Aim: The purpose of this prospective study was to investigate the role of 2-(fluorine-18)-fluoro-2-deoxy-D-glucose (18F-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.
Material and 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 18F-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, 18F-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, 18F-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 18F-FDG PET/CT have 100% accuracy in revealing recurrent disease.
Conclusion: 18F-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 18F-FDG in detecting recurrence.
Departments of aNuclear Medicine
bRadiology, Evangelismos Hospital
cDepartment of Clinical Therapeutics, Athens University, Medical School, Athens, Greece
Correspondence to Emmanouil Panagiotidis, MD, MSc, PhD, Department of Nuclear Medicine, General Hospital Evangelismos, Ipsilantou 45-47, Athens 10 676, Greece Tel: +30 210 7201365; fax: +30 210 7203005; e-mail: firstname.lastname@example.org
Received January 30, 2014
Accepted February 24, 2014