Combined SUVmax and localized colonic wall thickening parameters to identify high-risk lesions from incidental focal colorectal F-FDG uptake foci.

OBJECTIVE

To evaluate the detection ability of F-FDG PET/CT for identifying high-risk lesions (high-risk adenomas and adenocarcinoma) from incidental focal colorectal F-FDG uptake foci combining maximum standard uptake value (SUVmax) and localized colonic wall thickening (CWT). The secondary objective was to investigate the factors of missed detection of high-risk adenomas by F-FDG PET/CT.

PATIENTS AND METHODS

A total of 6394 patients who underwent F-FDG PET/CT in our hospital from August 2019 to December 2021 were retrospectively analysed, and 145 patients with incidental focal colorectal F-FDG uptake foci were identified. The optimal cut-off value of SUVmax for F-FDG PET/CT diagnosis of high-risk lesions was determined by receiver operating characteristic (ROC) curves. SUVmax and localized CWT were combined to identify high-risk lesions from incidental focal colorectal F-FDG uptake foci. The characteristics of incidental adenomas detected and high-risk adenomas missed by F-FDG PET/CT were compared.

RESULTS

Of the 6394 patients, 145 patients were found to have incidental focal colorectal FDG uptake foci (2.3%), and 44 patients underwent colonoscopy and pathological examination at the same time. In fact, 45 lesions, including 12 low-risk lesions and 33 high-risk lesions (22 high-risk adenomas, 11 adenocarcinoma), were found by colonoscopy. The area under the ROC curve of SUVmax for low-risk lesions and high-risk lesions was 0.737, and the optimal cut-off value was 6.45 (with a sensitivity of 87.9% and specificity of 58.3%). When SUVmax ≥6.45, the combination of localized CWT parameters has little influence on the sensitivity and specificity of detection; when SUVmax <6.45, the combination of localized CWT parameters can improve the specificity of detection of high-risk lesions, but the sensitivity has little change. In addition, the size of high-risk adenomas discovered incidentally by F-FDG PET/CT was larger than that of high-risk adenomas missed, but there was no significant difference in lesion location, pathological type or intraepithelial neoplasia between the two groups.

CONCLUSIONS

The combination of SUVmax and localized CWT parameters of F-FDG PET/CT helped identify high-risk lesions from incidental focal colorectal F-FDG uptake foci, especially for lesions with SUVmax <6.45. Lesion size may be the only factor in F-FDG PET/CT missing high-risk adenomas.