ESTRO 2021 Abstract Book

S534

ESTRO 2021

That several factors can contribute to the probability of local tumor control after fractionated radiotherapy was summarized originally by Withers (1975) as the “4 R’s” of radiotherapy: R ecovery from sublethal damage ( i.e. α/β ), cell-cycle R edistribution, cellular R epopulation ( i.e. D prolif ) and tumor R eoxygenation. Steel et al (1989) suggested intrinsic cellular R adiosensitivity as a fifth “R” to account for the different tolerance of tissues to fractionated irradiation. Both Biology and Physics inevitably change the balance of importance of these R’s as we move to hypofractionation, and Radiation Oncology is currently learning how best to take advantage of this new landscape in which the R’s are now living.

Teaching lecture: Clinical need vs technology push in innovation

SP-0664 Clinical need vs technology push in innovation D. Verellen 1 1 Iridium Network, Faculty of Medicine and Health Sciences, Antwerp University, Medical Physics, Antwerp, Belgium Abstract Text As George Orwell once wrote: “the true genius is to create a problem and then sell the solution.” The latter might offer a too sarcastic view on developments in radiation oncology as indeed our discipline is characterized by the synergy between increasing accuracy & precision in dose delivery and improving knowledge in radiobiology. As such improvements can only be encouraged. However, truth be said, one cannot ignore some bias created by enthusiasm, focusing on innovation and neglecting clinical priorities, which brings to mind Monty Python’s hospital sketch on the “machine that goes ping”. With this presentation the author suggests a short “time-out”, stimulating a critical review on some of the innovations that emerged the last decades in view of what is important to our patients and what is an optimal balance within the current challenges that we face in health care economics. Much like MLC’s were claimed a necessity for IMRT a few decades ago; MRI-linacs are being introduced as a prerequisite for real-time adaptive radiation therapy, arguments are being generated to boost the advantages of proton beam therapy, real-time tumour tracking presented as the ultimate motion management, FLASH as a game changer, and radiomics and AI as the future of automation and decision making. One might argue that some decisions supporting clinical introduction of novel technology are driven by a “me-too” argumentation rather than clinical relevance. Developments must be multi-disciplinary in nature, process-oriented rather than device-oriented, risk- and evidence- based, resource and risk optimised and flexible enough to cope with current and anticipated changes in oncology and health care. The multi-disciplinary radiation oncology community has an obligation to increase awareness and public confidence that radiation therapy is the most cost-effective cancer treatment (obviously, in optimal synergy with other cancer treatment modalities), and also that it is one of the safest medical specialties. New technology that is optimally implemented, appropriately applied and robustly assured will continue to support both of these messages. Abstract Text The upfront initial management of soft tissue sarcomas (STS) is very important, as it may impact on patients’ quality of life, especially in limb STS, and on outcome. Thus it is often multimodality especially in larger sarcomas. If surgery remains the pivotal treatment of STS, radiotherapy plays an important role and should be discussed within a multidisciplinary board meeting with results of biopsy, eventually re-examined by a dedicated sarcoma pathologist. STS are indeed rare tumours, very heterogeneous, with more than 100 pathological types and subtypes; molecular profiling has become of outmost importance as 40% of sarcomas are characterized by a molecular abnormality (translocation, amplification or mutation in tumour DNA) . An accurate diagnosis is important to decide upfront on the optimal management. Radiotherapy combined with surgery is part of the standard treatment in grade 2 and 3 STS of the extremities and superficial trunk >5 cm. Timing of radiotherapy can be pre-operative (50 Gy/25 fractions of 2 Gy) in case of larger STS or planned R1 resection. It can be administered post-operatively after “whoops surgery “ that is still too frequently observed; delivered dose is generally higher. Concomitant chemoradiotherapy (CRT) cannot be considered a standard treatment in limb and trunk STS. New approaches have been evaluated as neoadjuvant treatment such as nanoparticules, targeted agents, hyperthermia combined with radiotherapy, and immunotherapy with promising results in STS for some. Optimisation of radiotherapy delivery with intensity modulated radiotherapy and imaging guidance, adaptive strategies in pre-operative approaches, which may facilitate multi modality management, will be also addressed in our presentation. Randomized evidence (STRASS study) regarding retroperitoneal sarcomas will also be presented: pre-operative conformal radiotherapy with or without modulated intensity cannot be proposed systematically in daily practice; however role of radiotherapy may be discussed in some patients, based on subgroup analyses. Intensity modulated radiation therapy is more and more used. Finally we will address other approaches such as brachytherapy, proton therapy and carbon ion radiotherapy focusing on prospective evidence. Finally we will briefly address the role of stereotactic radiotherapy in a multi modality approach in the treatment of STS metastases. In conclusion, advances in radiotherapy may allow better integration with less toxicity and better outcome in multi-modality approaches in soft tissue sarcoma. However more prospective studies are warranted to validate them. Teaching lecture: Multi-modality treatment of soft tissue sarcoma SP-0665 Multi-modality treatment of soft tissue sarcoma C. Le Pechoux 1 , A. Levy 1 1 gustave Roussy Cancer Campus, Radiation Oncology, Villejuif, France

Teaching lecture: Distracting techniques for paediatric/AYA/adult radiotherapy