title: Does CEA and CA 19-9 combined increase the likelihood of 18F-FDG in detecting recurrence in colorectal patients with negative CeCT?
abstract: OBJECTIVE
  The purpose of this prospective study was to investigate the role of 2-(fluorine-18)-fluoro-2-deoxy-D-glucose ((18)F-FDG) PET/computed tomography (CT) in the diagnosis of recurrent colorectal cancer (CRC) in patients with increased tumor markers and negative contrast-enhanced computed tomography (CeCT) results.
  
  
  METHODS
  Forty-three patients (27 male; median age 66 years, range 31-93 years) with increasing tumor markers and negative CeCT during follow-up for treated CRC underwent (18)F-FDG PET/CT examinations. The serum values of carcinoembryonic antigen (CEA) (n=29) and CA 19-9 (n=20) were normal after completion of treatment, with subsequent increasing concentrations.
  
  
  RESULTS
  Among the 43 patients, (18)F-FDG PET/CT was true positive in 32 (74.4%), false positive in two (4.7%), false negative in one (2.3%), and true negative in eight (1%) patients. On the patient-basis analysis, (18)F-FDG PET/CT had a sensitivity of 97% (confidence interval: 0.82-0.99), a specificity of 80% (0.44-0.96), a positive predictive value of 94% (0.78-0.98), and a negative predictive value of 88% (0.5-0.99). There was no statistically significant correlation between CRC recurrence and CEA and CA19-9 levels (P=0.561 and 0.55, respectively). Only in the group of patients (n=6) with both tumor markers increased did (18)F-FDG PET/CT have 100% accuracy in revealing recurrent disease.
  
  
  CONCLUSIONS
  (18)F-FDG PET/CT is highly sensitive in the diagnosis of recurrent CRC in patients with increasing levels of tumor markers and negative CeCT regardless of the type or level of tumor marker; however, the combination of elevated CEA and CA 19-9 increases the likelihood of (18)F-FDG in detecting recurrence.
authors.affiliation: Departments of aNuclear Medicine bRadiology, Evangelismos Hospital cDepartment of Clinical Therapeutics, Athens University, Medical School, Athens, Greece.
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Panagiotidis
authors.forename: Ioannis E
authors.initials: IE
authors.lastname: Datseris
authors.forename: Phoebe
authors.initials: P
authors.lastname: Rondogianni
authors.forename: Evangelia
authors.initials: E
authors.lastname: Vlontzou
authors.forename: Maria
authors.initials: M
authors.lastname: Skilakaki
authors.forename: Demetrios
authors.initials: D
authors.lastname: Exarhos
authors.forename: Aristotelis
authors.initials: A
authors.lastname: Bamias
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000097:blood*; D014408:Biomarkers, Tumor / Q000097:blood; D002272:Carcinoembryonic Antigen / Q000097:blood*; D015179:Colorectal Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011336:Probability; D012008:Recurrence; D014057:Tomography, X-Ray Computed
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D014408:Biomarkers, Tumor; D002272:Carcinoembryonic Antigen; C578959:carbohydrate antigen 199, human; D019788:Fluorodeoxyglucose F18