Multiparameter diagnostic model based on (18)F-FDG positron emission tomography and serological examination for differentiating focal autoimmune pancreatitis from pancreatic ductal adenocarcinoma

BACKGROUND: (18)F-fluorodeoxyglucose positron emission tomography-computerized tomography ((18)F-FDG PET-CT) has demonstrated high sensitivity in the diagnosis of autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC), while also exhibiting the ability to distinguish AIP from PDAC lesions. The objective of this investigation was to assess the efficacy of multiparametric (18)F-FDG PET with serological examination for distinguishing focal AIP (f-AIP) from PDAC. METHODS: A total of 127 patients (43 with f-AIP and 84 with PDAC) who received (18)F-FDG PET-CT before treatment were retrospectively included in the cohort study conducted at two centers, Beijing Friendship Hospital and Chinese PLA General Hospital, from January 2015 to December 2021. The baseline characteristics and clinical data were collected. The metabolism parameters of (18)F-FDG PET, including maximum standardized uptake value (SUVmax), tumor-to-normal liver SUV ratio (SUVR), mean SUV (SUVmean), total lesion glycolysis (TLG), and metabolic tumor volume (MTV) were evaluated. The area under the receiver operating characteristic (ROC) curve was used to evaluate the differential diagnostic efficacy. The diagnostic efficacy improvement was assessed through the integrated discriminatory improvement (IDI), net reclassification improvement (NRI), and DeLong test. RESULTS: Serum immunoglobulin G4 (IgG4) >280 mg/dL, carbohydrate antigen 19-9 (CA19-9) <85 U/mL, and metabolic parameters differed significantly between patients with f-AID and PDAC. The ROC curve analysis of MTV showed the highest differentiating diagnostic value [sensitivity =0.814, 95% confidence interval (CI): 0.661–0.911; specificity =0.893, 95% CI: 0.802–0.947; area under the curve (AUC) =0.890, 95% CI: 0.820–0.957]. The combined diagnostics model of serum IgG4 >280 mg/dL, CA19-9 <85 U/mL, and MTV resulted in the highest AUC of 0.991 (95% CI: 0.978–1.000; sensitivity =0.953, 95% CI: 0.829–0.992; specificity =0.964, 95% CI: 0.892–0.991). CONCLUSIONS: The multiparameter diagnostic model based on (18)F-FDG PET and serological examination has excellent clinical value in the differential diagnosis of f-AID and PDAC.