title: The prognostic value of baseline (18)F-FDG PET/CT in steroid-naïve large-vessel vasculitis: introduction of volume-based parameters.
abstract: OBJECTIVE
  The aim of this study was to analyse if the result of a baseline (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT scan, in large-vessel vasculitis (LVV) patients, is able to predict the course of the disease, not only in terms of presence/absence of final complications but also in terms of favourable/complicated progress (response to steroid therapy, time to steroid suspension, relapses, etc.).
  
  
  METHODS
  A total of 46 consecutive patients, who underwent (18)F-FDG PET/CT between May 2010 and March 2013 for fever of unknown origin (FUO) or suspected vasculitis (before starting corticosteroid therapy), were enrolled. The diagnosis of LVV was confirmed in 17 patients. Considering follow-up results, positive LVV patients were divided into two groups, one characterized by favourable (nine) and the other by complicated progress (eight), on the basis of presence/absence of vascular complications, presence/absence of at least another positive PET/CT during follow-up and impossibility to comply with the tapering schedule of the steroid due to biochemical/symptomatic relapse. Vessel uptake in subjects of the two groups was compared in terms of intensity and extension. To evaluate the extent of active disease, we introduced two volume-based parameters: "volume of increased uptake" (VIU) and "total lesion glycolysis" (TLG). The threshold used to calculate VIU on vessel walls was obtained by the "vessel to liver" ratio by means of receiver-operating characteristic analysis and was set at 0.92 × liver maximum standardized uptake value in each patient.
  
  
  RESULTS
  Measures of tracer uptake intensity were significantly higher in patients with complicated progress compared to those with a favourable one (p < 0.05). Measures of disease extension were even more significant and TLG emerged as the best parameter to separate the two groups of patients (p = 0.01).
  
  
  CONCLUSIONS
  This pilot study shows that, in LVV patients, the combined evaluation of the intensity and the extension of FDG vessel uptake at diagnosis can predict the clinical course of the disease, separating patients with favourable or complicated progress.
authors.affiliation: PET/CT Center - Nuclear Medicine Department, Ospedale Civile di Legnano, Via Papa Giovanni Paolo II, 1, 20025, Legnano (MI), Italy.|Department of Health Sciences, University of Milan, Milan, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Dellavedova
authors.affiliation: PET/CT Center - Nuclear Medicine Department, Ospedale Civile di Legnano, Via Papa Giovanni Paolo II, 1, 20025, Legnano (MI), Italy.
authors.forename: M
authors.initials: M
authors.lastname: Carletto
authors.affiliation: Internal Medicine Department, Ospedale Civile di Legnano, Legnano, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Faggioli
authors.affiliation: Internal Medicine Department, Ospedale Civile di Legnano, Legnano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sciascera
authors.affiliation: Department of Health Sciences, University of Milan, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Del Sole
authors.affiliation: Internal Medicine Department, Ospedale Civile di Legnano, Legnano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Mazzone
authors.affiliation: PET/CT Center - Nuclear Medicine Department, Ospedale Civile di Legnano, Via Papa Giovanni Paolo II, 1, 20025, Legnano (MI), Italy. lsmaffioli@yahoo.com.
authors.forename: L S
authors.initials: LS
authors.lastname: Maffioli
mesh_terms: D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000368:Aged; D001167:Arteritis / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed
chemical_list: D000305:Adrenal Cortex Hormones; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18F-FDG PET/CT; Large-vessel vasculitis; Prognosis; Volume-based parameters