title: High-risk CTV delineation for cervix brachytherapy: Application of GEC-ESTRO guidelines in Australia and New Zealand.
abstract: BACKGROUND
  Image-based brachytherapy for cervical cancer using MRI has been implemented in Australia and New Zealand. The aims of this study were to measure variability in High-risk CTV (HR-CTV) delineation and evaluate dosimetric consequences of this.
  
  
  METHODS
  Nine radiation oncologists, one radiation therapist and two radiologists contoured HR-CTV on 3T MRI datasets from ten consecutive patients undergoing cervical brachytherapy at a single institution. Contour comparisons were performed using the Dice Similarity Coefficient (DSC) and Mean Absolute Surface Distance (MASD). Two reference contours were created for brachytherapy planning: a Simultaneous Truth and Performance Level Estimation (STAPLE) and a consensus contour (CONSENSUS). Optimized plans (8 Gy) for both these contours were applied to individual participant's contours to assess D90 and D100 coverage of HR CTV. To compare variability in dosimetry, relative standard deviation (rSD) was calculated.
  
  
  RESULTS
  Good concordance (mean DSC≥0.7, MASD≤5 mm) was achieved in 8/10 cases when compared to the STAPLE reference and 6/10 cases when compared to the CONSENSUS reference. Greatest variation was visually seen in the cranio-caudal direction. The average mean rSD across all patients was 27% and 34% for the STAPLE HR-CTV D90 and D100, respectively, and 28% and 35% for the CONSENSUS HR-CTV D90 and D100. Delineation uncertainty resulted in an average dosimetric uncertainty of ±1.5-1.6 Gy per fraction based on an 8 Gy prescribed fraction.
  
  
  CONCLUSIONS
  Delineation of HR-CTV for cervical cancer brachytherapy was consistent amongst observers, suggesting similar interpretation of GEC-ESTRO guidelines. Despite the good concordance, there was dosimetric variation noted, which could be clinically significant.
authors.affiliation: Cancer Therapy Centre, Liverpool Hospital, Liverpool, New South Wales, Australia.|South Western Sydney Clinical School, University of NSW, Sydney, New South Wales, Australia.
authors.forename: Shalini K
authors.identifier: http://orcid.org/0000-0001-8075-6219
authors.initials: SK
authors.lastname: Vinod
authors.affiliation: Cancer Therapy Centre, Liverpool Hospital, Liverpool, New South Wales, Australia.|South Western Sydney Clinical School, University of NSW, Sydney, New South Wales, Australia.
authors.forename: Karen
authors.initials: K
authors.lastname: Lim
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia.|Ingham Institute of Applied Medical Research, Liverpool Hospital, Liverpool, New South Wales, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Bell
authors.affiliation: Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Veera
authors.affiliation: Cancer Therapy Centre, Liverpool Hospital, Liverpool, New South Wales, Australia.
authors.forename: Lucy
authors.initials: L
authors.lastname: Ohanessian
authors.affiliation: Cancer Therapy Centre, Liverpool Hospital, Liverpool, New South Wales, Australia.
authors.forename: Ewa
authors.initials: E
authors.lastname: Juresic
authors.affiliation: Department of Radiology, Liverpool Hospital, Liverpool, New South Wales, Australia.
authors.forename: Nira
authors.initials: N
authors.lastname: Borok
authors.affiliation: Department of Radiation Oncology, Royal Brisbane & Women's Hospital, Brisbane, Queensland, Australia.|School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Chan
authors.affiliation: Genesis Cancer Care, Perth, Western Australia, Australia.|School of Surgery, University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Raphael
authors.initials: R
authors.lastname: Chee
authors.affiliation: Crown Princess Mary Cancer Centre, Westmead Hospital, Westmead, New South Wales, Australia.|Nepean Clinical School, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Viet
authors.initials: V
authors.lastname: Do
authors.affiliation: Department of Radiation Oncology, Calvary Mater Hospital, Newcastle, New South Wales, Australia.
authors.forename: Geetha
authors.initials: G
authors.lastname: Govindarajulu
authors.affiliation: Department of Radiation Oncology, Calvary Mater Hospital, Newcastle, New South Wales, Australia.
authors.forename: Swetha
authors.initials: S
authors.lastname: Sridharan
authors.affiliation: Wellington Blood & Cancer Centre, Wellington Hospital, Wellington, New Zealand.
authors.forename: Carol
authors.initials: C
authors.lastname: Johnson
authors.affiliation: School of Medicine, University of NSW, Sydney, New South Wales, Australia.|Department of Radiology, Prince of Wales Hospital, Randwick, New South Wales, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Moses
authors.affiliation: Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Van Dyk
authors.affiliation: Cancer Therapy Centre, Liverpool Hospital, Liverpool, New South Wales, Australia.|South Western Sydney Clinical School, University of NSW, Sydney, New South Wales, Australia.|Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia.|Ingham Institute of Applied Medical Research, Liverpool Hospital, Liverpool, New South Wales, Australia.
authors.forename: Lois
authors.initials: L
authors.lastname: Holloway
mesh_terms: D001315:Australia; D001918:Brachytherapy / Q000379:methods*; D002584:Cervix Uteri / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000379:methods*; D009520:New Zealand; D017410:Practice Guidelines as Topic; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*
keywords: brachytherapy; cervix cancer; interobserver variability; radiotherapy