ESTRO 2023 - Abstract Book

S836

Tuesday 16 May 2023

ESTRO 2023

defined as those with no associated actual or threatened pathological fracture and no neurological complications and the second on complicated bone metastases. The uncomplicated section covers diagnosis, the concept of oligometastases and their management, dose, fractionation and technique for external beam radiotherapy and includes reirradiation. Clinical assessment should include a pain score, performance status and an estimation of the predicted survival. Single doses are advocated for both initial and reirradiation of painful bone metastases; the concept of pain flare after radiotherapy is recognised and high dose stereotactic radiotherapy and IMRT are not recommended in the absence of clear evidence of their superiority over simpler techniques. The complicated bone metastases section covers pathological fracture, spinal canal compression, neuropathic pain and prophylactic treatment. In metastatic spinal canal compression full evaluation with whole spine MRI and surgical referral for spinal instability is recommended. Surgical referral should also be considered for single site compression in patients with < 48 hours paraplegia and life expectancy of >3 months. High dose steroids and local radiotherapy using single doses of 8-10Gy are otherwise recommended. Re-irradiation is possible within a cumulative dose limit of BED ≤ 100 - 135.5 Gy2. Stereotactic radiotherapy is not recommended for cord compression. Neuropathic pain should be treated with a single dose of 8Gy. Pathological fracture risk should be undertaken using established scoring systems. Single doses of 8Gy, 20Gy in 5 fractions or 30Gy in 10 fractions should be used for threatened or actual pathological fracture where surgery is not feasible. All recommendations are evidence based with levels of evidence referenced throughout. SP-0995 An ESTRO-ACROP guideline on quality assurance and medical physics commissioning of online MRI-guided radiotherapy systems based on a consensus expert opinion S. Tanadini-Lang Switzerland SP-0996 Overview of the ESTRO-ACROP guideline for positioning, immobilisation and set-up verification for loco regional photon breast cancer irradiation M. Mast 1 1 Haaglanden Medical Center, Radiotherapy, Leidschendam, The Netherlands Abstract Text Various studies can be found in the literature on improvement of positioning and position verification in breast cancer. However, there is no practical overview of how best to meet these accuracy requirements. Therefore, a guideline has been developed regarding the strategies for positioning, immobilisation, setup and position verification used for loco-regional photon irradiation of breast cancer. The purpose of the guideline is to provide practical recommendations to improve the accuracy of breast cancer irradiation. Opportunities for future research priorities are also described. A literature search was conducted identify relevant studies and to provide recommendations where appropriately supported by evidence. In addition, the authors included considerations in areas of practice of which there is a limited level of evidence. The literature overview was supplemented with the experience and specialist knowledge of the globally distributed guideline authors. The literature review showed that in 90% of the studies, patients are most frequently positioned supine. Based on the literature and the current equipment the advice is that for most breast cancer treatments, the supine position is the standard position. Large breasted patients or patients requiring a higher degree of lung sparing may benefit from the prone position if the equipment and expertise are available. Both arms up is considered more stable; though one arm up may be considered for patients who cannot tolerate both arms up. In the supine position, both flat and elevated positions are acceptable, provided collision risks are managed and the patient is properly stabilized to prevent position variation from the patient shifting down the incline of elevated boards. In patients with a superior breast fall, the elevated position could be used. In addition to stability and comfort, the patient's experience should also be considered from the perspective of dignity when assessing the patient's position. Apparently, there is a lack of evidence in this area, therefore departments are encouraged to involve patients in evaluating new patient positioning workflows. Furthermore, while lacking formal evidence, the authors strongly recommend the use of positioning aids that can be indexed to both the treatment table and skin reference marks for efficient and accurate patient positioning. In addition to general patient positioning considerations, more specialized immobilization devices can be used with the aim of stabilizing the breast in a position more favourable for treatment planning. There is insufficient evidence from the literature to support the use of a specific breast immobilization device. The pros and cons of specific immobilization devices should be carefully weighed and evaluated by the local department prior to clinical implementation. The use of skin marks to aid patient setup are advised, however a growing body of evidence involving surface-guided imaging (SGRT) suggests the use of such technology may be a reliable alternative. The use of permanent skin marks should be considered taking into account long-term patient experience and patient preference. When SGRT is not available, the authors recommend the following configuration of skin marks: · Caudal: one skin mark on the sagittal midline of the patient; · Lateral: two marks on either side of the patient in the middle of the chest, as these are stable points. Daily 2D-2D or 3D online position verification should be used whenever possible. However, 2D online/offline position verification is appropriate with consideration of limitations in detection and correction of setup errors. Image matching should take into account bone anatomy and soft tissue displacement/deformation. While several studies have evaluated SGRT as a replacement for more conventional IGRT, it is advised that departments validate this within their own local workflows to ensure treatment accuracy is maintained. Abstract not available

SP-0997 Consensus statements on integration of radiation therapy with targeted treatments for breast cancer I. Meattini 1