preclinical SFRT dosimetric parameters analyzed were peak dose, valley dose, average dose, beam width, and beam spacing. We found that valley dose was the dosimetric parameter with the strongest correlation with ILS (p-value < 0.01). For studies using MRT, average dose and peak dose were also significantly correlated with ILS (p-value < 0.05). This first comprehensive review of preclinical SFRT studies shows that the valley dose (rather than the peak dose) correlates best with treatment outcome (ILS).
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Affiliation(s)
| | - Sha Chang
- Department of Radiation Oncology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7512, USA
- Correspondence:
| | - Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France;
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
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11
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Barnes MJ, Paino J, Day LR, Butler D, Häusermann D, Pelliccia D, Crosbie JC. SyncMRT: a solution to image-guided synchrotron radiotherapy for quality assurance and pre-clinical trials. JOURNAL OF SYNCHROTRON RADIATION 2022; 29:1074-1084. [PMID: 35787575 PMCID: PMC9255576 DOI: 10.1107/s1600577522004829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 05/05/2022] [Indexed: 06/15/2023]
Abstract
In this work, a new image guidance system and protocols for delivering image-guided radiotherapy (IGRT) on the Imaging and Medical Beamline (IMBL) at the ANSTO Australian Synchrotron are introduced. The image guidance methods used and the resulting accuracy of tumour alignment in in vivo experiments are often under-reported. Image guidance tasks are often complex, time-consuming and prone to errors. If unchecked, they may result in potential mis-treatments. We introduce SyncMRT, a software package that provides a simple, image guidance tool-kit for aligning samples to the synchrotron beam. We have demonstrated sub-millimetre alignment using SyncMRT and the small-animal irradiation platform (the DynamicMRT system) on the IMBL. SyncMRT has become the standard for carrying out IGRT treatments on the IMBL and has been used in all pre-clinical radiotherapy experiments since 2017. Further, we introduce two quality assurance (QA) protocols to synchrotron radiotherapy on the IMBL: the Winston-Lutz test and hidden target test. It is shown that the presented QA tests are appropriate for picking up geometrical setup errors and assessing the end-to-end accuracy of the image guidance process. Together, these tools make image guidance easier and provide a mechanism for reporting the geometric accuracy of synchrotron-based IGRT treatments. Importantly, this work is scalable to other delivery systems, and is in continual development to support the upcoming veterinary radiotherapy trials on the IMBL.
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Affiliation(s)
- M. J. Barnes
- ANSTO Australian Synchrotron, Kulin Nation, Clayton, Victoria, Australia
- Peter MacCallum Cancer Centre, Kulin Nation, Melbourne, Victoria, Australia
- School of Science, RMIT Univeristy, Kulin Nation, Melbourne, Victoria, Australia
- Illawarra Health and Medical Research Institute, Dharawal Nation, Wollongong, New South Wales, Australia
| | - J. Paino
- Illawarra Health and Medical Research Institute, Dharawal Nation, Wollongong, New South Wales, Australia
- Centre for Medical Radiation Physics, University of Wollongong, Dharawal Nation, Wollongong, New South Wales, Australia
| | - L. R. Day
- School of Science, RMIT Univeristy, Kulin Nation, Melbourne, Victoria, Australia
| | - D. Butler
- Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Kulin Nation, Yallambie, Victoria, Australia
| | - D. Häusermann
- ANSTO Australian Synchrotron, Kulin Nation, Clayton, Victoria, Australia
| | - D. Pelliccia
- Instruments and Data Tools, Kulin Nation, Melbourne, Victoria, Australia
| | - J. C. Crosbie
- School of Science, RMIT Univeristy, Kulin Nation, Melbourne, Victoria, Australia
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Trappetti V, Fazzari J, Fernandez-Palomo C, Smyth L, Potez M, Shintani N, de Breuyn Dietler B, Martin OA, Djonov V. Targeted Accumulation of Macrophages Induced by Microbeam Irradiation in a Tissue-Dependent Manner. Biomedicines 2022; 10:biomedicines10040735. [PMID: 35453485 PMCID: PMC9025837 DOI: 10.3390/biomedicines10040735] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/08/2022] [Accepted: 03/18/2022] [Indexed: 02/01/2023] Open
Abstract
Radiation therapy (RT) is a vital component of multimodal cancer treatment, and its immunomodulatory effects are a major focus of current therapeutic strategies. Macrophages are some of the first cells recruited to sites of radiation-induced injury where they can aid in tissue repair, propagate radiation-induced fibrogenesis and influence tumour dynamics. Microbeam radiation therapy (MRT) is a unique, spatially fractionated radiation modality that has demonstrated exceptional tumour control and reduction in normal tissue toxicity, including fibrosis. We conducted a morphological analysis of MRT-irradiated normal liver, lung and skin tissues as well as lung and melanoma tumours. MRT induced distinct patterns of DNA damage, reflecting the geometry of the microbeam array. Macrophages infiltrated these regions of peak dose deposition at variable timepoints post-irradiation depending on the tissue type. In normal liver and lung tissue, macrophages clearly demarcated the beam path by 48 h and 7 days post-irradiation, respectively. This was not reflected, however, in normal skin tissue, despite clear DNA damage marking the beam path. Persistent DNA damage was observed in MRT-irradiated lung carcinoma, with an accompanying geometry-specific influx of mixed M1/M2-like macrophage populations. These data indicate the unique potential of MRT as a tool to induce a remarkable accumulation of macrophages in an organ/tissue-specific manner. Further characterization of these macrophage populations is warranted to identify their organ-specific roles in normal tissue sparing and anti-tumour responses.
