title: Indeterminate lung nodules in cancer patients: pretest probability of malignancy and the role of 18F-FDG PET/CT.
abstract: OBJECTIVE
  The purpose of this study was to determine likelihood of malignancy for indeterminate lung nodules identified on CT comparing two standardized models with (18)F-FDG PET/CT.
  
  
  METHODS
  Fifty-nine cancer patients with indeterminate lung nodules (solid tumors; diameter, ≥5 mm) on CT had FDG PET/CT for lesion characterization. Mayo Clinic and Veterans Affairs Cooperative Study models of likelihood of malignancy were applied to solitary pulmonary nodules. High probability of malignancy was assigned a priori for multiple nodules. Low (<5%), intermediate (5-60%), and high (>60%) pretest malignancy probabilities were analyzed separately. Patients were reclassified with PET/CT. Histopathology or 2-year imaging follow-up established diagnosis. Outcome-based reclassification differences were defined as net reclassification improvement. A null hypothesis of asymptotic test was applied.
  
  
  RESULTS
  Thirty-one patients had histology-proven malignancy. PET/CT was true-positive in 24 and true-negative in 25 cases. Negative predictive value was 78% and positive predictive value was 89%. On the basis of the Mayo Clinic model (n=31), 18 patients had low, 12 had intermediate, and one had high pretest likelihood; on the basis of the Veterans Affairs model (n=26), 5 patients had low, 20 had intermediate, and one had high pretest likelihood. Because of multiple lung nodules, 28 patients were classified as having high malignancy risk. PET/CT showed 32 negative and 27 positive scans. Net reclassification improvements respectively were 0.95 and 1.6 for Mayo Clinic and Veterans Affairs models (both p<0.0001). Fourteen of 31 (45.2%) and 12 of 26 (46.2%) patients with low and intermediate pretest likelihood, respectively, had positive findings on PET/CT for the Mayo Clinic and Veterans Affairs models, respectively. Of 15 patients with high pretest likelihood and negative findings on PET/CT, 13 (86.7%) did not have lung malignancy.
  
  
  CONCLUSIONS
  PET/CT improves stratification of cancer patients with indeterminate pulmonary nodules. A substantial number of patients considered at low and intermediate pretest likelihood of malignancy with histology-proven lung malignancy showed abnormal PET/CT findings.
authors.affiliation: 1 Radiotherapy and Nuclear Medicine Unit, Veneto Institute of Oncology IOV-IRCCS, Padua, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Evangelista
authors.forename: Annalori
authors.initials: A
authors.lastname: Panunzio
authors.forename: Roberta
authors.initials: R
authors.lastname: Polverosi
authors.forename: Fabio
authors.initials: F
authors.lastname: Pomerri
authors.forename: Domenico
authors.initials: D
authors.lastname: Rubello
mesh_terms: D000368:Aged; D003627:Data Interpretation, Statistical; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000175:diagnosis*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18