title: Assessment of tumor recurrence in patients with colorectal cancer and elevated carcinoembryonic antigen level: FDG PET/CT versus contrast-enhanced 64-MDCT of the chest and abdomen.
abstract: OBJECTIVE
  The purpose of this study was to compare FDG PET/CT and contrast-enhanced 64-MDCT of the chest, abdomen, and pelvis in the detection of tumor recurrence in patients with colorectal cancer and an elevated level of carcinoembryonic antigen (CEA).
  
  
  METHODS
  A retrospective analysis included 50 patients (31 men, 19 women; mean age, 61 years; range, 28-89 years) with 55 clinical events of elevated or increasing CEA level who underwent FDG PET/CT and MDCT for suspected tumor recurrence.
  
  
  RESULTS
  Recurrent or metastatic disease was found in 36 of 55 events (65.5%) of elevated CEA. Fifty-four of 61 tumor sites suspected as tumor recurrence with any imaging technique were found to be local recurrence or metastatic colorectal cancer at final analysis. The other seven sites were one separate malignant tumor (small lymphocytic lymphoma) and six benign lesions. Diagnosis was based on histopathologic findings (n = 27) or clinical and imaging findings (n = 35) during a median follow-up period of 12 months (range, 6-31 months). One site of tumor recurrence was missed prospectively at both MDCT and PET/CT. On an event-based analysis, the sensitivity of PET/CT and MDCT was 97.3% and 70.3% (p = 0.002); the specificity of both techniques was 94.4% (p = 1.0). In a tumor site-based analysis, the sensitivities of PET/CT and MDCT were 98.1% and 66.7% (p < 0.0001), and the specificities were 75% and 62.5% (p = 0.56). Tumors correctly identified with PET/CT and missed with MDCT were local recurrence in the presacral space (n = 5), metastatic subcentimeter lymph nodes (n = 4), peritoneal deposits (n = 3), and recurrences at the periphery of radiofrequency ablated metastatic lesions of the liver (n = 2) and in the abdominal wall (n = 1), liver (n = 1), and uterine cervix (n = 1).
  
  
  CONCLUSIONS
  FDG PET/CT has higher sensitivity than MDCT in the identification of sites of recurrent and metastatic disease in patients with colorectal cancer and an elevated CEA level. The two techniques appear to have similar specificity.
authors.affiliation: Department of Medical Imaging, Princess Margaret Hospital, University Health Network, 610 University Ave., Ste. 3-960, Toronto, ON, M5G 2M9 Canada.
authors.forename: Ur
authors.initials: U
authors.lastname: Metser
authors.forename: John
authors.initials: J
authors.lastname: You
authors.forename: Sean
authors.initials: S
authors.lastname: McSweeney
authors.forename: Marc
authors.initials: M
authors.lastname: Freeman
authors.forename: Aaron
authors.initials: A
authors.lastname: Hendler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002272:Carcinoembryonic Antigen / Q000097:blood; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging*; D011857:Radiographic Image Interpretation, Computer-Assisted; D011860:Radiography, Abdominal; D013902:Radiography, Thoracic; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D014055:Tomography, Emission-Computed / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D002272:Carcinoembryonic Antigen; D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18