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Affiliation(s)
- Verdiana Trappetti
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
| | - Jennifer Fazzari
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
| | - Cristian Fernandez-Palomo
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
| | - Lloyd Smyth
- Department of Obstetrics and Gynaecology, Royal Women’s Hospital, University of Melbourne, Melbourne, VIC 3052, Australia;
| | - Marine Potez
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
- Department of Immunology, H. Lee Moffitt Cancer Center and Research Institute, 12902 USF Magnolia Drive, Tampa, FL 33612, USA
| | - Nahoko Shintani
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
| | - Bettina de Breuyn Dietler
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
| | - Olga A. Martin
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
- Division of Radiation Oncology, Peter MacCallum Cancer Centre, 305 Grattan St., Melbourne, VIC 3000, Australia
- Department of Oncology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Valentin Djonov
- Institute of Anatomy, University of Bern, Baltzerstarsse 2, 3012 Bern, Switzerland; (V.T.); (J.F.); (C.F.-P.); (M.P.); (N.S.); (B.d.B.D.); (O.A.M.)
- Correspondence:
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Non-Targeted Effects of Synchrotron Radiation: Lessons from Experiments at the Australian and European Synchrotrons. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12042079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Studies have been conducted at synchrotron facilities in Europe and Australia to explore a variety of applications of synchrotron X-rays in medicine and biology. We discuss the major technical aspects of the synchrotron irradiation setups, paying specific attention to the Australian Synchrotron (AS) and the European Synchrotron Radiation Facility (ESRF) as those best configured for a wide range of biomedical research involving animals and future cancer patients. Due to ultra-high dose rates, treatment doses can be delivered within milliseconds, abiding by FLASH radiotherapy principles. In addition, a homogeneous radiation field can be spatially fractionated into a geometric pattern called microbeam radiotherapy (MRT); a coplanar array of thin beams of microscopic dimensions. Both are clinically promising radiotherapy modalities because they trigger a cascade of biological effects that improve tumor control, while increasing normal tissue tolerance compared to conventional radiation. Synchrotrons can deliver high doses to a very small volume with low beam divergence, thus facilitating the study of non-targeted effects of these novel radiation modalities in both in-vitro and in-vivo models. Non-targeted radiation effects studied at the AS and ESRF include monitoring cell–cell communication after partial irradiation of a cell population (radiation-induced bystander effect, RIBE), the response of tissues outside the irradiated field (radiation-induced abscopal effect, RIAE), and the influence of irradiated animals on non-irradiated ones in close proximity (inter-animal RIBE). Here we provide a summary of these experiments and perspectives on their implications for non-targeted effects in biomedical fields.
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Abstract
AbstractSpatially fractionated radiation therapy (SFRT) challenges some of the classical dogmas in conventional radiotherapy. The highly modulated spatial dose distributions in SFRT have been shown to lead, both in early clinical trials and in small animal experiments, to a significant increase in normal tissue dose tolerances. Tumour control effectiveness is maintained or even enhanced in some configurations as compared with conventional radiotherapy. SFRT seems to activate distinct radiobiological mechanisms, which have been postulated to involve bystander effects, microvascular alterations and/or immunomodulation. Currently, it is unclear which is the dosimetric parameter which correlates the most with both tumour control and normal tissue sparing in SFRT. Additional biological experiments aiming at parametrizing the relationship between the irradiation parameters (beam width, spacing, peak-to-valley dose ratio, peak and valley doses) and the radiobiology are needed. A sound knowledge of the interrelation between the physical parameters in SFRT and the biological response would expand its clinical use, with a higher level of homogenisation in the realisation of clinical trials. This manuscript reviews the state of the art of this promising therapeutic modality, the current radiobiological knowledge and elaborates on future perspectives.
