Rudi Apolle1,2, Steffen Appold1,3, Henk P Bijl4, Pierre Blanchard5, Johan Bussink6, Corinne Faivre-Finn7, Jonathan Khalifa8, Anne Laprie8, Yolande Lievens9, Indira Madani10, Amandine Ruffier5, Dirk de Ruysscher11, Wouter van Elmpt11, Esther G C Troost1,2,3,12,13,14,15. 1. OncoRay - National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf , Dresden , Germany. 2. Helmholtz-Zentrum Dresden - Rossendorf, Institute of Radiooncology - OncoRay , Dresden , Germany. 3. Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden , Dresden , Germany. 4. Department of Radiation Oncology, University Medical Center Groningen , Groningen , The Netherlands. 5. Department of Radiation Oncology, Gustave Roussy Cancer Campus , Villejuif , France. 6. Department of Radiation Oncology, Radboud University Medical Center , Nijmegen , The Netherlands. 7. The Christie NHS Foundation Trust, Division of Cancer Science, The University of Manchester , Manchester , UK. 8. Department of Radiotherapy, Institut Claudius Regaud/Institut Universitaire du Cancer de Toulouse - Oncopole , Toulouse , France. 9. Radiation Oncology Department, Ghent University Hospital and Ghent University , Ghent , Belgium. 10. Department of Radiation Oncology, University Hospital Zürich , Zürich , Switzerland. 11. Department of Radiation Oncology (MAASTRO), GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre , Maastricht , The Netherlands. 12. German Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research Center DKFZ, Heidelberg , Germany. 13. National Center for Tumor Diseases (NCT), Partner Site Dresden, Germany: German Cancer Research Center (DKFZ) , Heidelberg , Germany. 14. Faculty of Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany. 15. Helmholtz Association / Helmholtz-Zentrum Dresden - Rossendorf (HZDR) , Dresden , Germany.
Abstract
Introduction: Inter-observer variability (IOV) in target volume delineation is a well-documented source of geometric uncertainty in radiotherapy. Such variability has not yet been explored in the context of adaptive re-delineation based on imaging data acquired during treatment. We compared IOV in the pre- and mid-treatment setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locoregionally advanced head-and-neck squamous cell carcinoma (HNSCC) and (non-)small cell lung cancer [(N)SCLC]. Material and methods: Five and six observers participated in the HNSCC and (N)SCLC arm, respectively, and provided delineations for five cases each. Imaging data consisted of CT studies partly complemented by FDG-PET and was provided in two separate phases for pre- and mid-treatment. Global delineation compatibility was assessed with a volume overlap metric (the Generalised Conformity Index), while local extremes of IOV were identified through the standard deviation of surface distances from observer delineations to a median consensus delineation. Details of delineation procedures, in particular, GTV to CTV expansion and adaptation strategies, were collected through a questionnaire. Results: Volume overlap analysis revealed a worsening of IOV in all but one case per disease site, which failed to reach significance in this small sample (p-value range .063-.125). Changes in agreement were propagated from GTV to CTV delineations, but correlation could not be formally demonstrated. Surface distance based analysis identified longitudinal target extent as a pervasive source of disagreement for HNSCC. High variability in (N)SCLC was often associated with tumours abutting consolidated lung tissue or potentially invading the mediastinum. Adaptation practices were variable between observers with fewer than half stating that they consistently adapted pre-treatment delineations during treatment. Conclusion: IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the conventional causes of IOV. Consensus guidelines are urgently needed.
Introduction: Inter-observer variability (IOV) in target volume delineation is a well-documented source of geometric uncertainty in radiotherapy. Such variability has not yet been explored in the context of adaptive re-delineation based on imaging data acquired during treatment. We compared IOV in the pre- and mid-treatment setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locoregionally advanced head-and-neck squamous cell carcinoma (HNSCC) and (non-)small cell lung cancer [(N)SCLC]. Material and methods: Five and six observers participated in the HNSCC and (N)SCLC arm, respectively, and provided delineations for five cases each. Imaging data consisted of CT studies partly complemented by FDG-PET and was provided in two separate phases for pre- and mid-treatment. Global delineation compatibility was assessed with a volume overlap metric (the Generalised Conformity Index), while local extremes of IOV were identified through the standard deviation of surface distances from observer delineations to a median consensus delineation. Details of delineation procedures, in particular, GTV to CTV expansion and adaptation strategies, were collected through a questionnaire. Results: Volume overlap analysis revealed a worsening of IOV in all but one case per disease site, which failed to reach significance in this small sample (p-value range .063-.125). Changes in agreement were propagated from GTV to CTV delineations, but correlation could not be formally demonstrated. Surface distance based analysis identified longitudinal target extent as a pervasive source of disagreement for HNSCC. High variability in (N)SCLC was often associated with tumours abutting consolidated lung tissue or potentially invading the mediastinum. Adaptation practices were variable between observers with fewer than half stating that they consistently adapted pre-treatment delineations during treatment. Conclusion: IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the conventional causes of IOV. Consensus guidelines are urgently needed.
Authors: Harald Paganetti; Chris Beltran; Stefan Both; Lei Dong; Jacob Flanz; Keith Furutani; Clemens Grassberger; David R Grosshans; Antje-Christin Knopf; Johannes A Langendijk; Hakan Nystrom; Katia Parodi; Bas W Raaymakers; Christian Richter; Gabriel O Sawakuchi; Marco Schippers; Simona F Shaitelman; B K Kevin Teo; Jan Unkelbach; Patrick Wohlfahrt; Tony Lomax Journal: Phys Med Biol Date: 2021-02-26 Impact factor: 4.174