The role of fluorine-18-fluorodeoxyglucose (FDG) dual-head gamma camera coincidence imaging in patients with colorectal cancer and unexplained rising levels of carcinoembryonic antigen (CEA)

Background: ¹⁸F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET) has been shown to be of high diagnostic accuracy in recurrent colorectal cancer (CRC). However, FDG assessment is precluded in many patients due to the limited number of PET scanners. SPECT systems in coincidence mode is an alternative. Aims: To determine the role of dual-head gamma camera FDG coincidence imaging (DHC-FDG) in patients with CRC and unexplained rising carcinoembryonic antigen (CEA) levels. Materials: Thirty-seven patients were enrolled. Final diagnosis was based on histology and/or clinical and imaging follow- up of at least one year. Results: Lesion-based analysis - Seventy-one suspected tumor sites were analyzed. Sensitivity of FDG was 85%, PPV 93%, and accuracy 79%. Patients-based analysis - DHC-FDG differentiated patients with and without tumor with sensitivity 79%, specificity 88%, PPV 96%, NPV 54% and accuracy 82%. Based on the FDG findings, nine patients (24%) were referred for a surgery with a curative intent. Conclusion: DHC-FDG is of clinical value in patients with CRC and unexplained raising CEA.