Value of 18-fluorodeoxyglucose positron emission tomography in the management of patients with cystic tumors of the pancreas

Objective To assess the reliability of 18-fluorodeoxyglucose positron emiss ion tomography (18-FDG PET) in distinguishing benign from malignant cystic lesions of the pancreas. Summary Background Data The preoperative differential diagnosis of cystic l esions of the pancreas remains difficult: the most important point is to id entify malignant or premalignant cysts that require resection. 18-FDG PET i s a new imaging procedure based on the increased glucose metabolism by tumo r cells and has been proposed for the diagnosis and staging of pancreatic c ancer. Methods During a 4-year period, 56 patients with a suspected cystic tumor o f the pancreas underwent 18-FDG PET in addition to computed tomography scan ning, serum CA 19-9 assay, and in some instances magnetic resonance imaging or endoscopic retrograde cholangiopancreatography. The 18-FDG PET was anal yzed visually and semiquantitatively using the standard uptake value. The a ccuracy of 18-FDG PET and computed tomography was determined for preoperati ve diagnosis of a malignant cyst. Results Seventeen patients had malignant tumors. Sixteen patients (94%) sho wed 18-FDG uptake with a standard uptake value of 2.6 to 12.0. Twelve patie nts (70%) were correctly identified as having malignancy by computed tomogr aphy, CA 19-9 assay, or both. Thirty-nine patients had benign tumors: only one mucinous cystadenoma showed increased 18-FDG uptake (standard uptake va lue 2.6). Five patients with benign cysts showed computed tomography findin gs of malignancy. Sensitivity, specificity, and positive and negative predi ctive values for 18-FDG PET and computed tomography scanning in detecting m alignant tumors were 94%, 97%, 94%, and 97% and 65%, 87%, 69%, and 85%, res pectively, Conclusions 18-FDG PET is more accurate than computed tomography in identif ying malignant pancreatic cystic lesions and should be used, in combination with computed tomography and tumor markers assay, in the preoperative eval uation of patients with pancreatic cystic lesions. A positive result on 18- FDG PET strongly suggests malignancy and, therefore, a need for resection; a negative result shows a benign tumor that may be treated with limited res ection or, in selected high-risk patients, with biopsy, follow-up, or both.