activity of the medical staff, fostering the weakening of certain control barriers. Furthermore, the increase in complex treatments with several locations to treat and situations of prior radiotherapy history should lead the centres to question the robustness of the safety barriers for these situations. Moreover, the WG on lessons learned by radiotherapy professionals led by ASN has worked on the development of new sheets entitled “treatment safety”. The first two sheets detailing good practices to apply to avoid ESRs relating to identity monitoring and laterality errors shall be published in the first quarter of 2025. The number of ESRs in radiotherapy has been dropping continually and significantly since 2015 (see point 2.7, Graph 14 page 242), and by about 13% since 2021. If this drop can attributed in part to a better control of the risks (application of strict quality assurance procedures, complete dematerialisation with lists of “record and verify” tasks, harmonisation of medical protocols, contour delineation assistance software, automatic application of dosimetry shifts, monitoring of preparation times, etc.), the ASN inspectors observe, as in 2023, a reduction in the number of adverse events registered and analysed internally and fewer meetings of the experience feedback committees. The root causes of these events are still not sufficiently investigated and the lessons learned from the events notified at national level are poorly integrated. Lastly, in 2024, following a national seminar organised in 2023 entitled “Qualitysafety approach in radiotherapy: what lessons have been learned after more than 15 years?”, ASN conducted a reflection on ways of developing its oversight. This reflection led it to hear all the stakeholders (professional organisations, health authorities) and other oversight authorities and to draw the lessons from a seminar on radiotherapy inspection practices organised by Heads of the European Radiological Protection Competent Authorities (HERCA). The new inspection guidelines of ASNR will be communicated to all the radiotherapy actors in early 2025. SUMMARY In radiotherapy, the inspections carried out by ASN over the period 2021-2024 and covering all the installed base, confirm that the safety fundamentals are in place: organisation of medical physics, equipment verifications, training in patient radiation protection and deployment of quality assurance procedures. ASN also underlines the progress in the area of clinical reviews with the setting up of experiments which will continue in 2025 before going into widespread application, and encourages the rapid extension of these reviews to radiosurgery. It also encourages the departments using new practices to assess them by putting in place procedures similar to the one developed on ASN’s initiative for adaptive radiotherapy. The analysis of the 2021-2024 period also confirms that the departments are struggling to maintain learning from experience procedures, with fewer meetings of experience feedback committees, insufficiently detailed ESR analyses and persistent difficulties in assessing the robustness of corrective actions. Although the continuing significant drop since 2015 in the number of ESRs notified to ASN can presumably be attributed in part to greater treatment safety, it also results from the departments’ difficulty in maintaining collective momentum. In addition, the prospective risk analyses are still insufficiently updated prior to organisational or technical changes or after analysing the lessons learned from events. The occurrence of events such as laterality and positioning errors, delineation of organs at risk and/or target organs still reveals organisational weaknesses and the need to regularly assess practices. Events resulting from failure to take earlier treatments into account remain an inspection priority for ASN, given their potential seriousness and the increase in the number of re-irradiations. ASN remains particularly attentive to the deployment of new techniques and practices in radiotherapy. After having encouraged the assessment of adaptive radiotherapy, ASN will continue its work in cooperation with the various institutional actors in the health sector, the professional organisations and assisted by its groups of experts, particularly Canpri, notably concerning flash radiotherapy. Lastly, in 2024, in a context of increasing complexity, fewer resources, extensive innovation and organisational changes, ASN defined the directions of its next four-yearly inspection programme in collaboration with the stakeholders and drawing the lessons from the inspection practices of its counterparts and other authorities in charge of activities involving risks. ASNR will communicate them to all the RNAs in early 2025. 2.2 Brachytherapy Brachytherapy can be used to treat certain pathologies and cancerous tumours in particular either specifically or as a complement to another treatment technique. This technique consists in placing radionuclide sources, in the form of sealed sources, either in contact with or inside the solid tumours to be treated. The main radionuclides used in brachytherapy are iridium-192 and iodine-125. Brachytherapy uses three techniques (detailed below), which differ more specifically in the dose rate applied according to the indications. As with radiotherapy, the radiation protection issues are linked to the intensity of the dose delivered to the patient and, if applicable, the high dose rates and the mastery of the equipment. Furthermore, as high-activity sources are involved, the management of emergency situations in the event of source jamming, as illustrated by the feedback from events notified to ASN, and the security of the sources, constitute specific risks of brachytherapy. That is why the ASN checks focus on the management of source security in addition to those on external-beam radiotherapy. 2.2.1 Description of the techniques The radiation protection risks in brachytherapy, apart from the problem of managing sealed sources, depend on the dose rate associated with the technique, the method of delivering the radiation to the tumour (permanent or temporary implantation, or temporary application). The use where necessary of source afterloaders means that the medical personnel do not have to handle the sources and allows the patient to be treated without irradiating the personnel. On the other hand, it is necessary to make provisions for accident situations associated with malfunctioning of the source afterloader and the high dose-rate delivered by the sources used. Low Dose‑Rate (LDR) brachytherapy is carried out at present using sealed sources of iodine-125 in the form of permanently implanted seeds, or caesium-137 applied temporarily. The dose rates are between 0.4 and 2 grays per hour (Gy/h). A new medical technique called “DaRT” (Diffusing alpha emitters Radiation Therapy) is currently being tested in a clinical investigation into the treatment of skin cancers. This technique consists in implanting sealed radium-224 sources which emit alpha particles in the tumour using an afterloader; the sources are left in the tumour for 15 to 20 days. ASN Report on the state of nuclear safety and radiation protection in France in 2024 223 Medical uses of ionising radiation 07 01 02 03 04 05 06 08 09 10 11 12 13 14 15 AP
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