Predictive value of 18F-fluorodeoxyglucose PET/CT in histological grade of incidental colorectal adenoma

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron-emission tomography/computed tomography (PET/CT) as an imaging modality for the whole body has shown its value in detecting incidental colorectal adenoma. In clinical practice, adenomatous polyps can be divided into three groups: low-grade intraepithelial neoplasia (LGIN), high-grade intraepithelial neoplasia (HGIN) and cancer, which can lead to different clinical management. However, the relationship between the 18F-FDG PET/CT SUVmax and the histological grade of adenomatous polyps is still not established, which is a challenging but valuable task.

This retrospective study included 255 patients with colorectal adenoma (CRA) or colorectal adenocarcinomas (AC) who had corresponding ¹⁸F-FDG uptake incidentally found on PET/CT. The correlations of SUVmax with pathological characteristics and tumor size were assessed. Neoplasms were divided into LGIN, HGIN, and AC according to histological grade. Receiver operating characteristic (ROC) analysis was applied to evaluate the predictive value of the SUVmax-only model and comprehensive models which were established with imaging and clinical predictors identified by univariate and multivariate analysis.

The SUVmax was positively correlated with histological grades (r=0.529, P<0.001). Univariate and multivariate analysis showed that SUVmax was an independent risk factor among all groups except between HGIN and AC. The area under the curves (AUCs) of the comprehensive model for distinguishing between AC and adenoma, LGIN and HIGN, LGIN and AC, and HGIN and AC were 0.886, 0.780, 0.945, 0.733, respectively, which is statistically higher than the AUCs of the SUVmax-only model with 0.812, 0.733, 0.863, and 0.688, respectively.

As an independent risk factor, SUVmax based on ¹⁸F-FDG PET/CT is highly associated with the histological grade of CRA. Thus, ¹⁸F-FDG PET/CT can serve as a noninvasive tool for precise diagnosis and assist in the preoperative formulation of treatment strategies for patients with incidental CRA.