ESTRO 37 Abstract book

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ESTRO 37

but also for other indications of thoracic radiotherapy (e.g. breast, lymphoma and oesophageal cancers). EP-1406 Feasibility study of contouring heart structures and development of atlas for lung cancer planning N. Mohammed 1 , K. McLellan 2 , B. McCann 1 , Y. Flannigan 3 , R. Woodward 4 , P. Kelso 3 , M. Glegg 3 , K. Mangion 5 , P. McLoone 6 , S. Smith 3 , M. Sankaralingham 1 1 Beatson West of Scotland Cancer Centre, Radiation Oncology, Glasgow, United Kingdom 2 Edinburgh Cancer Centre, Radiation Oncology, Edinburgh, United Kingdom 3 Beatson West of Scotland Cancer Centre, Radiation Phyiscs, Glasgow, United Kingdom 4 Glasgow Research Imaging Facility, Cardiovascular, Glasgow, United Kingdom 5 British Heart Foundation Cardiovascular Research Facility, Glasgow University, Glasgow, United Kingdom 6 Glasgow University, Statistics, Glasgow, United Kingdom Purpose or Objective Lung cancer has the highest mortality rate and new data suggests, noncancer deaths affect survival outcomes in patients treated with radiotherapy. Subsequent studies have investigated radiation dose to the whole heart and found contradictory results. The heart is a complex organ with multiple sub-structures, therefore it is likely that simply one DVH parameter will not be sufficient to identify acute cardiac toxicity. We developed a detailed contouring atlas to contour heart sub-structures, in order to investigate the relationship of radiation dose to those substructures in patients treated with thoracic radiotherapy. Material and Methods

structures were contoured on 5 lung cancer patients by 3 oncologists. Contouring variability was assessed using Eclipse Treatment Planning System v15.5 [Varian Medical Systems, Palo Alto, CA, USA] to compute concordance metrics. The contours by Clinician involved in development of contouring atlas with input from cardiologist and cardiac radiographer was used as standard contour for comparison. DICE coefficents were calculated to compare the delineated structures of each operator with those of these standard contours.

Results

Structures outlined were sinoatrial node (SA), atrioventricular node(AV), SVC, pulmonary artery (PA), aortic valve(A valve), mitral valve(M valve ), pulmonary valve(Pulm valve), triscuspid valve (T valve), left and right chambers – LV, RV, LA, RA. The left ventricular muscle was contoured into 17 segments, which were then combined to form the left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA) circulation territories. The developed contouring atlas was used to contour five patients (Figure 1 – page 2 of atlas). The heart contour volumes for the five patients ranged from 524-1118 cm 3 , AV node 2.6-8.5 cm 3 , SA node 0.79- 4.94 cm 3 , A valve 6.1-12.8 cm 3 , Pulm valve 3.9-11.5 cm 3 , M valve 1.8-6.1 cm 3 , LAD 7.1-180.7 cm 3 , RCA 9.3-15.6 cm 3 , and LCX 13.2-18.7 cm 3. The great vessels (SVC and PA) were contoured within the vicinity of the heart volume, and the intention would be to use the maximum dose DVH parameter. The contour overlap was better for the heart chambers (Figure 2 mean Dice coefficient for contours), the mean DICE coefficient for left ventricle was 0.9 (SD 0.05) and ranged from 0.78-0.9 for the 4 heart chambers. The heart substructures demonstrated less overlap mean DICE coefficient ranged from 0.35-0.6 and the coronary artery territories showed less overlap whereby mean DICE coefficient ranged from 0.26-0.36. Conclusion The atlas facilitated heart substructure contouring and the variation in structures is acceptable given the smaller volumes. The atlas will be validated in a cohort of lung cancer patients. EP-1407 Dosimetric Variables for Chest Wall Pain following Lung Stereotactic Body Radiotherapy C. Pembroke 1 , J. Albers 2 , J. Kildea 3 , W. Parker 4 , S. Faria 3 1 Velindre Cancer Centre, Clinical Oncology, cardiff, United Kingdom 2 McGill University, Radiation Oncology, Montreal, Canada 3 McGill University Health Centre, Radiation Oncology, Montreal, Canada 4 McGill University Health Centre, McGill University, Montreal, Canada

The atlas was developed by a team involved in a cardiac toxicity study (CART study). The atlas was used to assess reproducibility of contouring heart substructures. Fifteen