Accurate detection of recurrent colorectal carcinoma remains a clinical challenge. Positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (¹⁸FDG) is an imaging technique that allows direct evaluation of cellular metabolism. ¹⁸F-fluorodeoxyglucose PET was compared to computed tomography (CT) and CT portography for staging metastatic colorectal carcinoma.

Twenty-four patients previously treated for colorectal carcinoma who had suspected recurrence to the liver underwent an ¹⁸FDG PET scan of the entire body. All patients had either a CT scan of the abdomen (n = 17), a CT portogram (n = 18), or both (n = 11). The final diagnosis was obtained by tissue pathology in 19 patients and clinical follow-up in 5 patients.

A total of 60 suspicious lesions were identified. Of the 55 intrahepatic lesions, 39 were malignant and 16 were benign. Of the 5 extrahepatic lesions, 4 were malignant. The ¹⁸FDG PET imaging had a higher accuracy (93%) than CT and CT portography (both 76%) in detecting metastatic disease to the liver, and detected unsuspected extrahepatic recurrence in 4 patients. Although the sensitivity of ¹⁸FDG PET (90%) was slightly lower than that of CT portography (97%), the specificity was much higher (100% versus 9%), including postsurgical sites. ¹⁸FDG PET altered surgical plans in 6 (25%) of 24 patients.

¹⁸FDG PET is extremely useful in staging patients with suspected metastatic colorectal carcinoma to the liver.