Effect of clinicopathologic factors on visibility of colorectal polyps with FDG PET.

Abstract

The objective of our study was to clarify which clinicopathologic factors affect the FDG PET visibility of colorectal polyps. We used statistical methods in a retrospective examination of factors affecting the visibility of 87 colorectal polyps in 50 patients who underwent PET for cancer screening. PET depicted 37% (32/87) of polyps. Univariate analysis revealed significant associations between polyp visibility and polyp size, histologic grade (p < 0.001 each), type (p = 0.004), and patient age (p = 0.049) but not sex or polyp location. The visualization rate increased with increases in polyp size (< or = 5 mm, 12%; 6-10 mm, 47%; > or = 11 mm, 59%) and severity of dysplasia (indefinite or low-grade dysplasia, 13%; high-grade dysplasia, 67%; polyp with early carcinoma, 75%) and was higher for pedunculated polyps (59%) than for nonpedunculated polyps (27%). Multivariate analysis showed that histologic grade was the strongest factor (p < 0.001) among three independent factors (histologic grade, type, and age). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for visualization of high-grade or early carcinoma polyps to be removed were 71%, 87%, 78%, 82%, and 80%. Maximum standardized uptake values did not differ significantly between visualized polyps with indefinite or low-grade dysplasia and visualized polyps with high-grade dysplasia or early carcinoma. Histologic grade is the strongest independent factor in FDG PET visibility of colorectal polyps. FDG PET visibility may be helpful for predicting whether a polyp should be removed or observed. FDG PET findings also may suggest the need to alter the treatment of patients with colorectal polyps.