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Price LS, Rivera JN, Madden AJ, Herity LB, Piscitelli JA, Mageau S, Santos CM, Roques JR, Midkiff B, Feinberg NN, Darr D, Chang SX, Zamboni WC. Minibeam radiation therapy enhanced tumor delivery of PEGylated liposomal doxorubicin in a triple-negative breast cancer mouse model. Ther Adv Med Oncol 2021; 13:17588359211053700. [PMID: 34733359 PMCID: PMC8558804 DOI: 10.1177/17588359211053700] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 09/29/2021] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Minibeam radiation therapy is an experimental radiation therapy utilizing an array of parallel submillimeter planar X-ray beams. In preclinical studies, minibeam radiation therapy has been shown to eradicate tumors and cause significantly less damage to normal tissue compared to equivalent radiation doses delivered by conventional broadbeam radiation therapy, where radiation dose is uniformly distributed. METHODS Expanding on prior studies that suggested minibeam radiation therapy increased perfusion in tumors, we compared a single fraction of minibeam radiation therapy (peak dose:valley dose of 28 Gy:2.1 Gy and 100 Gy:7.5 Gy) and broadbeam radiation therapy (7 Gy) in their ability to enhance tumor delivery of PEGylated liposomal doxorubicin and alter the tumor microenvironment in a murine tumor model. Plasma and tumor pharmacokinetic studies of PEGylated liposomal doxorubicin and tumor microenvironment profiling were performed in a genetically engineered mouse model of claudin-low triple-negative breast cancer (T11). RESULTS Minibeam radiation therapy (28 Gy) and broadbeam radiation therapy (7 Gy) increased PEGylated liposomal doxorubicin tumor delivery by 7.1-fold and 2.7-fold, respectively, compared to PEGylated liposomal doxorubicin alone, without altering the plasma disposition. The enhanced tumor delivery of PEGylated liposomal doxorubicin by minibeam radiation therapy is consistent after repeated dosing, is associated with changes in tumor macrophages but not collagen or angiogenesis, and nontoxic to local tissues. Our study indicated that the minibeam radiation therapy's ability to enhance the drug delivery decreases from 28 to 100 Gy peak dose. DISCUSSION Our studies suggest that low-dose minibeam radiation therapy is a safe and effective method to significantly enhance the tumor delivery of nanoparticle agents.
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Affiliation(s)
- Lauren S.L. Price
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA
- Translational Oncology and Nanoparticle Drug Development (TOND2I) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Judith N. Rivera
- Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, USA
| | - Andrew J. Madden
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA
- Translational Oncology and Nanoparticle Drug Development (TOND2I) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Leah B. Herity
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA
- Translational Oncology and Nanoparticle Drug Development (TOND2I) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Joseph A. Piscitelli
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA
- Translational Oncology and Nanoparticle Drug Development (TOND2I) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Savannah Mageau
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, Chapel Hill, NC, USA
- UNC Advanced Translational Pharmacology and Analytical Chemistry (ATPAC) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Charlene M. Santos
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
- The Animal Studies Core, UNC at Chapel Hill, Chapel Hill, NC, USA
| | - Jose R. Roques
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
- The Animal Studies Core, UNC at Chapel Hill, Chapel Hill, NC, USA
| | - Bentley Midkiff
- Translational Pathology Lab, UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
| | - Nana N. Feinberg
- Translational Pathology Lab, UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
| | - David Darr
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
| | - Sha X. Chang
- Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, USA
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
- Department of Radiation Oncology, UNC at Chapel Hill, Chapel Hill, NC, USA
| | - William C. Zamboni
- Division of Pharmacotherapy & Experimental Therapeutics, UNC Eshelman School of Pharmacy, The University of North Carolina at Chapel Hill, 1022B Genetic Medicine Building, 120 Mason Farm Road, Campus Box 7361, Chapel Hill, NC 27599-7361, USA
- Translational Oncology and Nanoparticle Drug Development (TOND2I) Lab, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- UNC Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
- Carolina Center of Cancer Nanotechnology Excellence (C-CCNE), Chapel Hill, NC, USA
