ESTRO 38 Abstract book

S289 ESTRO 38

cervical cancer the last decade [Sturdza et al 2016]. Several studies have addressed the added value of fraction specific imaging and re-planning, e.g. for breast [Altman et al 2018], bladder [Bus et al 2018], cervix [Nesvacil et al 2013 and Skliarenko et al 2018] and prostate [Simnor et al 2009]. Skliarenko et al suggested for example that the first implant, used for delivering two fractions, could be performed only with intracavitary applicators and that the addition of needles in the second implant could be performed if the dosimetry of the first implant was suboptimal. Another important principle of adaptive radiotherapy is to record the actual dose distribution that is delivered to the patient. In EBRT the CBCT is performed in room with the patient on the treatment coach. Except for US-guided brachytherapy, such in room imaging systems is usually not used in brachytherapy centers, even though some centers has developed in room MR and CT facilities. This means that the patient is moved from the brachytherapy suite to the imaging device and then to the treatment room with inherent risk of altering the position of the applicator. Therefore, the need of treatment monitoring and verification has emerged. Some very interesting technology has been developed and implemented recently. One of them is electromagnetic (EM) tracking where the position and orientation of one or several small coils (sensors) are detected within a known electromagnetic field. Additional, new developments in real-time in vivo dosimetry are also promising and it has been demonstrated that it can be used for source tracking during treatment delivery. However, the limitation of source tracking is of course that it tracks the source in relation to the detector, and not in relation to the anatomy. The ultimate goal would be to combine the source tracking with imaging, which some groups are working on. Moreover, at the end of the day the ability to perform true adaptive BT treatment requires fast recalculation algorithms/procedure, which is rather similar to challenges seen in EBRT. SP-0549 How to organise your department to have a structured way of collecting toxicity data J. Widder 1 1 Medical University Vienna, Radiation Oncology, Vienna, Austria Abstract text Reducing toxicity is a central paradigm for all local treatment modalities in oncology. Minimally invasive and robot assisted surgery, local ablation options, increasing conformality and beam modulation in radiotherapy as well as the implementation of protons all intend to reduce toxicity. RT has highly quantitative, modellable, and actionable causal data of toxicity, more than any other discipline: this renders RT a paradigm discipline of precision medicine striving towards improving the fit between oncological condition of a patient and tailored treatment. Why then are actionable RT toxicity data still relatively scarce? How to assess toxicities is navigating between specificity (is this toxicity radiation- induced?) and relevance-for-patients (does this toxicity actually bother patients?). Quality-of-life, functioning, symptoms, toxicity scores: which outcomes matter most, and which are actually used in treatment decisions. Clinical relevance is crucial, and any threshold- level of clinical relevance will require consensus. In order to be effective, collecting toxicity data at a department need to be part of a larger endeavour of collecting patient-data, data about the disease and comorbidity, surgery and systemic treatments and detailed Symposium: Predictive models of toxicity and big data, big open issues

It is important to consider the role of QA together with audit programmes both during the implementation phase and also on a routine basis following the implementation of the new evidence based standards. This should include process mapping and resource assessments for each step in the ART process. RTTs are a key component of this process within the MPT. The advent of real-time ART techniques, particularly utilising the MR-linac technology, presents an opportunity to improve outcomes for a number of disease sites and for RTTs to further extend their role within the patient pathway. However, this also presents challenges from a training perspective for RTTs to ensure correct interpretation of on-line image guidance, now with both CBCT and MR modalities. Conclusion Utilisation of national recommendations or clinical trial processes ensure that ART can be developed and implemented safely and accurately within a multi- professional team environment. Advanced ART techniques provide an opportunity for RTTs to extend their roles and scope of practice. This can be achieved by developing an educational framework which includes ART. References 1 National Radiotherapy Implementation Group Report. Image Guided Radiotherapy. Guidelines for Implementation and use. SP-0548 Adaptive and Real-time Approaches in Brachytherapy T.P. Hellebust 1 1 Oslo University Hospital/University of Oslo, Department of Medical Physics/Physics Department, Oslo, Norway Abstract text For the last 25 years radiotherapy treatment planning has evolved from a 2-dimentional (2D)-approach using radiographic films to an approach where the planning is based on 3D imaging showing the target volumes and the normal tissue. This enables conformation of the dose distribution to the target volume(s) and avoidance of high dose to organs at risk (OARs). Broad implementation of 3D planning in external beam radiotherapy (EBRT) already took place around the end of the 90ties and was considered as state of the art rather soon. In brachytherapy (BT), however, the transition from 2D to 3D based planning started much later and is not until recently considered as the state of the art, especially for GYN, prostate and breast BT. The 3D imaging approach for treatment planning is rather different for EBRT and BT. In EBRT the treatment is traditionally based on pre- treatment imaging acquired typically a few days or up to a week before treatment start. Due to development of on board anatomical imaging, using cone beam CT and lately MR imaging, many groups have for the last years worked on procedures for treatment plan adaptation during the EBRT treatment schedule. In BT, on the other hand, many centres developed procedures with a dedicated imaging procedure for each fraction already from the beginning of the 3D area. Such procedure facilitates the opportunity to prepare a new fraction specific treatment plan taking into account the dose distribution in previous fractions, in fact the core principle of adaptive radiotherapy. Additionally, the limited requirement of tissue density to have accurate dose calculation, means that MR and/or ultrasound (US) based treatment planning has played an important role since 3D planning was introduced in brachytherapy more than a decade ago. Image guidance in BT is used for navigation of the implant and individual dose adaptation. In fact, when image guided brachytherapy is given as boost at the last part an EBRT schedule, an adaptive target volume is identified. This means that the dose is delivered to the residual limited sized target volume and not to the initial target volume which may be significantly larger. Such approach has successfully been applied in definitive treatment of