ESTRO 2021 Abstract Book

S106

ESTRO 2021

A. Gawish 1 , A. Mpotsaris 2 , I. Sandalcioglu 3 , K.P. Stein 3 , T. Brunner 4 1 Medical Faculty University Hospital Magdeburg, University Clinic for Radiation Therapy, Magdeburg, Germany; 2 Medical Faculty University Hospital Magdeburg, University Clinic of Neuroradiology, Magdeburg, Germany; 3 Medical Faculty University Hospital Magdeburg, University Clinic of Neurosurgery, Magdeburg, Germany; 4 Medical Faculty University Hospital Magdeburg, University Clinic of Radiation Therapy, Magdeburg, Germany Purpose or Objective Purpose : The LINAC stereotactic radiosurgery (SRS) procedure is gaining popularity as a form of radiation treatment for cerebral arteriovenous malformations (AVMs) since the theory of combined SRS and endovascular treatment poses much uncertainty. This study focuses on how to evaluate obliteration and re- bleeding rates, and to determine factors and adverse effects influencing obliteration after LINAC-based SRS for cerebral AVMs. Materials and Methods Methods and materials : ExacTrak software-guided LINAC SRS was conducted in 64 patients with cerebral AVMs. About 65 percent of the AVMs were > 2 cm in diameter and the median and mean treatment volumes were 5.6 cc and 14.8 cc, respectively (range 0.258-180.06 cc). AVM treatment doses ranged from 16.4 to 24 Gy (median: 19 Gy) in 1-4 fractions. Using Kaplan-Meier survival and life table analyses, actuarial obliteration and annual bleeding hazard rates were calculated after SRS. Results Results : After a mean follow-up of 38 months (range 6-120 months) the AVM was completely obliterated in 36 /64 patients, partially obliterated in 4/64, while the treatment resulted in no response in 13/64 patients. 11 patients have inadequate follow-up. The median time for the obliteration was 25 months. The actual obliteration rates after 2 and 3 years were 40 and 75%, respectively. Prior endovascular embolization had a significant positive effect on the obliteration rate (p = 0,015). 12,5 % of AVM patients showed no angiographically confirmed obliteration after 3 years, all received annual follow-up DSA or MRI and both showed no bleeding. Only two patients had bleeding after SRS at a mean of 48 months. The annual bleeding hazard rate in the first two years was 1.5 % . Asymptomatic abnormalities were detected after imaging in 70 % of patients. 14 % of the patients (n=9) suffered from radio-necrosis.

Conclusion Conclusion : It may be concluded that SRS is an important form of treatment for AVMs. Patients need careful follow-up due to the overall high rate of radiation-induced imaging and a possible risk of late treatment side effects. For a proper assessment of the treatment effect a minimal follow-up of 3 years is mandatory.

Award lecture: E van der Schueren Award

SP-0173 ESTRO Education: What did we learn from COVID-19? J.G. Eriksen 1 1 Aarhus University Hospital, Experimental Clinical Oncology, Aarhus, Denmark

Abstract Text Since the first ESTRO course in 1985 , ESTRO education and ESTRO School has experienced a constant growth in terms of educational activities and attendees. ESTRO School has surely provided the most comprehensive post- graduate educational radiation oncology program in the world. The program for 2020 was no exception. It was planned to be one of the biggest programs with 40 live courses, 10 online contouring workshops and four new courses in the pipeline. In March, COVID-19 did set everything on hold and 37 courses were cancelled or postponed. Al new developments were put on hold. A plan was set up to deal with this situation and seven online courses were launched in 2020 with excellent support from all stakeholders and faculties. Several different models were developed and, in the end, online courses turned out to be a success that could be handled in ESTRO School. The lecture will describe the development of the online activities and discus the potential and challenges at present as well as the future role and andragogical implications for online course activities in the ESTRO School.