- North Carolina Biomedical Innovation Network, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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16
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Bertho A, Ortiz R, Juchaux M, Gilbert C, Lamirault C, Pouzoulet F, Polledo L, Liens A, Warfving N, Sebrie C, Jourdain L, Patriarca A, de Marzi L, Prezado Y. First Evaluation of Temporal and Spatial Fractionation in Proton Minibeam Radiation Therapy of Glioma-Bearing Rats. Cancers (Basel) 2021; 13:cancers13194865. [PMID: 34638352 PMCID: PMC8507607 DOI: 10.3390/cancers13194865] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 01/11/2023] Open
Abstract
Simple Summary Proton minibeam radiation therapy (pMBRT) is a novel therapeutic approach based on a distinct dose delivery method: the dose distributions follow a pattern with regions of peaks (high doses) and valleys (low doses). pMBRT was shown to be able to widen the therapeutic window in glioma-bearing rats. In previous studies the irradiation was performed in one single fraction. The work reported in this manuscript is the first evaluation detailing the response of glioma-bearing rats to a temporal fractionation in proton minibeam radiation therapy, delivered under a crossfire geometry. A significant increase of the median survival time was obtained when the dose was delivered over two sessions as opposed to in a single fraction. This result could facilitate the path towards pMBRT treatments. Abstract (1) Background: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy technique using spatially modulated narrow proton beams. pMBRT results in a significantly reduced local tissue toxicity while maintaining or even increasing the tumor control efficacy as compared to conventional radiotherapy in small animal experiments. In all the experiments performed up to date in tumor bearing animals, the dose was delivered in one single fraction. This is the first assessment on the impact of a temporal fractionation scheme on the response of glioma-bearing animals to pMBRT. (2) Methods: glioma-bearing rats were irradiated with pMBRT using a crossfire geometry. The response of the irradiated animals in one and two fractions was compared. An additional group of animals was also treated with conventional broad beam irradiations. (3) Results: pMBRT delivered in two fractions at the biological equivalent dose corresponding to one fraction resulted in the highest median survival time, with 80% long-term survivors free of tumors. No increase in local toxicity was noted in this group with respect to the other pMBRT irradiated groups. Conventional broad beam irradiations resulted in the most severe local toxicity. (4) Conclusion: Temporal fractionation increases the therapeutic index in pMBRT and could ease the path towards clinical trials.
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Affiliation(s)
- Annaïg Bertho
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France; (A.B.); (R.O.); (M.J.); (C.G.)
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
| | - Ramon Ortiz
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France; (A.B.); (R.O.); (M.J.); (C.G.)
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
| | - Marjorie Juchaux
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France; (A.B.); (R.O.); (M.J.); (C.G.)
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
| | - Cristèle Gilbert
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France; (A.B.); (R.O.); (M.J.); (C.G.)
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
| | - Charlotte Lamirault
- Translational Research Department, Institut Curie, Experimental Radiotherapy Platform, Université Paris Saclay, 91400 Orsay, France; (C.L.); (F.P.)
| | - Frederic Pouzoulet
- Translational Research Department, Institut Curie, Experimental Radiotherapy Platform, Université Paris Saclay, 91400 Orsay, France; (C.L.); (F.P.)
| | - Laura Polledo
- AnaPath GmbH, AnaPath Services, Hammerstrasse 49, 4410 Liestal, Switzerland; (L.P.); (A.L.); (N.W.)
| | - Alethea Liens
- AnaPath GmbH, AnaPath Services, Hammerstrasse 49, 4410 Liestal, Switzerland; (L.P.); (A.L.); (N.W.)
| | - Nils Warfving
- AnaPath GmbH, AnaPath Services, Hammerstrasse 49, 4410 Liestal, Switzerland; (L.P.); (A.L.); (N.W.)
| | - Catherine Sebrie
- CEA, CNRS, Inserm, Service Hospitalier Frédéric Joliot, BIOMAPS Université Paris-Saclay, 91401 Orsay, France; (C.S.); (L.J.)
| | - Laurène Jourdain
- CEA, CNRS, Inserm, Service Hospitalier Frédéric Joliot, BIOMAPS Université Paris-Saclay, 91401 Orsay, France; (C.S.); (L.J.)
| | - Annalisa Patriarca
- Centre de Protonthérapie d’Orsay, Radiation Oncology Department, Campus Universitaire, Institut Curie, PSL Research University, 91898 Orsay, France; (A.P.); (L.d.M.)
| | - Ludovic de Marzi
- Centre de Protonthérapie d’Orsay, Radiation Oncology Department, Campus Universitaire, Institut Curie, PSL Research University, 91898 Orsay, France; (A.P.); (L.d.M.)
