Photons – Radiobiological issues related to the risk of second malignancies |
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| Institution: | 1. Department of Medical Physics, Centre Oscar Lambret and University Lille 1, France;2. Academic Department of Radiation Oncology, Centre Oscar Lambret and University Lille 2, France;1. Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;2. Faculty of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;3. Department of Health Sciences, School of Medicine, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;4. Department of Medical Technology, Kyushu University Hospital, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;5. Saga Heavy Ion Medical Accelerator in Tosu, 415, Harakoga-cho, Tosu 841-0071, Japan;1. German Cancer Research Center (DKFZ), Division of Medical Physics in Radiation Oncology, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany;2. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany;3. Heidelberg University Hospital, Department of Radiation Oncology, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany;4. Advacam s.r.o., Na Balkáně 2075/70, 130 00 Praha 3, Czech Republic;5. Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horská 3a/22, 12800 Prague 2, Czech Republic;1. CELIA, Centre Laser Intenses et Applications, Université de Bordeaux-CNRS-CEA, F-33400 Talence, France;2. Department of Radiotherapy, Institut Bergonié, Comprehensive Cancer Center, F-33076 Bordeaux, France;1. International Atomic Energy Agency, Department of Nuclear Sciences and Applications, Division of Human Health, Dosimetry and Medical Radiation Physics Section, Vienna International Centre, PO Box 100, A-1400 Vienna, Austria;2. Technische Universität München, Klinikum Rechts der Isar, Klinik für Strahlentherapie und Radiologische Onkologie, Ismaninger Str.22, D-81675 Munich, Germany;3. Centers for Disease Control and Prevention, Radiation Studies Branch, Div. of Environmental Hazards and Health Effects, National Center for Environmental Health, 4770 Buford Highway, NE, Atlanta 30341-3717, GA, United States;4. International Atomic Energy Agency, Department of Nuclear Safety and Security, Division of Radiation, Office of the Deputy Director General, Incident and Emergency Centre, Vienna International Centre, PO Box 100, A-1400 Vienna, Austria;5. Medical and Technical Director REAC/TS and Clinical Professor, Department of Therapeutic Radiology, Yale University School of Medicine Radiation Emergency Assistance Center/Training Site, P.O. Box 117, MS 39, Oak Ridge, TN 37831, United States;6. Executive Officer, National Institutes for Quantum and Radiological Science and Technology (QST) 4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba 263-8555, Japan;7. International Atomic Energy Agency, Department of Nuclear Safety and Security, Division of Radiation, Transport and Waste Safety, Radiation Safety and Monitoring Section, Radiation Protection of Patients Unit, Vienna International Centre, PO Box 100, A-1400 Vienna, Austria;8. Department of Radiation Health Management, Fukushima Medical University, Fukushima 960-1295, Japan |
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| Abstract: | Photons are widely used in radiotherapy and while they are low LET radiation, can still pose a risk in developing second malignant neoplasms (SMN). Due to the physics of photons that allow distribution of energy outside the target volume, out-of-field irradiation is an important component of SMN risk assessment. The epidemiological evidence supporting this risk should be augmented with radiobiological justifications for a better understanding of the underlying processes.There are several factors that impact second cancer risk which can be analysed from a radiobiological perspective: age at irradiation, type of irradiated tissue, irradiated volume, treatment technique, previous irradiation/radiological investigations. Age-dependence has a radiobiological foundation given by the higher radiosensitivity of children as compared to adult patients. However, in its 2013 report, UNSCEAR advises against generalisation of the effects of childhood radiation exposure, given the fact that these effects are strongly organ dependent. Furthermore, the age-dependent radiation sensitivity has a bimodal distribution, since aging cells present an increase in the oxidative stress, which can promote premalignant cells.Non-targeted effects such as radiation-induced genomic instability, bystander or abscopal effects could also impact on the risk of SMN. Recent studies show that beside the known cellular changes, bystander effects can be manifested through increased cell proliferation, which could be a culprit for SMN development. Furthermore, new evidence on the existence of tumour-specific cancer stem cells that are long-lived and more quiescent and radioresistant than non-stem cancer cells can raise questions about their association with SMN risk. |
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| Keywords: | Radiotherapy Radiosensitivity Non-targeted effects Cancer stem cells |
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