Utility of (18) F-FDG PET/CT and CECT in conjunction with serum CA 19-9 for detecting recurrent pancreatic adenocarcinoma

Purpose: The roles of different cross-sectional imaging in evaluating the recurrence of pancreatic adenocarcinoma are not well established. We evaluated the utility of ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and contrast-enhanced computed tomography (CECT) in the diagnosis of recurrent pancreatic adenocarcinoma in conjunction with the tumor marker CA 19-9. Methods: We retrospectively reviewed the records of patients who underwent CECT and FDG PET/CT along with serum CA 19-9 measurement as a follow-up or on a clinical suspicion of recurrent disease after initial surgery for pancreatic adenocarcinoma. Two observers blinded to the other imaging modality results retrospectively reviewed and interpreted the images in consensus using a three-point scale (negative, equivocal, or positive). Pathologic analysis by biopsy or further clinical and radiologic follow-up determined the true status of the suspected recurrences. The imaging results were compared with CA 19-9 levels and true disease status. Results: Thirty-nine patients were included in the study. Thirty-three patients (85%) had proven recurrent cancer and six patients (15%) had no evidence of disease. Twenty-four patients had elevated CA 19-9 and 15 patients had normal CA 19-9. Sensitivity, specificity, and accuracy for recurrence were 90.9%, 100.0%, and 92.3% for PET/CT and 72.2%, 66.6%, and 71.7% for CECT, respectively. Sensitivity for locoregional recurrence was 94.4% for PET/CT but only 61.1% for CECT. PET/CT detected recurrence in 12 patients who had normal levels of CA 19-9. PET/CT showed lesions not visible on CECT in five (15%) patients. Although the sensitivity and specificity of PET/CT were higher than those of CECT, they were not statistically significant (p = 0.489 and p = 0.1489, respectively). Conclusion: FDG PET/CT has a high sensitivity for pancreatic cancer recurrence. Normal CA 19-9 does not necessarily exclude these recurrences. FDG PET/CT is useful when CECT is equivocal and can detect recurrence in patients with normal CA 19-9.