Lauren Bell1, Lois Holloway2, Kjersti Bruheim3, Primož Petrič4, Christian Kirisits5, Kari Tanderup6, Richard Pötter5, Shalini Vinod7, Karen Lim7, Elise Pogson8, Peter Metcalfe9, Taran Paulsen Hellebust10. 1. Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia. Electronic address: lb998@uowmail.edu.au. 2. Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia; Liverpool & Macarthur Cancer Therapy Centres, Liverpool, Australia; Ingham Institute for Applied Medical Research, Liverpool, Australia; South Western Sydney Clinical School, University of New South Wales, Liverpool, Australia; Institute of Medical Physics, University of Sydney, Sydney, Australia. 3. Department of Oncology, Oslo University Hospital, Oslo, Norway. 4. Radiation Oncology Department, National Center for Cancer Care and Research, Doha, Qatar; Division of Radiotherapy, Institute of Oncology, Ljubljana, Slovenia. 5. Department of Radiation Oncology, Comprehensive Cancer Center, Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria. 6. Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark. 7. Liverpool & Macarthur Cancer Therapy Centres, Liverpool, Australia; South Western Sydney Clinical School, University of New South Wales, Liverpool, Australia. 8. Liverpool & Macarthur Cancer Therapy Centres, Liverpool, Australia; Ingham Institute for Applied Medical Research, Liverpool, Australia; South Western Sydney Clinical School, University of New South Wales, Liverpool, Australia. 9. Centre for Medical Radiation Physics, University of Wollongong, Wollongong, Australia; Liverpool & Macarthur Cancer Therapy Centres, Liverpool, Australia; Ingham Institute for Applied Medical Research, Liverpool, Australia. 10. Department of Medical Physics, Oslo University Hospital, Oslo, Norway.
Abstract
PURPOSE: To examine the variability in prescribed dose due to contouring variations in intracavitary image-guided adaptive brachytherapy for cervical cancer. To identify correlations between dosimetric outcomes and delineation uncertainty metrics. METHODS AND MATERIALS: A data set from an EMBRACE sub-study on contouring uncertainties was used, consisting of magnetic resonance images of six patients with cervical cancer delineated by 10 experienced observers (target volumes and organs at risk). Two gold standard contours were generated, an expert consensus and the simultaneous truth and performance level estimation. Plans were individually optimised to all of the contour sets (12 in total). Plans were applied to the gold standard contour sets, and dose volume histogram parameters including D90, D98 and D2cm3 were determined. The variability between plans was assessed. Dose volume histogram parameters and delineation uncertainty metrics were correlated using the Spearman's non-parametric rank correlation. RESULTS: There is a dosimetric variability between observers, patients and the gold standard contour used for analysis. Approximately 3 Gy D90 EQD210 variability (SD) was observed for the CTVHR and 1.2-3.6 Gy D2cm3 EQD23 for the organs at risk. The maximum geometric dimensions of the delineations are most commonly correlated with dosimetry changes. Although the correlations are similar across gold standards, the direction of these correlations differs, indicating that the dosimetric outcomes are dependent on the contour that the plan is optimised to. CONCLUSION: This study highlights the dosimetric differences interobserver uncertainty in contouring can have for cervical cancer brachytherapy. The importance of carefully choosing a gold standard from which to benchmark is reiterated.
PURPOSE: To examine the variability in prescribed dose due to contouring variations in intracavitary image-guided adaptive brachytherapy for cervical cancer. To identify correlations between dosimetric outcomes and delineation uncertainty metrics. METHODS AND MATERIALS: A data set from an EMBRACE sub-study on contouring uncertainties was used, consisting of magnetic resonance images of six patients with cervical cancer delineated by 10 experienced observers (target volumes and organs at risk). Two gold standard contours were generated, an expert consensus and the simultaneous truth and performance level estimation. Plans were individually optimised to all of the contour sets (12 in total). Plans were applied to the gold standard contour sets, and dose volume histogram parameters including D90, D98 and D2cm3 were determined. The variability between plans was assessed. Dose volume histogram parameters and delineation uncertainty metrics were correlated using the Spearman's non-parametric rank correlation. RESULTS: There is a dosimetric variability between observers, patients and the gold standard contour used for analysis. Approximately 3 Gy D90 EQD210 variability (SD) was observed for the CTVHR and 1.2-3.6 Gy D2cm3 EQD23 for the organs at risk. The maximum geometric dimensions of the delineations are most commonly correlated with dosimetry changes. Although the correlations are similar across gold standards, the direction of these correlations differs, indicating that the dosimetric outcomes are dependent on the contour that the plan is optimised to. CONCLUSION: This study highlights the dosimetric differences interobserver uncertainty in contouring can have for cervical cancer brachytherapy. The importance of carefully choosing a gold standard from which to benchmark is reiterated.
Authors: Michael V Sherer; Diana Lin; Sharif Elguindi; Simon Duke; Li-Tee Tan; Jon Cacicedo; Max Dahele; Erin F Gillespie Journal: Radiother Oncol Date: 2021-05-11 Impact factor: 6.901