Abstract
PurposeTo 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 materialsThree NSCLC cases were distributed sequentially to multiple institutions for contouring and radiation therapy planning. No segmentation atlas was provided for the first 2 cases (Case 1 and Case 2). 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 for individual institution plans were recalculated 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 (Case 3) was distributed for planning. The contouring variability in the submitted plans of Case 3 was compared with that in first 2 cases. ResultsPlanning target volume (PTV) showed large variation among institutions. The PTV coverage in institutions’ plans decreased dramatically when reevaluated using the consensus PTV contour. The PTV contouring consistency did not show improvement with atlas use in Case 3. 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 < .05) in Case 3. Major factors contributing to the contouring variation were identified through a survey questionnaire. ConclusionsThe 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.
Highlights
Lung cancer is the most common cause of cancer death in men and women in the United States [1] with the majority of cases consisting of non-small-cell lung cancer (NSCLC)
Quality assurance of contouring is essential for a successful multi-institutional clinical trial
Dose constraints for radiotherapy planning were provided to the institutions with a prescription dose of 74Gy to the planning target volume (PTV) and mean lung dose less than 20Gy. 3D conformal, intensity-modulated radiation therapy (IMRT) or volumetricmodulated arc therapy (VMAT) were allowed as planning techniques
Summary
Lung cancer is the most common cause of cancer death in men and women in the United States [1] with the majority of cases consisting of non-small-cell lung cancer (NSCLC). Radiation therapy plays an important role in the treatment of NSCLC. Three-dimensional (3D) images are utilized to accurately delineate patient anatomy. Conformal treatment techniques such as intensity-modulated radiation therapy (IMRT) and volumetricmodulated arc therapy (VMAT) are utilized to deliver the prescribed dose to the planning target volume (PTV) while minimizing dose to organs at risk (OAR). Dose-volume histograms (DVH) are often used in treatment planning to evaluate the plan quality. The dose distribution of conformal radiotherapy plans is very dependent on the contours delineated on patient anatomy
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