- Institut Curie, Campus Universitaire, PSL Research University, University Paris Saclay, INSERM LITO, 91898 Orsay, France
| | - Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France; (A.B.); (R.O.); (M.J.); (C.G.)
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400 Orsay, France
- Correspondence:
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Montay-Gruel P, Corde S, Laissue JA, Bazalova-Carter M. FLASH radiotherapy with photon beams. Med Phys 2021; 49:2055-2067. [PMID: 34519042 DOI: 10.1002/mp.15222] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 08/12/2021] [Accepted: 08/30/2021] [Indexed: 12/16/2022] Open
Abstract
Ultra-high-dose rate "FLASH" radiotherapy (FLASH-RT) has been shown to drastically reduce normal tissue toxicities while being as efficacious as conventional dose rate radiotherapy to treat tumors. A large number of preclinical studies describing this so-called FLASH effect have led to the clinical translation of FLASH-RT using ultra-high-dose rate electron and proton beams. Although the vast majority of radiation therapy treatments are delivered using X-rays, few preclinical data using ultra-high-dose rate X-ray irradiation have been published. This review focuses on different methods that can be used to generate ultra-high-dose rate X-rays and their beam characteristics along with their effect on the biological tissues and the perspectives for the development of FLASH-RT with X-rays.
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Affiliation(s)
- Pierre Montay-Gruel
- Department of Radiation Oncology, University of California, Irvine, California, USA.,Department of Radiotherapy, Iridium Network, Antwerp, Belgium
| | - Stéphanie Corde
- Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW, Australia.,Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW, Australia.,Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - Jean A Laissue
- Institute of Pathology, University of Bern, Bern, Switzerland
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A Brief Overview of the Preclinical and Clinical Radiobiology of Microbeam Radiotherapy. Clin Oncol (R Coll Radiol) 2021; 33:705-712. [PMID: 34454806 DOI: 10.1016/j.clon.2021.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/27/2021] [Accepted: 08/17/2021] [Indexed: 11/23/2022]
Abstract
Microbeam radiotherapy (MRT) is the delivery of spatially fractionated beams that have the potential to offer significant improvements in the therapeutic ratio due to the delivery of micron-sized high dose and dose rate beams. They build on longstanding clinical experience of GRID radiotherapy and more recently lattice-based approaches. Here we briefly overview the preclinical evidence for MRT efficacy and highlight the challenges for bringing this to clinical utility. The biological mechanisms underpinning MRT efficacy are still unclear, but involve vascular, bystander, stem cell and potentially immune responses. There is probably significant overlap in the mechanisms underpinning MRT responses and FLASH radiotherapy that needs to be further defined.
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Trappetti V, Fernandez-Palomo C, Smyth L, Klein M, Haberthür D, Butler D, Barnes M, Shintani N, de Veer M, Laissue JA, Vozenin MC, Djonov V. Synchrotron Microbeam Radiation Therapy for the Treatment of Lung Carcinoma: A Preclinical Study. Int J Radiat Oncol Biol Phys 2021; 111:1276-1288. [PMID: 34364976 DOI: 10.1016/j.ijrobp.2021.07.1717] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 07/07/2021] [Accepted: 07/30/2021] [Indexed: 11/17/2022]
Abstract
PURPOSE In the past 3 decades, synchrotron microbeam radiation therapy (S-MRT) has been shown to achieve both good tumor control and normal tissue sparing in a range of preclinical animal models. However, the use of S-MRT for the treatment of lung tumors has not yet been investigated. This study is the first to evaluate the therapeutic efficacy of S-MRT for the treatment of lung carcinoma, using a new syngeneic and orthotopic mouse model. METHODS AND MATERIALS Lewis Lung carcinoma-bearing mice were irradiated with 2 cross-fired arrays of S-MRT or synchrotron broad-beam (S-BB) radiation therapy. S-MRT consisted of 17 microbeams with a width of 50 µm and center-to-center spacing of 400 µm. Each microbeam delivered a peak entrance dose of 400 Gy whereas S-BB delivered a homogeneous entrance dose of 5.16 Gy (corresponding to the S-MRT valley dose). RESULTS Both treatments prolonged the survival of mice relative to the untreated controls. However, mice in the S-MRT group developed severe pulmonary edema around the irradiated carcinomas and did not have improved survival relative to the S-BB group. Subsequent postmortem examination of tumor size revealed that the mice in the S-MRT group had notably smaller tumor volume compared with the S-BB group, despite the presence of edema. Mice that were sham-implanted did not display any decline in health after S-MRT, experiencing only mild and transient edema between 4 days and 3 months postirradiation which disappeared after 4 months. Finally, a parallel study investigating the lungs of healthy mice showed the complete absence of radiation-induced pulmonary fibrosis 6 months after S-MRT. CONCLUSIONS S-MRT is a promising tool for the treatment of lung carcinoma, reducing tumor size compared with mice treated with S-BB and sparing healthy lungs from pulmonary fibrosis. Future experiments should focus on optimizing S-MRT parameters to minimize pulmonary edema and maximize the therapeutic ratio.
