Clinical value of dual-phase 18F-FDG PET/CT for differentiating pancreatic cancer from pancreatitis

Abstract

Objective To investigate the value of dual-phase 18F-FDG PET/CT for differentiating pancreatic cancer from pancreatitis. Methods Dual-phase 18F-FDG PET/CT scanning was prospectively performed on patients with suspicious pancreatic lesions. Patients with solid focal pancreatic lesions proved by histopathology or clinical follow-up were enrolled and divided into 3 groups according to the maximum diameter of the focus: ≤2.0 cm (group A), >2.0 cm and ≤ 4.0 cm (group B), >4.0 cm (group C). SUVmax at (60±10) min and (120±15) min after FDG injection was defined as early and delayed SUVmax (SUVearly and SUVdelayed), respectively, and retention index (RI) was calculated. The differences of SUVearly, SUVdelayed and RI between pancreatic cancer and pancreatitis were analyzed with Mann-Whitney u test. ROC curve was used to determine the optimal cutoff values of the above three parameters and corresponding diagnostic efficiencies were obtained. The AUC was compared with MedCalc software. Results A total of 196 patients (152 pancreatic cancers and 44 pancreatic inflammatory lesions) with solid focal pancreatic lesions were enrolled. The AUC of SUVdelayed was significantly larger than that of SUVearly (0.83 vs 0.79, z=3.64, P 0.05). The SUVearly, SUVdelayed and RI of pancreatic cancers were all higher than those of pancreatitis in group A and B (z values: from -4.59 to -3.00, all P 3.6 combined with RI > 0 for diagnosing pancreatic cancer were higher than those of SUVearly > 3.6: 96.4%(27/28) vs 75.0%(21/28), 95.6%(43/45) vs 82.2%(37/45). The AUC of SUVdelayed was significantly larger than that of SUVearly in group B (0.81 vs 0.77, z=2.06, P<0.05). The optimal cutoff value of SUVdelayed in group B was 5.3, with the corresponding sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 84.4%(65/77), 13/19, 91.5%(65/71), 52.0%(13/25) and 81.2%(78/96), respectively. RI of pancreatic cancers was significantly higher than that of pancreatitis (25.0%(15.8%-35.7%) vs 14.4%(4.6%-18.7%), z=-2.39, P<0.05) in group C. The optimal cutoff value of RI in group C was 19.0%, with the corresponding sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 68.1%(32/47), 7/8, 97.0%(32/33), 31.8%(7/22) and 70.9%(39/55). Conclusions The SUVdelayed and RI of dual-phase 18F-FDG PET/CT might be useful for diagnosis of pancreatic tumors. SUVearly > 3.6 combined with RI >0 could be helpful to improve the diagnostic sensitivity and accuracy in patients with the maximum diameter of lesions ≤2.0 cm. The diagnostic value of SUVdelayed might be better than that of SUVearly in patients with the maximum tumor diameter of >2.0 cm and ≤4.0 cm. Only RI could be used for diagnosing pancreatic tumors in patients with the maximum tumor diameter > 4.0 cm. Key words: Pancreatic neoplasms; Pancreatitis; Diagnosis, differential; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose