title: Impact of 18F-FDG PET/CT on target volume delineation in recurrent or residual gynaecologic carcinoma.
abstract: BACKGROUND
  To evaluate the impact of 18F-FDG PET/CT on target volume delineation in gynaecological cancer.
  
  
  METHODS
  F-FDG PET/CT based RT treatment planning was performed in 10 patients with locally recurrent (n = 5) or post-surgical residual gynaecological cancer (n = 5). The gross tumor volume (GTV) was defined by 4 experienced radiation oncologists first using contrast enhanced CT (GTVCT) and secondly using the fused 18F-FDG PET/CT datasets (GTVPET/CT). In addition, the GTV was delineated using the signal-to-background (SBR) ratio-based adaptive thresholding technique (GTVSBR). Overlap analysis were conducted to assess geographic mismatches between the GTVs delineated using the different techniques. Inter- and intra-observer variability were also assessed.
  
  
  RESULTS
  The mean GTVCT (43.65 cm3) was larger than the mean GTVPET/CT (33.06 cm3), p = 0.02. In 6 patients, GTVPET/CT added substantial tumor extension outside the GTVCT even though 90.4% of the GTVPET/CT was included in the GTVCT and 30.2% of the GTVCT was found outside the GTVPET/CT. The inter- and intra-observer variability was not significantly reduced with the inclusion of 18F-FDG PET imaging (p = 0.23 and p = 0.18, respectively). The GTVSBR was smaller than GTVCT p ≤ 0.005 and GTVPET/CT p ≤ 0.005.
  
  
  CONCLUSIONS
  The use of 18F-FDG PET/CT images for target volume delineation of recurrent or post-surgical residual gynaecological cancer alters the GTV in the majority of patients compared to standard CT-definition. The use of SBR-based auto-delineation showed significantly smaller GTVs. The use of PET/CT based target volume delineation may improve the accuracy of RT treatment planning in gynaecologic cancer.
authors.affiliation: Division of Radiation Oncology, Geneva University Hospital, Geneva 14 CH-1211, Switzerland. hansjorg.vees@hcuge.ch
authors.forename: Hansjörg
authors.initials: H
authors.lastname: Vees
authors.forename: Nathalie
authors.initials: N
authors.lastname: Casanova
authors.forename: Thomas
authors.initials: T
authors.lastname: Zilli
authors.forename: Hestia
authors.initials: H
authors.lastname: Imperiano
authors.forename: Osman
authors.initials: O
authors.lastname: Ratib
authors.forename: Youri
authors.initials: Y
authors.lastname: Popowski
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
authors.forename: Raymond
authors.initials: R
authors.lastname: Miralbell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D005833:Genital Neoplasms, Female / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging / Q000473:pathology*; D018365:Neoplasm, Residual / Q000000981:diagnostic imaging / Q000473:pathology*; D015588:Observer Variation; D049268:Positron-Emission Tomography; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18