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Affiliation(s)
| | | | - Lloyd Smyth
- Department of Obstetrics and Gynaecology, University of Melbourne, Royal Women's Hospital, Melbourne, Australia
| | - Mitzi Klein
- Imaging and Medical Beamline, Australian Nuclear Science and Technology Organisation, Australian Synchrotron, Clayton, Australia
| | | | - Duncan Butler
- Imaging and Medical Beamline, Australian Nuclear Science and Technology Organisation, Australian Synchrotron, Clayton, Australia
| | - Micah Barnes
- Imaging and Medical Beamline, Australian Nuclear Science and Technology Organisation, Australian Synchrotron, Clayton, Australia; Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia
| | | | - Michael de Veer
- Monash Biomedical Imaging, Monash University, Clayton, Australia
| | | | - Marie C Vozenin
- Department of Radiation Oncology/CHUV, Lausanne University Hospital and University of Lausanne, Switzerland
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20
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Trappetti V, Fazzari JM, Fernandez-Palomo C, Scheidegger M, Volarevic V, Martin OA, Djonov VG. Microbeam Radiotherapy-A Novel Therapeutic Approach to Overcome Radioresistance and Enhance Anti-Tumour Response in Melanoma. Int J Mol Sci 2021; 22:7755. [PMID: 34299373 PMCID: PMC8303317 DOI: 10.3390/ijms22147755] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/15/2021] [Accepted: 07/17/2021] [Indexed: 12/19/2022] Open
Abstract
Melanoma is the deadliest type of skin cancer, due to its invasiveness and limited treatment efficacy. The main therapy for primary melanoma and solitary organ metastases is wide excision. Adjuvant therapy, such as chemotherapy and targeted therapies are mainly used for disseminated disease. Radiotherapy (RT) is a powerful treatment option used in more than 50% of cancer patients, however, conventional RT alone is unable to eradicate melanoma. Its general radioresistance is attributed to overexpression of repair genes in combination with cascades of biochemical repair mechanisms. A novel sophisticated technique based on synchrotron-generated, spatially fractionated RT, called Microbeam Radiation Therapy (MRT), has been shown to overcome these treatment limitations by allowing increased dose delivery. With MRT, a collimator subdivides the homogeneous radiation field into an array of co-planar, high-dose microbeams that are tens of micrometres wide and spaced a few hundred micrometres apart. Different preclinical models demonstrated that MRT has the potential to completely ablate tumours, or significantly improve tumour control while dramatically reducing normal tissue toxicity. Here, we discuss the role of conventional RT-induced immunity and the potential for MRT to enhance local and systemic anti-tumour immune responses. Comparative gene expression analysis from preclinical tumour models indicated a specific gene signature for an 'MRT-induced immune effect'. This focused review highlights the potential of MRT to overcome the inherent radioresistance of melanoma which could be further enhanced for future clinical use with combined treatment strategies, in particular, immunotherapy.
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Affiliation(s)
- Verdiana Trappetti
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
| | - Jennifer M. Fazzari
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
| | - Cristian Fernandez-Palomo
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
| | - Maximilian Scheidegger
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
| | - Vladislav Volarevic
- Department of Genetics, Department of Microbiology and Immunology, Faculty of Medical Sciences, University of Kragujevac, 34000 Kragujevac, Serbia;
| | - Olga A. Martin
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
- Peter MacCallum Cancer Centre, Division of Radiation Oncology, Melbourne, VIC 3000, Australia
- University of Melbourne, Parkville, VIC 3010, Australia
| | - Valentin G. Djonov
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (V.T.); (J.M.F.); (C.F.-P.); (M.S.); (O.A.M.)
