Accuracy of 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography for Detection of Recurrent or Metastatic Colorectal Carcinoma in Patients with Rising Carcinoembryonic Antigen Levels

Abstract

Objective: A rise in carcinoembryonic antigen level is commonly encountered during follow-up of patients with colorectal carcinoma. This study aimed to evaluate the diagnostic performance of 18 F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) studies for detection of recurrent or metastatic colorectal carcinoma in patients with rising carcinoembryonic antigen levels. Methods: Patients with colorectal carcinoma in clinical remission with rising carcinoembryonic antigen levels who underwent PET/CT in Prince of Wales Hospital, Hong Kong from 2008 to 2011 were included. Patient demographics, carcinoembryonic antigen levels, and clinical follow-up data were recorded. Outcomes were determined by histopathological findings or at least 12-month follow-up. Results: Forty-two PET/CT studies of 37 patients (16 men and 21 women; mean [standard deviation] age, 65.8 [11.6] years) were included. Carcinoembryonic antigen levels ranged from 1.8 to 45 µg/l (9 patients had normal carcinoembryonic antigen levels of <5 µg/l, but serial carcinoembryonic antigen measurements showed a rising trend). Among the 42 events, 23 (55%) had a positive final diagnosis. The sensitivity, specificity, and positive and negative predictive values of PET/CT for recurrence or metastases were 91.3%, 89.5%, 91.3%, and 89.5%. Conclusion: 18 F-FDG PET/CT is a useful imaging modality to evaluate recurrence or metastases in patients with colorectal carcinoma in clinical remission but showing rising carcinoembryonic antigen levels.