FDG PET/CT and Colonoscopy Combine Synergistically in Primary Colorectal Cancer Diagnosis

Background: colonoscopy is the standard for primary colorectal cancer (crc) detection, but is invasive and imperfect. this study aimed to assess the accuracy of 18f-fluorodeoxyglucose (fdg) positron emission tomography/computed tomography (pet/ct) and colonoscopy in the diagnosis of primary crc. methods: a retrospective analysis of all patients identified as undergoing an fdg pet/ct scan and a colonoscopy within six months of each other, with no intervening malignancy treatment, over 12 months in a single university teaching hospital. results: two hundred and sixty-two patients had fdg pet/ct and colonoscopy within six months. 206 were excluded for prior treatment. 56 patients were included; 26 (46%) with confirmed primary crc tumors and 30 (54%) without. multivariate logistic regression analysis indicated that crc diagnosis was more likely when colonoscopy was performed before the fdg pet/ct (or: 21.9, ci 2.6-183) and when crc was diagnosed on fdg pet/ct (or 12.3, ci 3.0-51.0). the roc-auc for fdg pet/ct and colonoscopy was 0.81 (ci 0.70-0.93, p<0.001) and 0.96 (ci 0.90-1.0, p<0.001), respectively. conclusions: colonoscopy is very good and fdg pet/ct is good as diagnostic tests for crc primary diagnosis. together, they facilitated diagnosis in all primary cases of crc. pet/ct should be considered in patients with incomplete colonoscopy where there is suspicion for primary crc.