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21
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Sabatasso S, Fernandez-Palomo C, Hlushchuk R, Fazzari J, Tschanz S, Pellicioli P, Krisch M, Laissue JA, Djonov V. Transient and Efficient Vascular Permeability Window for Adjuvant Drug Delivery Triggered by Microbeam Radiation. Cancers (Basel) 2021; 13:cancers13092103. [PMID: 33925455 PMCID: PMC8123803 DOI: 10.3390/cancers13092103] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/23/2021] [Accepted: 04/24/2021] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Microbeam Radiation Therapy (MRT) induces a transient vascular permeability window, which offers a novel drug-delivery system for the preferential accumulation of therapeutic compounds in tumors. MRT is a preclinical cancer treatment modality that spatially fractionates synchrotron X-rays into micrometer-wide planar microbeams which can induce transient vascular permeability, especially in the immature tumor vessels, without compromising vascular perfusion. Here, we characterized this phenomenon using Chicken Chorioallantoic Membrane (CAM) and demonstrated its therapeutic potential in human glioblastoma xenografts in mice. METHODS the developing CAM was exposed to planar-microbeams of 75 Gy peak dose with Synchrotron X-rays. Similarly, mice harboring human glioblastoma xenografts were exposed to peak microbeam doses of 150 Gy, followed by treatment with Cisplatin. Tumor progression was documented by Magnetic Resonance Imaging (MRI) and caliper measurements. RESULTS CAM exposed to MRT exhibited vascular permeability, beginning 15 min post-irradiation, reaching its peak from 45 min to 2 h, and ending by 4 h. We have deemed this period the "permeability window". Morphological analysis showed partially fragmented endothelial walls as the cause of the increased transport of FITC-Dextran into the surrounding tissue and the extravasation of 100 nm microspheres (representing the upper range of nanoparticles). In the human glioblastoma xenografts, MRI measurements showed that the combined treatment dramatically reduced the tumor size by 2.75-fold and 5.25-fold, respectively, compared to MRT or Cisplatin alone. CONCLUSIONS MRT provides a novel mechanism for drug delivery by increasing vascular transpermeability while preserving vessel integrity. This permeability window increases the therapeutic index of currently available chemotherapeutics and could be combined with other therapeutic agents such as Nanoparticles/Antibodies/etc.
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Affiliation(s)
- Sara Sabatasso
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Cristian Fernandez-Palomo
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Ruslan Hlushchuk
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Jennifer Fazzari
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Stefan Tschanz
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Paolo Pellicioli
- Biomedical Beamline ID17, European Synchrotron Radiation Facility, 38043 Grenoble, France; (P.P.); (M.K.)
| | - Michael Krisch
- Biomedical Beamline ID17, European Synchrotron Radiation Facility, 38043 Grenoble, France; (P.P.); (M.K.)
| | - Jean A. Laissue
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
| | - Valentin Djonov
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (S.S.); (C.F.-P.); (R.H.); (J.F.); (S.T.); (J.A.L.)
- Correspondence: ; Tel.: +41-31-631-84-32
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22
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Butterworth KT, Williams JP. Animal Models for Radiotherapy Research: All (Animal) Models Are Wrong but Some Are Useful. Cancers (Basel) 2021; 13:cancers13061319. [PMID: 33809414 PMCID: PMC8001499 DOI: 10.3390/cancers13061319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 03/15/2021] [Indexed: 12/16/2022] Open
Affiliation(s)
- Karl T. Butterworth
- Patrick G. Johnston Centre for Cancer Research, Queen’s University Belfast, Belfast BT9 7AE, UK
- Correspondence:
| | - Jacqueline P. Williams
- University of Rochester Medical Centre, University of Rochester, Rochester, NY 14642, USA;
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23
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Forrester HB, Lobachevsky PN, Stevenson AW, Hall CJ, Martin OA, Sprung CN. Abscopal Gene Expression in Response to Synchrotron Radiation Indicates a Role for Immunological and DNA Damage Response Genes. Radiat Res 2021; 194:678-687. [PMID: 32991732 DOI: 10.1667/rade-19-00014.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 08/24/2020] [Indexed: 11/03/2022]
Abstract
Abscopal effects are an important aspect of targeted radiation therapy due to their implication in normal tissue toxicity from chronic inflammatory responses and mutagenesis. Gene expression can be used to determine abscopal effects at the molecular level. Synchrotron microbeam radiation therapy utilizing high-intensity X rays collimated into planar microbeams is a promising cancer treatment due to its reported ability to ablate tumors with less damage to normal tissues compared to conventional broadbeam radiation therapy techniques. The low scatter of synchrotron radiation enables microbeams to be delivered to tissue effectively, and is also advantageous for out-of-field studies because there is minimal interference from scatter. Mouse legs were irradiated at a dose rate of 49 Gy/s and skin samples in the out-of-field areas were collected. The out-of-field skin showed an increase in Tnf expression and a decrease in Mdm2 expression, genes associated with inflammation and DNA damage. These expression effects from microbeam exposure were similar to those found with broadbeam exposure. In immune-deficient Ccl2 knockout mice, we identified a different gene expression profile which showed an early increase in Mdm2, Tgfb1, Tnf and Ccl22 expression in out-of-field skin that was not observed in the immune-proficient mice. Our results suggest that the innate immune system is involved in out-of-field tissue responses and alterations in the immune response may not eliminate abscopal effects, but could change them.
