ESTRO 2023 - Abstract Book

S140

Saturday 13 May

ESTRO 2023

prognosis etc.). Beside these relatively obvious and straightforward objectives, the evaluation of novel AI has to satisfy the recently updated E.U regulation. Another key aspect of the evaluation of AI tools is to enlighten the equipment choice for end-users, often lost in the massive diversity of emerging tools, culminating in solicitation for constant updates/upgrades. The move for AI-based technologies not only comes at a financial cost but also with a change in practice; the investment should come with a tangible benefit. We will present our experience with AI-based technology implementation in our institution, focused on three examples: auto-contouring, pseudo-CT and immunological optimization of radiotherapy. We will address the critical steps for a straightforward validation assessment, the strategy chosen for the selection of metrics and their anticipated impact on clinical practice. We will also comment on the needs for a robust medico-economics assessment – that may also include the carbon performances and environmental concerns, if any – to provide the payers the arguments for any additional investment. SP-0194 MR-guided radiotherapy - What are the remaining elephants in the room and how should they be tackled? A. Sahgal 1 1 Sunnybrook Odette Cancer Center, Radiation Oncology, Toronto, Canada Abstract Text The aim of this presentation if to provide the audience with the approach developed at the Sunnybrook Health Sciences Center specific to MR-Linac adaptive radiotherapy for brain tumours. Our program initially treated with an adapt-to-position strategy and developed advanced research imaging capacity on the MR-Linac itself. As our workflow and understanding of the technology matured, we began the first trial of adaptive margin reduced radiotherapy for high grade glioma. The UNITED (UNIty-Based MR-Linac Guided AdapTive RadiothErapy for High GraDe Glioma: A phase 2 Trial, NCT04726397) trial is the first of its kind with a 5 mm personalized clinical target volume, that can be adjusted to take involved FLAIR, with weekly on-line adaption during either a patient’s 3 or 6 week course of radiotherapy concurrent with temozolomide. The UNITED trial is nearly complete with a target accrual of ~100 patients. The next phase of glioma adaptive trials has already begun at the Sunnybrook Health Sciences Center. We have learned much as to the technical challenges and opportunities. Our aim ultimately is to apply MRI-based quantitative metrics to identify areas to dose escalate or de-escalate during a patient’s treatment course. We are excited to share with you this unique experience to advance and modernize radiotherapy for this challenging disease.

Symposium: Controversies in postoperative radiotherapy of oral cavity cancer

SP-0195 Margins and elective nodal irradiation in PORT - How much do they matter? V. Gregoire France

Abstract not available

SP-0196 What role for brachytherapy and SBRT? A. Budrukkar 1 1 Tata Memorial Hospital, Department of Radiation Oncology, Mumbai, India

Abstract Text Role of radiotherapy as an adjuvant treatment of oral cavity cancers is well established. Standard indications for adjuvant radiation include T3-T4 tumor, node positive disease, margin positivity and extranodal extension. Concurrent chemotherapy is considered in presence of margin positivity and extra-nodal extension. External beam radiation therapy (EBRT) to a dose of 56-64Gy in conventional fractionation is the standard of care as an adjuvant therapy. There are certain indications such as margin positivity and extra-nodal extension where dose escalation has shown to be beneficial in terms of locoregional control. Apart from EBRT, possible options for dose escalation are brachytherapy (BT) and stereotactic body radiation therapy (SBRT). Both BT and SBRT can possibly be considered either alone or in combination with EBRT. In situations where neck irradiation is not warranted these 2 modalities may be considered as a radical treatment. In patients with margin positive status these 2 modalities are useful as local dose escalation strategies without increase in the toxicity. BT although an invasive modality can improve local control by local dose escalation. Due to the rapid fall off of the dose there is reduction in late toxicity such as xerostomia. BT can be considered either after surgical wound healing or can be considered as a peri-operative approach. While peri-operative BT is more advantageous for the patient due to convenience and no need for repeat anaesthesia, it may not be feasible in some centres and requires close collaboration with surgical team. BT can also be considered as a boost after EBRT where addressing the neck nodes is necessary. SBRT on the other hand is a non invasive technique which may be considered for similar indications of BT. The dose fall off in SBRT however may not be as rapid as in BT. SBRT can also be considered either alone or in combination with EBRT. One of the potential utility of SBRT could be in local dose escalation for the nodes which have extra-nodal extension. However more work is needed to establish its efficacy for this indication. While use of both BT and SBRT still remains controversial in the management of adjuvant treatment of oral cavity cancers, both may have a role in certain scenarios which needs to be evaluated in prospective studies.

SP-0197 Revisiting concurrent postoperative chemoradiotherapy - What do we know? J.G. Eriksen 1 1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark

Abstract Text