LES ACTIVITÉS NUCLÉAIRES : RAYONNEMENTS IONISANTS ET RISQUES POUR LA SANTÉ ET L’ENVIRONNEMENT Hadron therapy is a treatment technique based on the use of beams of charged particles (hadrons comprising protons and carbon ions), which can deliver the dose in a highly localised manner during treatments, thereby drastically reducing the volume of healthy tissue irradiated. In France, only proton therapy is used for clinical purposes. According to its advocates, hadron therapy with carbon ions is more suited to the treatment of the most radiation-resistant tumours and could result in several hundred additional cancer cases being cured each year. Adaptive radiotherapy is a radiotherapy technique that takes into account the movements and deformations of the organs and the tumour during the treatment. The treatment planning system recalculates the dose distribution before each delivery of the treatment fraction of the day, this new dose distribution is either accepted or not by the radiation oncologist. Two types of machines can deliver such adaptive treatments at present: ∙Ethos®, which uses 3D imaging obtained by the imager integrated in the accelerator (CBCT) to recalculate the dose distribution; ∙linear accelerators coupled to a Magnetic Resonance Imaging (MRI) machine, referred to as “MRI-Linac”, which uses MRI imaging to recalculate the dose distribution. Thanks to MRI, it is also possible to associate real-time monitoring (gating) of the target volume during delivery of the treatment. Since 2018, the combination of a linear accelerator for radiotherapy coupled with an MRI scanner has been developing. Given this context, ASNR wanted to encourage an initiative to assess this new technique. To this end, in late 2023 it initiated a study with the SFRO and the National Council of Radiation Oncologists (CNPO) to collect the data necessary for a large-scale assessment before the technique becomes widely adopted in France. A steering committee in which participate the HAS, the DGS, the General Directorate for Healthcare Organisation (DGOS), the National Cancer Institute (INCa), the SFRO and the CNPO, has been set up by ASNR to conduct and follow-up this study in compliance with the rules of good assessment practice. The evaluation methodology was validated at the end of 2024 for the MRI-Linac technique and the CBCT-Linac technique separately, by evaluating a tumour location of interest for each technique: unresectable pancreatic cancers for MRI-Linac and urothelial carcinomas of the bladder for CBCT‑Linac. Data collection is underway for bladder treatments. 6. IRSN report 2024-00179 of March 2024. Ultra-High Dose Rate Radiotherapy (UHDR) or FLASH radiotherapy is a technique that achieves a radiobiological effect, known as the “FLASH” effect, by using a beam of ionising radiation at a very high dose rate(6), with all types of beam (protons, electrons, photons, ions). The innovative nature of this effect lies in the improvement of the therapeutic index, enabling better protection of healthy tissues while maintaining tumour control, or even improving it under certain conditions. To achieve this, UHDR beams of at least 40 Gy/s in less than 100 ms appear to be necessary – whereas the dose rates used to date in conventional radiotherapy are of the order of 0.001 to 1 Gy/s. The development of this technique involves a paradigm shift, as the therapeutic approach focuses primarily on minimising side-effects rather than on tumour control alone. Achieving this effect would represent a break with current practice and pave the way for a potential reduction in side-effects for patients. This would enable better treatment of tumours that are currently difficult to treat with conventional radiotherapy (re-irradiation, radiation-resistant tumours, etc.). The development of this technique was the subject of a Canpri opinion in December 2025 and will be published in 2026. 2.1.2 – Technical rules applicable to external-beam radiotherapy facilities On account of the high dose rate and high energy of the beams when delivering the dose to the patient, the devices must be installed in rooms specially designed to guarantee radiation protection of the personnel, turning them into veritable bunkers in which the wall thickness can vary from 1 to 2.5 metres of ordinary concrete. A radiotherapy installation comprises a treatment room including a technical area containing the treatment device, a control station outside the room and, for some accelerators, auxiliary technical premises. The bunker with shielding baffle remains the reference insofar as it reduces the shielding required at the ventilation duct and electrical duct inlets and provides greater security in the event of failure of the door motorisation system or if anyone gets accidentally locked inside. However, if the space available to the licensee is limited, which compromises the installation of the accelerator, a smaller shielding baffle, or even none at all, can be envisaged under certain restrictive conditions. Moreover, the arrival of self-shielded MDs such as the ZAP-X® platform makes it possible to consider installations 0 20 40 60 80 100 120 Bordeaux Caen Châlons-enChampagne Dijon Lille Lyon Marseille Nantes Orléans Paris Strasbourg Licensed centres (legal entities) Accelerators New licences/license renewals 26 28 21 84 15 8 5 7 4 24 20 23 17 14 7 9 27 33 16 25 3 7 6 58 69 82 65 11 19 11 8 3 109 GRAPH 1 Breakdown of the number of centres and external-beam radiotherapy accelerators, by ASNR regional division, and the number of new licences or licence renewals by ASNR in 2025 ASNR Report on the state of nuclear safety and radiation protection in France in 2025 199 01 05 02 03 04 09 06 10 07 11 13 08 12 A / Z
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