title: Comparison of CT-based volumetric dosimetry with traditional prescription points in the treatment of cervical cancer with PDR brachytherapy.
abstract: BACKGROUND
  The traditional use of two-dimensional geometric prescription points in intracavitary brachytherapy planning for locally advanced cervical cancer is increasingly being replaced by three-dimensional (3D) planning. This study aimed to directly compare the two planning methods to validate that CT planning provides superior dosimetry for both tumour and organs at risk (OARs) in our department.
  
  
  METHODS
  The CT planning data of 10 patients with locally advanced cervical cancer was audited. For each CT dataset, two new brachytherapy plans were created, comparing the dosimetry of conventional American Brachytherapy Society points and 3D-optimised volumes created for the high-risk clinical target volume (HR CTV) and OARs. Total biologically equivalent doses for these structures were calculated using the modified EQD2 formula and comparative dose-volume histogram (DVH) analysis performed.
  
  
  RESULTS
  DVH analysis revealed that for the 3D-optimised plans, the prescription aim of D90 ≥ 100% was achieved for the HR CTV in all 10 patients. However, when prescribing to point A, only 50% of the plans achieved the minimum required dose to the HR CTV. Rectal and bladder dose constraints were met for all 3D-optimised plans but exceeded in two and one of the conventional plans, respectively.
  
  
  CONCLUSIONS
  This study confirms that the regionally relevant practice of CT-based 3D-optimised planning results in improved tumour dose coverage compared with traditional points-based planning methods and also improves dose to the rectum and bladder.
authors.affiliation: Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.
authors.forename: Nicola
authors.identifier: http://orcid.org/0000-0001-6716-8762
authors.initials: N
authors.lastname: Lowrey
authors.affiliation: Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.
authors.forename: Sanna
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Moutrie
authors.affiliation: Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.|School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Chan
authors.affiliation: Department of Radiation Oncology, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia.|School of Medicine, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Robyn
authors.initials: R
authors.lastname: Cheuk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008875:Middle Aged; D011874:Radiometry / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome; D047368:Tumor Burden; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*
keywords: brachytherapy; cervix cancer; computed tomography; dosimetry