title: Ability of 18F-FDG PET/CT to diagnose recurrent colorectal cancer in patients with elevated CEA concentrations.
abstract: OBJECTIVE
  Elevated levels of serum carcinoembryonic antigen (CEA) in patients with colorectal cancer (CRC) during follow-up suggest recurrence, which can be visualized by (18)F-FDG PET/CT. Since the magnitude of CEA elevation reflects cancer volume, the ability of PET/CT to detect recurrence in patients with only mildly elevated CEA might be limited. However, the accuracy of PET/CT in detecting recurrence associated with elevated CEA has not been fully assessed. We retrospectively evaluated the diagnostic performance of (18)F-FDG PET/CT postoperatively relative to CEA levels among patients with CRC.
  
  
  METHODS
  We visually assessed 75 PET/CT evaluations of 57 postoperative patients with CEA >5.0 ng/ml. Tumor volumes were also determined using image analysis software. The final diagnosis was confirmed based on histopathological findings, or at least on 6 months of clinical follow-up.
  
  
  RESULTS
  Two lung cancers were excluded and we finally analyzed data from 73 of the 75 PET/CT evaluations. Recurrences were diagnosed in 54 (prevalence 74%). The sensitivity and specificity of PET/CT to detect recurrence was 50/54 (93%) and 14/19 (74%), respectively. The positive and negative predictive values were 91 and 78%, respectively, and the positive and negative likelihood ratios were 3.52 and 0.10, respectively. Values for the sensitivity of PET/CT were 88 and 95%, and those for specificity were 78 and 70%, at serum CEA concentrations of 5-10 and >10 ng/ml, respectively. Serum CEA (r = 0.500, p < 0.001) significantly correlated with cancer volumes.
  
  
  CONCLUSIONS
  The present findings showed that (18)F-FDG PET/CT could accurately detect recurrent CRC irrespective of the elevated CEA concentration.
authors.affiliation: Department of Radiology, Japan Self-Defense Forces Central Hospital, Tokyo, Japan.
authors.forename: Yukishige
authors.initials: Y
authors.lastname: Kyoto
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Momose
authors.forename: Chisato
authors.initials: C
authors.lastname: Kondo
authors.forename: Michio
authors.initials: M
authors.lastname: Itabashi
authors.forename: Shingo
authors.initials: S
authors.lastname: Kameoka
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Kusakabe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002272:Carcinoembryonic Antigen / Q000097:blood*; D015179:Colorectal Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012008:Recurrence; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden
chemical_list: D002272:Carcinoembryonic Antigen; D019788:Fluorodeoxyglucose F18