Clinical impact of 18F-FDG-PET in the suspicion of recurrent colorectal cancer based on asymptomatically elevated serum level of carcinoembryonic antigen (CEA) in Taiwan

Background/Aims: To retrospectively evaluate the impact of 18F-fluorodeoxy-glucose-positron emission tomography (FDG-PET) to detect recurrent colorectal cancer based on asymptomatically elevated tumor marker level of carcinoembryonic antigen (CEA). Methodology: Whole-body FDG-PET was performed in 50 patients suspected of having recurrent colorectal cancer and asymptomatically increased serum level of CEA (> 5ng/mL), but other negative or equivocal imaging modality results. A blood sample was drawn in each case for CEA assay on the same day as the FDG-PET. The final diagnosis of recurrent colorectal cancer was established by operation/biopsy histopathological findings or clinical follow-up longer than 1 year by additional morphologic imaging techniques. Results: Among the 50 patients, the final diagnosis of recurrent colorectal cancer was established in 64 lesions of 45 patients. FDG-PET could accurately detect 62 lesions but missed 2 false-negative lesions. In addition, there were 2 false-positive lesions. On a lesion-based analysis, the diagnostic sensitivity and positive predictive value of FDG-PET was 96.9%. There were 2 patients with false-negative lesions and 2 patients with false-positive lesions. Therefore, FDG-PET findings could lead to successful surgical resection in 41 (82.0%) patients. In addition, on a patient-based analysis, the diagnostic sensitivity and positive predictive value of FDG-PET was 95.3%. Conclusions: FDG-PET is a useful technique for detecting recurrent colorectal cancer suspected by asymptomatically elevated serum level of CEA and has an important clinical impact on the management in patients with suspected recurrent colorectal cancer.