Clinical significance of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in the follow-up of colorectal cancer: Searching off approaches increasing specificity for detection of recurrence
Objective: Nearly 40% of colorectal cancer (CRC) recur within 2 years after resection of primary tumor. Imaging with fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is the most recent modality and often applied for the evaluation of metastatic spread during the follow-up period. Our goal was to study in CRC the diagnostic importance of 18F-FDG-PET/CT data of maximum standardized uptake value (SUVmax), total lesion glycolysis (TLG) and the difference of SUVmax on dual-time imaging.
Subjects and Methods: We examined the SUVmax value of lesions on control or restaging 18F-FDG-PET/CT of 53 CRC patients. All increased SUVmax values were confirmed by colonoscopy or histopathology. We compared PET/CT results with conventional imaging modalities (CT, MRI) and tumor markers (carbohydrate antigen 19-9 (Ca 19-9), carcinoembryonic antigen (CEA)).
Results: Mean SUVmax was 6.9±5.6 in benign group, 12.7±6.1 in malignant group. Mean TLG of malign group and benign group were 401 and 148, respectively. 18F-FDG-PET/CT was true positive in 48% of patients with normal Ca 19-9 or CEA levels and true negative in 10% of cases with elevated Ca 19-9 or CEA. CT or MRI detected suspicious malignancy in 32% of the patients and 18F-FDG-PET/CT was true negative in 35% of these cases. We found the most important and striking statistical difference between benign and recurrent disease for TLG.
Conclusion: Although SUVmax is a strong metabolic parameter (p=0.008), TLG seems the best predictor in recurrence of colorectal cancers (p=0.001). They are increasing the specificity of 18F-FDG-PET/CT.