title: Dual-phase 18F-FDG PET/CT imaging in the characterization of pancreatic lesions: does it offer prognostic information?
abstract: OBJECTIVE
  The primary aim of our prospective study was to evaluate the usefulness of dual-phase F-fluoro-deoxy-glucose PET/computed tomography (F-FDG PET/CT) in the characterization of pancreatic masses. The secondary aim was to assess whether delayed imaging revealed any prognostic information.
  
  
  METHODS
  Fifty patients with periampullary or pancreatic masses on conventional imaging were included in this study. Early and delayed PET/CT was performed, followed by pathological examination in all patients. PET/CT parameters including uptake pattern, SUVearly, SUVdelayed, lesion to background ratio (L/B), and retention index (RI) were assessed for their ability to differentiate benign from malignant lesions. Patients with malignant lesions were followed up for a median duration of 26 months. The association of 11 variables with survival was analyzed by univariate and multivariate methods.
  
  
  RESULTS
  Thirty-one patients had malignant lesions and 19 had benign lesions. The mean SUVearly, L/B, SUVdelayed, and RI between the malignant and benign lesions were statistically significant. The F-FDG uptake pattern of the lesions had higher sensitivity (93.5%) and specificity (100%) compared with RI (cutoff 25.7%) (84 and 37%, respectively) for diagnosing malignancy (P<0.05). In univariate analysis both RI (>18.7%) and tumor size (>2.6 cm) predicted significantly poor survival, whereas in multivariate analysis RI (P=0.04) was the only predictor of poor survival.
  
  
  CONCLUSIONS
  Dual-phase F-FDG PET/CT is not useful in characterizing pancreatic masses as it cannot differentiate benign from malignant lesions, and focal uptake on early PET imaging is the best indicator of malignancy. A possible benefit in performing a delayed scan is that a high RI (>18.7) can predict poor survival and hence may be useful in treatment planning.
authors.affiliation: Departments of aNuclear Medicine & PET bGastroenterology cCytology & Gynaecological Pathology dHistopathology eGeneral Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Sampath
authors.initials: S
authors.lastname: Santhosh
authors.forename: Bhagwant R
authors.initials: BR
authors.lastname: Mittal
authors.forename: Deepak
authors.initials: D
authors.lastname: Bhasin
authors.forename: Surinder S
authors.initials: SS
authors.lastname: Rana
authors.forename: Anish
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Radhika
authors.initials: R
authors.lastname: Srinivasan
authors.forename: Ritambhra
authors.initials: R
authors.lastname: Nada
authors.forename: Rajesh
authors.initials: R
authors.lastname: Gupta
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D016019:Survival Analysis
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18