ESTRO 2024 - Abstract Book

S149 ESTRO 2024 point for significant (and accelerating) physics and technological innovations, that have provided strong drivers for radiotherapy improvement over the last 40 years. These were underpinned by the widespread availability of relatively stable linacs through the 1970s and the growing availability of CT-simulators into the 1980s. Anders Brahme’s seminal paper laying the foundations of IMRT had been recently published (1982). Since then, there have been a multitude of developments (and acronyms!), including MLCs, EPIDs, volumetric OBI, IMRT, VMAT, SBRT, kV-IGRT, ART, MRIgRT, BiGRT (and BiGART), the growing use of particle therapy (particularly PBT, but also HI-PT), and many more. In addition, there have been numerous linked, associated and parallel developments improving accuracy, precision, quality, process, etc. A 2016 Dutch study indicated that centres introduced 12 innovations per year on average (and up to 25), whilst other studies have shown the variable rollout of innovations, dependent on a range of factors and/or barriers. Nevertheless, the innovation evolution continues unabated; radiotherapy is currently stepping over the threshold of rapidly increasing automation and AI applications. Many such innovations have been adopted based on modelled improvements, but without strong clinical evidence of their impact on patient outcomes. This may be appropriate where improved process or information is achieved, or where implementation clearly leads to well defined clinical trials. However standard clinical trial approaches often may not be best-suited to evaluate new technologies in radiotherapy, presenting both equipoise and logistical challenges. The latter includes that the technology must be installed and in place before trials can be conducted, committing the necessary resources up front, making high-cost innovations problematic and cost-benefit a necessary part of the evaluation. Therefore, other methods are required to be used to help bridge this evidence gap, both for pre-installation decisions to enable assessment and evaluation of novel technologies for the clinical setting, and then post-installation for evidence-based clinical decisions on optimum patient selection and treatment. These include specific study types, e.g. more systematic modelled approaches in in silico trials, and also frameworks combining different types of evidence from different data sources (e.g. ANROTAT, R-IDEAL). Some examples of such approaches can be illustrated, using previous technology introductions. These include the still-current expanding implementation of MR-linacs and particle therapy, initially developed and implemented based on alternative methods; but once a suitable technology base was in place, maturing in evaluation by increasing use of robust conventional clinical trials. Looking ahead, other observational possibilities are emerging or strengthening, e.g. the potential role of using real-world data in various ways, such as prospective registries, causal inference and iterative data-driven improvement in learning health systems. Physics and technology innovations will continue to evolve and multiply. Even when we can’t randomise, and the high-level evidence is poor or non-existent, we must generate, develop and apply the best evidence we can, within structured consistent methodologies, to support clinical decisions and to complement and lead in to randomised clinical trials when possible. Invited Speaker

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The radiobiological principles of low dose radiotherapy for non-cancer diseases

Nicolas FORAY 1 , Eymeric Le Reun 2

1 INSERM U1296 Unit, Centre Léon-Bérard, Lyon, France. 2 INSERM U1296, Centre Léon-Bérard, Lyon, France

Abstract:

Early after the discovery of X-rays, ionizing radiation (IR) were used in numerous applications different form treatments against cancer. Such applications generally involved doses lower than 1 Gy per session. Progressively in oncology, the dose per session increased. However, the approach consisting in delivering less than 1 Gy per session, called low dose radiation therapy (LDRT), was preserved and is still applied in different forms and in very specific cases: let's cite the historical cases of some trials to treat benign meningiomas, tinea capitis, pain related to rhumatological diseases and more recently to protect against lung inflammation after COVID-19 infection or to treat