ESTRO 37 Abstract book

ESTRO 37

S454

2 VU University Medical Center, Radiation Oncology, Amsterdam, The Netherlands 3 European Society of RadioTherapy and Oncology ESTRO, Bruxelles, Belgium 4 RadOnc eLearning Center- Inc, Fremont, USA 5 Institut Gustave Roussy, Radiation Oncology, Villejuif, France 6 Les Cliniques de l'Europe, Radiation Oncology, Bruxelles, Belgium 7 Centre Hospitalier Universitaire Vaudois, Radiation Oncology, Lausanne, Switzerland 8 University Hospital Zurich USZ, Radiation Oncology, Zurich, Switzerland Purpose or Objective To report the impact of 2 live FALCON contouring workshops (WS) on the inter-observer variation in gross tumor volume (GTV) and clinical target volume (CTV) contouring for spine stereotactic body radiotherapy (SBRT). Material and Methods We reviewed contouring data from participants at 4 spine SBRT contouring WS organized during the ESTRO35 (May 2016, Turin) and ESTRO36 (May 2017, Vienna) meetings. The clinical scenario was a patient with metastatic non- small cell lung cancer and good performance status, presenting with a painful vertebral metastasis. This abstract focuses on the GTV and the CTV defined consistent with RTOG/International Spine Radiosurgery consensus guidelines. Participants were asked to contour twice on 3 slices of a planning CT scan co-registered with MRI-images, once before and once after a teaching lecture. The data of participants who correctly submitted 2 contouring attempts - before and after the teaching - were analysed. Participants contours were benchmarked against a consensus contour agreed by the WS faculty and compared using the DICE index (DI). Data are reported as an average of the DI for all the participants. Results There were 141 participants (52% male, 48% female) from 31 countries. Most of those whose occupation was known were radiation/clinical oncologists (80/102). A total of 94/141 (67%) participants submitted at least one contouring attempt and 58/141 (42%) correctly submitted 2 contouring attempts. 141 CT slices were analysed. The average DI for GTV was 0.83 (+ 0.08, SD) before the teaching and 0.85 (+ 0.08) after (p=0.02). The average DI for the CTV was 0.73 (+ 0.18) before the teaching and 0.9 (+ 0.12) after (p<0.001). Conclusion Evaluation of the immediate impact of two-hours of contouring teaching is feasible and FALCON teaching methods can reduce inter-observer variability in target volume delineation. The long-term impact of the FALCON workshops remains to be evaluated. The ESTRO FALCON core is strongly committed to the further development of the current and future live and online FALCON workshops and to improving the adherence of the participants to the WS structure. PO-0867 Reporting of late morbidity after radiotherapy: review of the current practice in large studies. A.S. Vittrup 1 , K. Tanderup 1 , L.U. Fokdal 1 , J.C. Lindegaard 1 , R.A. Nout 2 , R. Pötter 3 , K. Kirchheiner 3 1 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark 2 Leiden University Medical Center, Department of Radiation Oncology, Leiden, The Netherlands 3 Medical University of Vienna/General Hospital of

allowed.

Results Median follow-up was 8 months (range: 2-15). Only 1/3 of tumors were irradiated: average BTV corresponded to only 33% of GTV (mean GTV volume 209 cc, mean diameter 7.8 cm). Average BTV´s SUVmax was 2.7 (cut off: 3) representing 15% of average GTV´s SUVmax. In all treated patients, a significant BE/AE was observed with mean bulky-shrinkage of 60% (range: 50-80%) after mean time of 2-3 weeks (Fig. 2). Overall response rates for symptom relief and mass response were 100%. Disease- specific survival was 96%. No patient experienced acute or late toxicity of any grade.

Conclusion The results confirm our hypothesis. Inducti of BE/AE using this new method could improve the thera peutic ratio. Large percentage of unresectable, partially irradiated bulky tumors was down-sized and converted to potentially resectable lesions (palliative treatment converted into potentially curative). This 1- day treatment seems to be more suitable for symptomatic patients with worse general conditions having also more convenient cost-effectiveness profile. Due to a very low radiation dose outside the bulky reaching OAR, it represents a very safe situation for the eventual re-irradiation in case of relapse. PO-0866 Interactive FALCON workshops reduce variability in contouring treatment volumes for spine SBRT B. De Bari 1 , M. Dahele 2 , M. Palmu 3 , S. Kaylor 4 , S. Rivera 5 , C. Salembier 6 , E. Rivin Del Campo 5 , L. Schiappacasse 7 , M. Guckenberger 8 1 Hôpital Univ. Jean Minjoz CHU Minjoz Jeans & Belfort- Montbéliard Hospital, Radiation Oncology, Besançon, France on

Vienna, Department of Radiation Oncology- Comprehensive Cancer Center, Vienna, Austria

Purpose or Objective