Incidental focal colorectal F-18-fluorodeoxyglucose uptake on positron emission tomography/computed tomography
ABSTRACT To assess the clinical significance of incidental focal colorectal (18)F-fluorodeoxyglucose ((18)F-FDG) uptake on (18)F-FDG-positron emission tomography/computed tomography (PET/CT).
The records of all the cases which had undergone colonoscopy after PET/CT within a two weeks interval were reviewed. Adenomas were considered advanced when they were villous, ≥ 10 mm in size, or had high-grade dysplasia. Colorectal cancers and advanced adenomas are collectively referred to as advanced colorectal neoplasms. Receiver-operating characteristic curve analysis was used to determine the significant predictive maximum standardized uptake value (SUVmax) cutoff value for advanced colorectal neoplasms and cancer.
Ninety-five colorectal lesions matched the site of incidental focal colorectal (18)F-FDG uptake on PET/CT and 146 did not. Colonoscopy showed advanced colorectal neoplasms corresponding to the site of (18)F-FDG uptake in 49 of the 95 (51.5%) lesions with incidental uptake. Of the lesions without incidental uptake, only 6 of 146 (4.1%) had advanced colorectal neoplasms on colonoscopy, indicating a statistically significant difference between the two groups (P < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of incidental focal (18)F-FDG uptake in identifying advanced colorectal neoplasms were 89.1%, 75.3%, 51.6%, 95.9%, and 78.4%, respectively. In detecting only CRC, these values were 89.2%, 69.6%, 34.7%, 97.3%, and 72.6%, respectively. The significant SUVmax cutoff value for advanced colorectal neoplasms (area under the curve 0.755, P < 0.001) was 4.35, with a sensitivity, specificity, PPV, NPV, and accuracy of 75.5%, 65.2%, 69.8%, 71.4% and 70.5%, respectively. For CRC, 5.05 was the significant SUVmax cutoff value (area under the curve 0.817, P < 0.001), with a sensitivity, specificity, PPV, NPV, and accuracy of 84.8%, 71.0%, 80.9%, 89.8%, and 75.8%, respectively.
The presence of incidental focal colorectal (18)F-FDG uptake on PET/CT with a SUVmax ≥ 4.35 increases the likelihood of an advanced colorectal neoplasm.
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ABSTRACT: Purpose: Unexpected focal colonic or rectal radiotracer activity is an usual finding in patients subjected to a PET study. The aim of this work has been to evaluate the clinical significance of this finding in the prediction of an existing colorectal malignancy. Material and methods: During the last three years, all patients studied with F-18-FDG PET/CT and PET for oncologic work-up purposes were prospectively surveyed for focal colorectal radiotracer activity. Colonoscopy was performed in all patients with this incidental finding in order to exclude colonic malignancy. CEA level, maximum standardized uptake value (SUVmax), CT findings, colonoscopy findings and histopathological results were prospectively analyzed in all patients. Results: A total of 2290 patients were evaluated, 158 of whom were studied with PET and the remainder with a hybrid PET/CT. Focal FDG colorectal activity was incidentally detected in 27 patients with no previous history of colorectal cancer. Colorectal adenocarcinoma was diagnosed in seven (25.9%) patients. A pre-cancerous lesion was found in eleven patients (40.7%). Eight patients (29.6%) had no macroscopic lesions. One patient was diagnosed with a benign lesion. Any focal activity found in the colon by F-18-FDG PET/CT examination predicts a probability greater than 50% of an underlying malignant or premalignant lesion in the histopathological analysis (logistic regression, p = 0.01), independently of the calculated SUVmax. Conclusion: According to the results of the present study, we recommend the performance of a colonoscopy and biopsy of any suspicious lesions, in all patients with unexpected focal FDG activity found in colon or rectum during a F-18-FDG PET/CT examination.Revista Española de Medicina Nuclear e Imagen Molecular 09/2014; 34(2). DOI:10.1016/j.remn.2014.07.008 · 0.86 Impact Factor
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ABSTRACT: Focal (18)F-fluorodeoxyglucose (FDG) colonic activity can be incidentally seen in positron emission tomography/computed tomography (PET/CT) scans. Its clinical significance is still unclear. The purpose of this study was to assess the significance of focal FDG activity in PET/CT scans by correlating the imaging findings to colonoscopy results, and come up with some guidelines for recommendation of follow-up colonoscopy. A total of 133 patients who underwent both (18)F-FDG PET/CT for different oncological indications and colonoscopy within 3 months were retrospectively studied. Imaging, colonoscopy and pathology results were analyzed. Of the 133 FDG-PET/CT scans, 109/133 (82%) did not show focal colonic FDG activity, and 24/133 (18%) did. Of the 109/133 PET/CTs without focal colonic FDG activity, 109/109 (100%) did not have evidence of colon cancer after colonoscopy and histology. Of the 24/133 PET/CTs with focal colonic FDG activity, 10/24 (42%) had pathologic confirmation of colon cancer and 14/24 (58%) did not have evidence of colon cancer after colonoscopy and histological analysis. Sensitivity was 10/10 (100%), specificity 109/123 (89%), positive predictive value (PPV) 10/24 (42%) and negative predictive value (NPV) 109/109 (100%). Incidental focal (18)FDG activity in PET/CT imaging shows a high sensitivity, specificity and NPV for malignancy, with a not so high PPV of 42%. Although some people would argue that a 42% chance of malignancy justifies colonoscopy, this maybe is not possible in all cases. However, the high sensitivity of the test does not allow these studies to be overlooked. We provide our recommendations as per when to send patients with focal FDG colonic activity to have further characterization with colonoscopy.01/2015; 14(1):25-30. DOI:10.4103/1450-1147.150524