Contouring variations and the role of atlas in non-small cell lung cancer radiation therapy: Analysis of a multi-institutional preclinical trial planning study

Abstract

Purpose To quantify variations in target and normal structure contouring and evaluate dosimetric impact of these variations in non-small-cell lung cancer (NSCLC) cases. To study whether providing an atlas can reduce potential variation. Methods and Materials Three NSCLC cases were distributed sequentially to multiple institutions for contouring and radiotherapy planning. No segmentation atlas was provided for the first two cases (Case1 and Case2). Contours were collected from submitted plans and consensus contour sets were generated. The volume variation among institution contours and the deviation of them from consensus contours were analyzed. The dose-volume histograms (DVH) for individual institution plans were re-calculated using consensus contours to quantify the dosimetric changes. An atlas containing targets and critical structures was constructed and was made available when the third case (Case3) was distributed for planning. The contouring variability in the submitted plans of Case3 was compared with that in first two cases. Results Planning Target Volume (PTV) showed large variation among institutions. The PTV coverage in institutions’ plans decreased dramatically when re-evaluated using the consensus PTV contour. The PTV contouring consistency did not show improvement with atlas use in Case3. For normal structures, lung contours presented very good agreement, while the brachial plexus showed the largest variation. The consistency of esophagus and heart contouring improved significantly (t-test, p<0.05) in Case3. Major factors contributing to the contouring variation were identified through a survey questionnaire. Conclusions The amount of contouring variations in NSCLC cases was presented. Its impact on dosimetric parameters can be significant. The segmentation atlas improved the contour agreement for esophagus and heart, but not for the PTV in this study. Quality assurance of contouring is essential for a successful multi-institutional clinical trial.

The impact of training and professional collaboration on the interobserver variation of lung cancer delineations: a multi-institutional study

“…For future studies, delineation atlases could also be provided to participants so as to reduce interpretational differences of what should be included in the GTV. The delineation data gathered from these courses could then be used to improve these atlases with the aim to further reduce the interobserver variation in the delineation of the GTV [27,28].…”

MRI-guided lung SBRT: Present and future developments

“…Delineation uncertainties are larger for OAR as CT features relatively poor soft-tissue contrast (see Fig. 4), resulting in uncertainties of up to a few centimetres for the oesophagus and spinal cord [84]. The improved soft-tissue contrast of MRI may lead to a reduction in contouring variability for these structures.…”

NCTN clinical trial standardization for radiotherapy through IROC and CIRO

“…Standardization of targets and critical structures delineation are of utmost importance in the radiotherapy process. Variations in structure delineation are found to be the most significant among all the radiotherapy processes . To facilitate contour review with automation, IROC has built atlases for multiple disease sites from the submitted cases.…”