Early Postoperative FDG-PET-CT Imaging Results in a Relevant Upstaging in the pN2 Subgroup of Stage III Colorectal Cancer Patients

Introduction: Clinical practice guidelines regarding follow-up in patients after curative resection of colorectal cancer (CRC) vary widely. Current follow-up recommendations do not include additional postoperative imaging before starting adjuvant treatment in any patients. We evaluated the potential benefit of our institutional approach, recommending ¹⁸fluor-deoxy-glucose (FDG)-positron emission tomography (PET)-computed tomography (CT) imaging in CRC stage III patients with ≥4 locoregional lymph node metastases (pN2).

Patients and methods: Our study included all patients from a single center with complete resection of a pT1-4, pN2, cM0 CRC. All patients were considered free of distant metastases on the basis of preoperative CT imaging of the chest, abdomen, and pelvis. The main objective of the present study was to assess the proportion of patients with changes of therapeutic management (defined as any other treatment than the preplanned adjuvant chemotherapy) because of the results of additional postoperative FDG-PET-CT imaging.

Results: Fifty patients (22 female/28 male) were included; the median age was 64 years (range, 37-78 years). Previously undiagnosed metastatic disease resulting in a change of the therapeutic management was detected using postoperative FDG-PET-CT imaging in 7 patients (14.0%; 95% confidence interval, 5.8%-26.7%). The number needed to screen to detect new or previously occult metastases was 7 (7 of 50).

Conclusion: To our knowledge, this is the first study to evaluate the role of an additional postoperative FDG-PET-CT scan before adjuvant treatment in patients with completely resected CRC with ≥4 lymph node metastases (pT1-4, pN2) and without distant metastases on preoperative CT imaging (cM0). Postoperative FDG-PET-CT imaging represents a valuable tool for the detection of new macrometastases in the subgroup of pN2 cM0 CRC patients. The low number needed to screen for consequent therapeutic changes is clinically relevant and should be further evaluated.