title: High-risk clinical target volume delineation in CT-guided cervical cancer brachytherapy: impact of information from FIGO stage with or without systematic inclusion of 3D documentation of clinical gynecological examination.
abstract: OBJECTIVE
  The aim of the study was to improve computed tomography (CT)-based high-risk clinical target volume (HR CTV) delineation protocols for cervix cancer patients, in settings without any access to magnetic resonance imaging (MRI) at the time of brachytherapy. Therefore the value of a systematic integration of comprehensive three-dimensional (3D) documentation of repetitive gynecological examination for CT-based HR CTV delineation protocols, in addition to information from FIGO staging, was investigated. In addition to a comparison between reference MRI contours and two different CT-based contouring methods (using complementary information from FIGO staging with or without additional 3D clinical drawings), the use of standardized uterine heights was also investigated.
  
  
  METHODS
  Thirty-five cervix cancer patients with CT- and MR-images and 3D clinical drawings at time of diagnosis and brachytherapy were included. HR CTV(stage) was based on CT information and FIGO stage. HR CTV(stage + 3Dclin) was contoured on CT using FIGO stage and 3D clinical drawing. Standardized HR CTV heights were: 1/1, 2/3 and 1/2 of uterine height. MRI-based HR CTV was delineated independently. Resulting widths, thicknesses, heights, and volumes of HR CTV(stage), HR CTV(stage + 3Dclin) and MRI-based HR CTV contours were compared.
  
  
  RESULTS
  The overall normalized volume ratios (mean ± SD of CT/MRI(ref) volume) of HR CTV(stage) and HR stage + 3Dclin were 2.6 (± 0.6) and 2.1 (± 0.4) for 1/1 and 2.3 (± 0.5) and 1.8 (± 0.4), for 2/3, and 1.9 (± 0.5) and 1.5 (± 0.3), for 1/2 of uterine height. The mean normalized widths were 1.5 ± 0.2 and 1.2 ± 0.2 for HR CTV(stage) and HR CTV(stage + 3Dclin), respectively (p < 0.05). The mean normalized heights for HR CTV(stage) and HR CTV(stage + 3Dclin) were both 1.7 ± 0.4 for 1/1 (p < 0.05.), 1.3 ± 0.3 for 2/3 (p < 0.05) and 1.1 ± 0.3 for 1/2 of uterine height.
  
  
  CONCLUSIONS
  CT-based HR CTV contouring based on FIGO stage alone leads to large overestimation of width and volume. Target delineation accuracy can systematically improve through incorporation of additional information from comprehensive 3D documentation of repetitive gynecological examination in the contouring protocol, and thus help to improve the accuracy of dose optimization in settings with limited access to imaging facilities at the time of brachytherapy. If CT information is only available, minimum 2/3 of uterine height may be a good surrogate for the height of HR CTV.
authors.affiliation: Department of Radiotherapy, Comprehensive Cancer Centre Vienna, Medical University of Vienna , Vienna , Austria.
authors.forename: Neamat
authors.initials: N
authors.lastname: Hegazy
authors.forename: Richard
authors.initials: R
authors.lastname: Pötter
authors.forename: Christian
authors.initials: C
authors.lastname: Kirisits
authors.forename: Daniel
authors.initials: D
authors.lastname: Berger
authors.forename: Mario
authors.initials: M
authors.lastname: Federico
authors.forename: Alina
authors.initials: A
authors.lastname: Sturdza
authors.forename: Nicole
authors.initials: N
authors.lastname: Nesvacil
mesh_terms: D001918:Brachytherapy; D005260:Female; D005500:Follow-Up Studies; D058869:Gynecological Examination; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D009367:Neoplasm Staging; D011379:Prognosis; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D012189:Retrospective Studies; D012307:Risk Factors; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy