Evaluation of (pre-)malignant colonic abnormalities: endoscopic validation of FDG-PET findings

The diagnostic accuracy of 2-[(18)F]-fluoro-2-deoxy- D-glucose positron emission tomography (FDG-PET) for the detection of (pre-)malignant lesions of the colon was compared with that of endoscopy. We selected a cohort of 39 patients [13 females and 26 males; mean age 62.3 years standard deviation (SD) 9.6 years] who underwent both FDG-PET and endoscopy (total of 44 procedures) in a 2-year period with a maximum interval between the examinations of 3 months (mean 30 days, SD 28 days). The underlying pathology was colorectal malignancies (24 patients), other malignancies (nine patients) and other disorders (six patients). Follow-up of resected colorectal cancer was the most common reason for the performance of endoscopy. In 19 patients FDG bowel uptake was interpreted as non-physiological, and in 18 patients abnormal findings (adenomatous polyps >3 mm or carcinoma) were detected by endoscopy. Compared with colonoscopy, FDG-PET had a sensitivity of 74% and specificity of 84%. The positive predictive value of FDG-PET was 78%. FDG-PET failed to detect small (diameter 3-10 mm) polyps in four patients. In nine cases abnormal FDG accumulation on PET imaging was the sole reason for performance of an endoscopic procedure. In these cases, endoscopy detected large adenomatous polyps in four patients and carcinomas in two patients, but no abnormalities were detected on endoscopy in the other three patients. There was a good correlation between the location of FDG uptake and endoscopy-positive lesions. FDG-PET is able to detect clinically relevant lesions of the colon. Our study suggests that it can be regarded as a useful adjunct in the non-invasive follow-up of patients with colorectal carcinomas.