The Use of 18-fluorodeoxyglucose (FDG) Positron Emission Tomography in the Staging of Pancreatic Ductal Adenocarcinoma (PDAC)

Abstract

Introduction: The use of FDG-PET in the staging of PDAC is subject to debate. We evaluated the utility of FDG-PET/CT in the detection of distant disease in PDAC patients. Methods: Between 2010 and 2019, we evaluated 699 patients with a diagnosis of PDAC in our multidisciplinary pancreas program; 63 (9%) patients had an FDG-PET/CT. Of these, 29 patients had their FDG-PET/CT and a standard staging CT performed within a 3-month period. Each study was scored by an experienced blinded radiologist along T-, N-, and M-staging criteria. The scores between FDG-PET/CT and CT were compared. Kappa statistics(K) were calculated to estimate inter-study variability. Results: Twenty-nine patients had an FDG-PET/CT and a CT within a median time of 25 days. The median age of diagnosis was 67+9 years old; 12 patients(41.4%) had biopsy-proven metastatic disease. Median CA 19-9 level was 615 U/L. Among modalities of treatment, 21 patients(72.4%) had neoadjuvant chemotherapy, 5 patients(17.2%) had surgical resection, 4 patients(13.8%) had radiation, and 4 patients(13.8%) had adjuvant chemotherapy. FDG avidity was seen in 82.8% of primary tumors with an average standardized uptake value of 9.85. One-year and five-year survival rate of this cohort is 72.4% and 3.4%, respectively. Inter-study variability demonstrated no agreement for T-staging(K= -0.06, p-value=0.49), minimal agreement for N-staging(K= 0.257; p-value = 0.05) and no agreement for M-staging(K= 0.076, p-value = 0.58) between FDG-PET/CT and CT scans. T-staging was the most discordant. FDG-PET/CT upstaged 5 patients(17.2%). Conclusion: There is a high degree of discordance between FDG-PET/CT and CT for staging PDAC, suggesting complementarity between modalities.