7th ICHNO Abstract book

page 58 7 th ICHNO Conference International Conference on innovative approaches in Head and Neck Oncology 14 – 16 March 2019 Barcelona, Spain __________________________________________________________________________________________ 7th ICHNO

contoured. Volumes and DICE similarity coefficients (DSC) of the submitted structures were measured and calculated. Results A total of fourteen centres (60.9%) completed both survey and delineations. Regarding CTVp, nine centres (64%) used delineation guidelines, although they all referred to different ones. All centres used isotropic margins from GTVp to CTVp between 5 and 12 mm. Three centres used two types of margins; namely a boost (5-10mm) and a prophylactic margin (10-15mm). All centres corrected for anatomical boundaries such as air and bone. The mean volume delineated for cases 1 through 5 were 92.1cc (range 67.0-118.3cc), 77.9cc (range 45.9-109.2cc), 90.6cc (range 53.8-145.3cc), 40.7cc (range 7.2-91.6cc) and 64.4cc (range 30.3-91.6cc) respectively. Average CTVp DSC for all five cases was 0.7 (range 0.51-0.78) (Figure 1). Regarding CTVe, all fourteen centres used delineation guidelines and twelve explicitly referred to the guidelines published by Grégoire et al. Good agreement was shown for neck level II, III and IV, while worst consensus was observed for level Ib, V, VI and VII. This resulted in mean volumes for cases 1 through 5 of 147.5cc (range 113.7- 215.2cc), 209.1cc (range 183.5-258.2cc), 179.1cc (range 134.9-268.9cc), 121.6cc (range 78.4-199.1cc) and 271.1cc (range 215.7-421.3cc) respectively. Average DSC for CTVe was 0.7 (range 0.67-0.74) for all patients (Figure 2).

Material and Methods Patients with intermediate and high risk, locally advanced OPSCC receiving radical RT/CRT were recruited to this prospective observational imaging study with national REC approval (15/WS/0159); A feasibility study was carried out to evaluate the viability of this approach in the 1 st 20 patients recruited. Patients underwent DW- MRI immediately prior to #1and #11. 3D target lesions were defined on each MRI by a clinical oncologist and radiologist. ADC measurements were obtained for each target lesion (primary and lymph nodes), and % change in ADC calculated. Disease status for each target lesion is noted at follow up at 6, 12, 18 and 24 71 patientshave been recruited to date. The first 20 patients were recruited over a 10 month period, with a high recruitment up-take of approximately 62.5% of those screened. Of the first 20 patients recruited 16 patients (80%) completed both MRI scans. One patient underwent MRI-1 and declined MRI-2 as they felt unable to tolerate the scan. Three of the patients were unable to undergo the 1 st MRI therefore were withdrawn before being scanned (1- poor IV access for contrast, 1- unable to tolerate the scan, 1 - MRI unavailable). All 16 scanned patients had at least one target lesion that was measureable on DW MRI baseline and repeat image for the purposes of recording ADC Conclusion Feasibility work has demonstrated good patient compliance with scanning requirements and the ability to measure ADC in target lesions suggesting this is a viable approach to identifying the sub-group of non-responders during RT which may ultimately allow individualised and adaptive treatment intensification. Establishing ADC thresholds that predict for local failure is an essential step towards using DW-MRI to improve the therapeutic ratio. The MeRInO study will help establish these thresholds in OPSCC. PO-114 Variability in target volume delineation in Head and Neck cancer: Results of a national study J. Van der Veen 1 , A. Gulyban 2 , S. Nuyts 1 1 University Hospitals Leuven, Radiotherapy-Oncology, Leuven, Belgium ; 2 Europe Hospitals Brussels, Department of Radiation Oncology, Uccle, Belgium Purpose or Objective Over the past twenty years, technological innovations in the radiology and radiotherapy field have allowed more accurate visualisation and treatment of cancers. The result has been improved disease outcome and a decrease in toxicity. Precision of radiotherapy treatment is still continuously improving, demanding more accurate delineations to fully exploit these developments because errors in the delineation process can have an impact on the entire treatment process. The aim of this study was to identify to which extent guidelines are used, which guidelines are used and the degree of interobserver variability in delineation of head and neck cancer. Material and Methods Five head and neck cancer cases were send to all Belgian radiotherapy departments in 2017 and centres were asked to submit clinical target volumes (CTV) of the elective neck (CTVe) and the primary tumour (CTVp) in addition to an online survey. Gross tumour volume of the primary tumour (GTVp) and involved nodes were already months. Results

Conclusion