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Affiliation(s)
- Helen B Forrester
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Australia.,Monash University, Clayton, Australia.,School of Science, RMIT University, Melbourne, Australia
| | - Pavel N Lobachevsky
- Research Division, Peter MacCallum Cancer Centre, Melbourne, Australia.,Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Australia.,Advanced Analytical Technologies, Melbourne, Australia
| | - Andrew W Stevenson
- Australian Synchrotron, ANSTO, Clayton, Australia.,CSIRO Manufacturing, Clayton, Australia
| | | | - Olga A Martin
- Division of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia.,Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Australia
| | - Carl N Sprung
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton, Australia.,Monash University, Clayton, Australia
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24
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Fernandez-Palomo C, Fazzari J, Trappetti V, Smyth L, Janka H, Laissue J, Djonov V. Erratum: Fernandez-Palomo, C., et al. Animal Models in Microbeam Radiation Therapy: A Scoping Review. Cancers 2020, 12, 527. Cancers (Basel) 2020; 12:cancers12113174. [PMID: 33138341 PMCID: PMC7694102 DOI: 10.3390/cancers12113174] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 10/27/2020] [Indexed: 11/25/2022] Open
Affiliation(s)
| | - Jennifer Fazzari
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (C.F.-P.); (J.F.); (V.T.); (J.L.)
| | - Verdiana Trappetti
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (C.F.-P.); (J.F.); (V.T.); (J.L.)
| | - Lloyd Smyth
- Department of Obstetrics & Gynaecology, University of Melbourne, 3057 Parkville, Australia;
| | - Heidrun Janka
- Medical Library, University Library Bern, University of Bern, 3012 Bern, Switzerland;
| | - Jean Laissue
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (C.F.-P.); (J.F.); (V.T.); (J.L.)
| | - Valentin Djonov
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland; (C.F.-P.); (J.F.); (V.T.); (J.L.)
- Correspondence: ; Tel.: +41-31-631-8432
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25
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Complete Remission of Mouse Melanoma after Temporally Fractionated Microbeam Radiotherapy. Cancers (Basel) 2020; 12:cancers12092656. [PMID: 32957691 PMCID: PMC7563854 DOI: 10.3390/cancers12092656] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/10/2020] [Accepted: 09/15/2020] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Synchrotron Microbeam Radiotherapy (MRT) significantly improves local tumour control with minimal normal tissue toxicity. MRT delivers orthovoltage X-rays at an ultra-high "FLASH" dose rate in spatially fractionated beams, typically only few tens of micrometres wide. One of the biggest challenges in translating MRT to the clinic is its use of high peak doses, of around 300-600 Gy, which can currently only be delivered by synchrotron facilities. Therefore, in an effort to improve the translation of MRT to the clinic, this work studied whether the temporal fractionation of traditional MRT into several sessions with lower, more clinically feasible, peak doses could still maintain local tumour control. METHODS Two groups of twelve C57Bl/6J female mice harbouring B16-F10 melanomas in their ears were treated with microbeams of 50 µm in width spaced by 200 µm from their centres. The treatment modality was either (i) a single MRT session of 401.23 Gy peak dose (7.40 Gy valley dose, i.e., dose between beams), or (ii) three MRT sessions of 133.41 Gy peak dose (2.46 Gy valley dose) delivered over 3 days in different anatomical planes, which intersected at 45 degrees. The mean dose rate was 12,750 Gy/s, with exposure times between 34.2 and 11.4 ms, respectively. RESULTS Temporally fractionated MRT ablated 50% of B16-F10 mouse melanomas, preventing organ metastases and local tumour recurrence for 18 months. In the rest of the animals, the median survival increased by 2.5-fold in comparison to the single MRT session and by 4.1-fold with respect to untreated mice. CONCLUSIONS Temporally fractionating MRT with lower peak doses not only maintained tumour control, but also increased the efficacy of this technique. These results demonstrate that the solution to making MRT more clinically feasible is to irradiate with several fractions of intersecting arrays with lower peak doses. This provides alternatives to synchrotron sources where future microbeam radiotherapy could be delivered with less intense radiation sources.
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