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SUVmax of incidental colorectal polyps on PET/cT and its association with histopathological features and dysplasia
Hayrani Kaya1, Abdullah Tokuç2, Pırıl Akıncıoğlu2
1Department of Internal Medicine, Akdeniz University, Antalya, Turkey.
Background:
This retrospective single-center study examined whether PET/CT-derived SUVmax is associated with histopathological subtype and dysplasia grade in incidental colorectal polyps, and whether it can predict advanced colorectal neoplasia. The cohort included patients imaged for non-gastrointestinal indications, suspected colorectal malignancy, or prior colorectal cancer. "Incidental" denotes focal uptake anatomically distinct from the primary or suspected pathology.
Methods:
Patients who underwent FDG PET/CT and colonoscopy (within three months) at Akdeniz University Hospital between 2015 and 2020 were screened. In total, 126 patients with focal colorectal uptake and histopathologically confirmed polyps were included; nine (7.1%) had adenocarcinoma at the FDG-avid site. SUVmax was measured using a 3D region of interest. Pathology followed the 2019 WHO classification. Advanced neoplasia was defined as adenocarcinoma or advanced adenoma (≥10 mm, villous/tubulovillous histology, or high-grade dysplasia).
Results:
Median SUVmax was 11.0 (IQR 7.9-17.2) and was higher in advanced than non-advanced neoplasia (13.00 vs. 8.05; p < 0.001). SUVmax correlated with lesion size (ρ = 0.407; p < 0.001) and was higher in villous/tubulovillous adenomas (p = 0.004) and high-grade dysplasia (p = 0.002). After adjustment for age, sex, and localization, SUVmax was associated with advanced neoplasia (OR 1.217 per unit; 95% CI 1.090-1.359; p < 0.001), but not after adding lesion size (OR 0.936; p = 0.141), which remained strongly associated (OR 9.811 per cm; p = 0.003). An SUVmax cutoff ≥12.3 was associated with advanced neoplasia (OR 9.329; 95% CI 3.040-28.632; p < 0.001). Additional PET-negative lesions (36 patients, 28.6%) were smaller (p < 0.001) and less often high-grade dysplasia or carcinoma (20.0% vs. 54.3%; p = 0.004).
Conclusion:
SUVmax reflects histopathological severity in incidental colorectal polyps, but its association with advanced neoplasia was not independent of lesion size. The 12.3 cutoff is exploratory and requires prospective multicenter validation. FDG negativity does not exclude significant pathology; three adenocarcinomas occurred among PET-negative lesions.
