Detection of relevant colonic neoplasms with PET/CT: promising accuracy with minimal CT dose and a standardised PET cut-off

Abstract

Objective:To determine the performance of FDG-PET/CT in the detection of relevant colorectal neoplasms (adenomas ≥10 mm, with high-grade dysplasia, cancer) in relation to CT dose and contrast administration and to find a PET cut-off.Methods:84 patients, who underwent PET/CT and colonoscopy (n = 79)/sigmoidoscopy (n = 5) for colonic segments, were included in a retrospective study. The accuracy of low-dose PET/CT in detecting mass-positive segments was evaluated by ROC analysis by two blinded independent reviewers relative to contrast-enhanced PET/CT. On a per-lesion basis characteristic PET values were tested as cut-offs.Results:Low-dose PET/CT and contrast-enhanced PET/CT provide similar accuracies (area under the curve for the average ROC ratings 0.925 vs. 0.929, respectively). PET demonstrated all carcinomas (n = 23) and 83% (30/36) of relevant adenomas. In all carcinomas and adenomas with high-grade dysplasia (n = 10) the SUVmax was ≥5. This cut-off resulted in a better per-segment sensitivity and negative predictive value (NPV) than the average PET/CT reviews (sensitivity: 89% vs. 82%; NPV: 99% vs. 98%). All other tested cut-offs were inferior to the SUVmax.Conclusion:FDG-PET/CT provides promising accuracy for colorectal mass detection. Low dose and lack of iodine contrast in the CT component do not impact the accuracy. The PET cut-off SUVmax ≥ 5 improves the accuracy.

Positron emission tomography/computed tomography for optimized colon cancer staging and follow-up.

“…PET/CT readers identified 97-98% of primary tumors, similar to previously reported detection rates [11,34]. In this prospective head-to-head comparison, PET/CT-based M-staging showed robust reproducibility and better specificity and higher total correct classification rate than CT. Organ-specific M-staging accuracies confirm previous findings of overdiagnosis of suspicious lung lesions in CC patients by CT [35], even in a CC cohort displaying a considerably higher prevalence of lung metastases than reported in the literature [36].…”

A Stepwise Approach Using Metabolic Volume and SUVmax to Differentiate Malignancy and Dysplasia From Benign Colonic Uptakes on 18F-FDG PET/CT

“…20 In a study by Gutman et al, 6 SUVmax was 15 T 11.6 for malignancy (n = 3), 12 T 3.7 for HGD (n = 4), 8.8 T 4.9 for LGD (n = 6), and 7.1 T 3.3 in the negative colonoscopic group (n = 7). In another study by Luboldt et al, 10 SUVmax was 12.9 T 6.8 for malignancy (n = 23), 11.6 T 4.1 for HGD (n = 10), 9.7 T 6.9 for LGD (n = 25), and 7.4 T 3.8 for FP (n = 48). These findings are comparable with our result with larger study populations.…”

“…Despite the popular use of maximum standardized uptake value (SUVmax), a quantitative measurement of radioactivity, to help distinguish between benign and malignant lesions, differentiation of colonic malignancy from adenoma or false-positive results (FP) still remains limited. 6,10,13 Metabolic volume (MV) is a novel index in FDG PET. It represents the extent of FDG uptake by tumor tissues and is used for the estimation of gross tumor volume (GTV).…”

Relevance of Incidental Colorectal FDG-PET/CT-Enhanced Lesions

“…In our review all cases had a SUVmax of at least 5. These recommendations were based on personal experience of the physicians responsible and on published data [5,11]. The purpose of these recommendations was to aid in ruling out invasive colorectal cancers.…”