Diagnostic usefulness of FDG PET for pancreatic mass lesions

The purpose of this study was to investigate the feasibility of [F-18]2-deo xy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) in patients with a pancreatic mass by comparing the results with those of X-ray compute d tomography (CT) and magnetic resonance (MR) imaging. Methods: Eighty-six patients with pancreatic lesions, included 65 malignant tumors and 21 benig n masses (55 masses were proven histologically and the others were diagnose d clinically), were studied. The diagnostic factors of CT and MR imaging we re evaluated, and those of FDG PET were also evaluated for malignant and be nign masses by visual interpretation and quantitative interpretation with t he standardized uptake value (SUV) and SUV gluc which was designed to reduc e the effects of a high blood sugar level. Visual interpretations were eval uated only in FDG PET images, and quantitative interpretations were evaluat ed by referring to CT and/or MR imaging. The correlation between SUV and th e degree of histological differentiation in pancreatic ductal adenocarcinom a was investigated. Results: Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for CT imaging we re 91, 62, 88, 68 and 84%, and for MR imaging 78, 70, 88, 54 and 76%, respe ctively. In visual interpretation of FDG PET images, the sensitivity, speci ficity, PPV, NPV and accuracy were 82, 81, 93, 59 and 81%, respectively. Si gnificant differences between malignant and benign lesions existed in SUV a nd SUV gluc (p < 0.0001, each). With the cutoff value of SUV as 2.1 and SUV gluc as 2.2, the accuracy of diagnosis was maximal. With that cutoff value , the sensitivity, specificity, PPV, NPV and accuracy for SUV were 89, 76, 92, 70 and 86%, and for SUV gluc 91, 76, 92, 73 and 87%, respectively. The sensitivity and NPV of SUV gluc were higher than those of SUV, which sugges ts that SUV gluc may be more useful in reducing the number of overlooked ma lignant tumors. The specificity and PPV of FDG PET were superior to those o f CT and MR imaging. There were no significant differences between the SUVs of moderately differentiated adenocarcinomas and those of well differentia ted adenocarcinomas. Conclusion: To improve the diagnostic procedure for cl assifying masses, FDG PET with not only SW but also SUV corrected by the bl ood sugar level is required in addition to morphological diagnosis by CT an d/or MR imaging.