title: Nonsurgical giant cell tumour of the tendon sheath or of the diffuse type: are MRI or 18F-FDG PET/CT able to provide an accurate prediction of long-term outcome?
abstract: OBJECTIVE
  To investigate whether MRI (RECIST 1.1, WHO criteria and the volumetric approach) or (18)F-FDG PET/CT (PERCIST 1.0) are able to predict long-term outcome in nonsurgical patients with giant cell tumour of the tendon sheath or of the diffuse type (GCT-TS/DT).
  
  
  METHODS
  Fifteen "nonsurgical" patients with a histological diagnosis of GCT-TS/DT were divided into two groups: symptomatic patients receiving targeted therapy and asymptomatic untreated patients. All 15 patients were evaluated by MRI of whom 10 were treated, and a subgroup of 7 patients were evaluated by PET/CT of whom 4 were treated. Early evolution was assessed according to MRI and PET/CT scans at baseline and during follow-up. Cohen's kappa coefficient was used to evaluate the degree of agreement between PERCIST 1.0, RECIST 1.1, WHO criteria, volumetric approaches and the reference standard (long-term outcome, delay 505 ± 457 days). The response rate in symptomatic patients with GCT-TS/DT receiving targeted therapy was also assessed in a larger population that included additional patients obtained from a review of the literature.
  
  
  RESULTS
  The kappa coefficients for agreement between RECIST/WHO/volumetric criteria and outcome (15 patients) were respectively: 0.35 (p = 0.06), 0.26 (p = 0.17) and 0.26 (p = 0.17). In the PET/CT subgroup (7 patients), PERCIST was in perfect agreement with the late symptomatic evolution (kappa = 1, p < 0.05). In the treated symptomatic group including the additional patients from the literature the response rates to targeted therapies according to late symptomatic assessment, and PERCIST and RECIST criteria were: 65 % (22/34), 77 % (10/13) and 26 % (10/39).
  
  
  CONCLUSIONS
  (18)F-FDG PET/CT with PERCIST is a promising approach to the prediction of the long-term outcome in GCT-TS/DT and may avoid unnecessary treatments, toxicity and costs. On MRI, WHO and volumetric approaches are not more effective than RECIST using the current thresholds.
authors.affiliation: Department of Nuclear Medicine, IUCT-Oncopole/Institut Claudius Regaud, 31100, Toulouse, France, laurent.dercle@gmail.com.
authors.forename: Laurent
authors.initials: L
authors.lastname: Dercle
authors.forename: Roland
authors.initials: R
authors.lastname: Chisin
authors.forename: Samy
authors.initials: S
authors.lastname: Ammari
authors.forename: Quentin
authors.initials: Q
authors.lastname: Gillebert
authors.forename: Monia
authors.initials: M
authors.lastname: Ouali
authors.forename: Cyril
authors.initials: C
authors.lastname: Jaudet
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Delord
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dierickx
authors.forename: Slimane
authors.initials: S
authors.lastname: Zerdoud
authors.forename: Martin
authors.initials: M
authors.lastname: Schlumberger
authors.forename: Frédéric
authors.initials: F
authors.lastname: Courbon
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D005870:Giant Cell Tumors / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D019275:Radiopharmaceuticals; D013710:Tendons / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18