Performance of integrated FDG PET/contrast-enhanced CT in the diagnosis of recurrent colorectal cancer: Comparison with integrated FDG PET/non-contrast-enhanced CT and enhanced CT

Purpose  The aim of our study was to evaluate the accuracy of integrated positron emission tomography and computed tomography (PET/CT) using ¹⁸F-fluorodeoxyglucose (FDG) with IV contrast for depiction of suspected recurrent colorectal cancer and to assess the impact of PET/contrast-enhanced CT findings on clinical management compared with PET/non-contrast-enhanced CT and CT component. Methods  One hundred seventy patients previously treated for colorectal cancer underwent PET/CT consisting of non-enhanced and contrast-enhanced CT for suspected recurrence. PET/contrast-enhanced CT, PET/non-contrast-enhanced CT and enhanced CT were interpreted by two experienced radiologists by consensus for each investigation. Lesion status was determined on the basis of histopathology, radiological imaging and clinical follow-up for longer than 6 months. Results  Patient-based analysis showed that the sensitivity, specificity and accuracy of PET/contrast-enhanced CT were 93.2 (69/74), 95.8 (92/96) and 94.7% (161/170), respectively, whereas those of PET/non-contrast-enhanced CT were 89.2 (66/74), 94.8 (91/96) and 92.4% (157/170), respectively, and those of enhanced CT were 79.7 (59/74), 93.8 (90/96) and 87.6% (149/170), respectively. Sensitivity and accuracy differed significantly among the three modalities (Cochran’s Q test: p = 0.0004 and p = 0.0001, respectively).The findings of PET/contrast-enhanced CT resulted in a change of management for 64 of the 170 patients (38%) and had an effect on patient management in 12 patients (7%) diagnosed by enhanced CT alone and 4 patients (2%) diagnosed by PET/non-contrast-enhanced CT. Conclusion  Integrated PET/contrast-enhanced CT is an accurate modality for assessing colorectal cancer recurrence and led to changes in the subsequent appropriate therapy.