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

Abstract

We analyzed whether preoperative ¹⁸F-FDG PET/CT adds to conventional primary staging in patients with presumed non-metastatic colonic cancer (CC). The prognostic role of ¹⁸F-FDG uptake in the primary tumor was evaluated after a mean follow-up of 15 years. Patients with a new diagnosis of presumed localized CC were prospectively enrolled and underwent presurgical ¹⁸F-FDG PET/CT. For each colon lesion, SUVmax, SUVpeak, TLG, and MTV were assessed and tested as prognostic factors. Forty-eight patients were included. Post-surgery pathology identified a total of 103 colon lesions, including 58 invasive adenocarcinomas, 4 in situ adenocarcinomas, 3 adenomas with high-grade dysplasia, and 38 adenomas with low-grade dysplasia. Per lesion sensitivity, specificity, positive (PPVs) and negative predictive values (NPVs) for colonic primary tumor detection were 78%, 97%, 98%, and 73% for conventional workup, and 94%, 87%, 92%, and 89% for ¹⁸F-FDG PET/CT. Only sensitivity was significantly different between ¹⁸F-FDG PET/CT and conventional workup. PET detected an additional ten pathological colonic lesions in seven patients. SUVmax, SUVpeak, and TLG showed significant differences between invasive adenocarcinomas, in situ adenocarcinomas, and high-grade dysplasia compared to low-grade dysplasia. There was a statistically significant difference between pT1-pT2 and pT3-pT4 adenocarcinomas. On patient-based analysis, sensitivity, specificity, PPV, and NPV for nodal staging were 22%, 84%, 44%, and 65% for CECT, and 33%, 90%, 67%, and 70% for ¹⁸F-FDG PET/CT, without a statistically significant difference. PET/CT also identified unknown metastatic spread and one synchronous lung cancer in four patients. Overall, ¹⁸F-FDG PETCT had an additional diagnostic value in 11 out of 48 patients (23%). ¹⁸F-FDG uptake of the primary tumor did not predict nodal or distant metastases. The difference in disease-free survival categorized by median SUVmax, SUVpeak, TLG, and MTV was not significant. Finally, preoperative ¹⁸F-FDG PET/CT is valuable in detecting potential colon lesions not visualized by conventional workups, especially in cases of incomplete colonoscopy. It effectively highlights distant metastases but exhibits limitations for N staging. Mainly due to the relatively small sample size, the quantitative analysis of ¹⁸F-FDG uptake in the primary tumor did not reveal any association with recurrence or disease-free survival, adding no significant prognostic information.

Keywords: 18F-FDG; PET/CT; carcinoma; colon; presurgical; staging; surgery.

Figure 1

Presurgical 18F-FDG PET/CT results of 3 patients with presumed localized CC (arrows) showing additional colon lesion or visceral metastasis not visualized at conventional staging (dotted arrows). 57-old year man with (pT3) sigmoid primary (A) and synchronous invasive carcinoma (T2) of left colon (B). 74-old year man with 11 cm (pT3) tumor of the caecum (C), and adenoma with high grade dysplasia of the right colon (D). 46-old year woman with incomplete colonoscopy due to a sigmoid tumoral stenosis (pT3) (E), and right ovary metastasis (F).