title: The role of 18F-FDG PET/CT in detecting colorectal cancer recurrence in patients with elevated CEA levels.
abstract: BACKGROUND
  In this study we aimed to define the success of fluorine-18 (18F) fluorodeoxyglucose (FDG) PET/computed tomography (PET/CT) in detecting recurrent disease in our patient group with colorectal cancer (CRC) and elevated carcinoembryonic antigen (CEA) levels.
  
  
  METHODS
  Patients who had a previous diagnosis of CRC were searched retrospectively in our PET center database. Seventy-six 18F-FDG PET/CT studies between October 2006 and December 2010 of 69 patients (25 women, 44 men; mean age: 61.61 ± 4.1 years) with elevated CEA levels were evaluated. 18F-FDG PET/CT findings and concurrent abdominopelvic contrast-enhanced computed tomography (ceCT) findings were compared with histopathological findings and/or clinical follow-up data as the 'gold standard'.
  
  
  RESULTS
  In the patient-based analysis, the sensitivity and specificity of 18F-FDG PET/CT in the detection of disease recurrence were calculated as 97 and 61%, respectively. A statistically significant difference was found in frequencies of positive and negative 18F-FDG PET/CT findings between patients with or without recurrent disease by gold standard (P<0.05). There was no correlation between patients' serum CEA levels and lesions' maximum standardized uptake values (P=0.85). The sensitivity and specificity of ceCT were computed as 51 and 60%, respectively. In the evaluation of separate patient groups, although the sensitivity and specificity of 18F-FDG PET/CT were calculated as 100 and 60% in the group whose CEA level elevation was less than two-fold (5-9.9 ng/ml), these were 100 and 75% in the group with CEA elevation less than three-fold (10-14.9 ng/ml) and 95 and 62% in the group with elevation more than three-fold (≥ 15 ng/ml). The sensitivity and specificity of 18F-FDG PET/CT were computed as 98 and 85% in the lesion-based evaluation. The sensitivity and specificity of ceCT were 73 and 86%, respectively.
  
  
  CONCLUSIONS
  18F-FDG PET/CT is a safe imaging method that can be used in the determination of CRC recurrence in patients with elevated CEA levels, regardless of the CEA level.
authors.affiliation: Department of Nuclear Medicine, Faculty of Medicine, Ankara University, Ankara, Turkey.
authors.forename: Elgin
authors.initials: E
authors.lastname: Ozkan
authors.forename: Cigdem
authors.initials: C
authors.lastname: Soydal
authors.forename: Mine
authors.initials: M
authors.lastname: Araz
authors.forename: Kemal Metin
authors.initials: KM
authors.lastname: Kir
authors.forename: Erkan
authors.initials: E
authors.lastname: Ibis
mesh_terms: D000368:Aged; D002272:Carcinoembryonic Antigen / Q000097:blood; D015179:Colorectal Neoplasms / Q000097:blood / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009364:Neoplasm Recurrence, Local / Q000097:blood / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
chemical_list: D002272:Carcinoembryonic Antigen; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18