Clinical Impact of Preoperative 18F-FDG PET/CT in Localized Colon Cancer: A Prospective Study with Long-Term Follow-Up

The present investigation evaluated the potential added value of preoperative ¹⁸F-FDG PET/CT over conventional primary staging procedures in patients diagnosed with presumed non-metastatic colonic cancer (CC). In addition, the study assessed the prognostic implications of ¹⁸F-FDG uptake in the primary tumor, with an average follow-up of 15 years. Patients newly diagnosed with apparently localized CC were prospectively recruited and underwent ¹⁸F-FDG PET/CT scanning before surgery. SUVmax, SUVpeak, TLG, and MTV were quantified for each colonic lesion and analyzed for their prognostic potential. A total of 48 patients participated in the study. Histopathological examination of surgical specimens identified 103 colonic lesions, comprising 58 invasive adenocarcinomas, 4 in situ adenocarcinomas, 3 high-grade dysplastic adenomas, and 38 low-grade dysplastic adenomas. Per-lesion diagnostic performance for primary colonic tumor detection yielded sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 78%, 97%, 98%, and 73% for conventional workup, versus 94%, 87%, 92%, and 89% for ¹⁸F-FDG PET/CT. A statistically significant difference was observed solely in sensitivity between the two approaches. PET imaging revealed 10 additional pathological colonic lesions in 7 patients. SUVmax, SUVpeak, and TLG values differed significantly between invasive adenocarcinomas, in situ adenocarcinomas, and high-grade dysplasia lesions when compared with low-grade dysplasia. A significant distinction was also noted between pT1-pT2 and pT3-pT4 adenocarcinomas. On a patient-based basis, nodal staging performance showed sensitivity, specificity, PPV, and NPV of 22%, 84%, 44%, and 65% for contrast-enhanced CT (CECT) and 33%, 90%, 67%, and 70% for ¹⁸F-FDG PET/CT, without reaching statistical significance. Furthermore, PET/CT revealed occult metastatic disease and one synchronous primary lung cancer in four patients. In total, ¹⁸F-FDG PET/CT supplied supplementary diagnostic information in 11 of the 48 patients (23%). Uptake intensity of ¹⁸F-FDG in the primary tumor did not predict nodal involvement or distant metastases. Stratification of disease-free survival according to median values of SUVmax, SUVpeak, TLG, and MTV revealed no significant differences. In summary, preoperative ¹⁸F-FDG PET/CT serves as a valuable tool for detecting colonic lesions missed by conventional assessments, especially when colonoscopy cannot be completed. It reliably identifies distant metastases but shows limited accuracy in N staging. Largely due to the modest cohort size, the quantitative evaluation of 18F-FDG uptake in the primary lesion demonstrated no association with recurrence or disease-free survival and therefore provided no substantial prognostic information.