Pancreatic cyst diagnosis: PET/CT outperforms CT and MRI

¹⁸F-FDG PET/CT is a highly useful method for characterizing suspicious pancreatic cystic lesions particularly in patients who have inconclusive findings after undergoing multidetector row CT and/or MRI exams according to a study from Finland published online in the Journal of Nuclear Medicine. The imaging capabilities of CT and MRI are enabling radiologists to identify a dramatically increasing number of incidental cystic findings in the pancreas. In fact, one 2011 study determined that incidentally found pancreatic cysts were found in 45% of abdominal MRI examinations.¹ However, preoperative diagnoses are difficult, and surgical resections are associated with high risks of co-morbidities.

The study’s lead author, Saila Kauhanen, M.D., of the Turku University Hospital’s Division of Digestive Surgery and Urology, and colleagues conducted a study to evaluate which imaging technique is best suited for the assessment of a pancreatic cystic lesion and to assess the impact of ¹⁸F-FDG PET/CT on the clinical management of patients identified as having pancreatic cysts. They hypothesized that ¹⁸F-FDG PET combined with contrast-enhanced CT is a more accurate imaging method than contrast-enhanced CT or MRI alone. Their study compared the results of conventional imaging methods with those of ¹⁸F-FDG PET/CT in a series of 31 consecutive patients with a pancreatic cystic lesion.

Each patient had undergone a CT, MRI, and contrast-enhanced ¹⁸F-FDG PET/CT within a six week period between June 2011 and November 2013. Of the 31 patients, six had malignant lesions; the remainder were benign. Surgical resection was performed for all main duct type intraductal papillary mucinous neoplasia and for branch-duct type lesions greater than 3 cm at follow-up, symptomatic, septal thickening, or with mural nodules at imaging. Diagnosis was based on histopathology and operative findings.

After analysis, the accuracy of contrast-enhanced ¹⁸F-FDG PET/CT was 94%, compared to 87% for MRI and 77% for CT. PET/CT had a sensitivity of 100% and a positive predictive value (PPV) of 75% in the differential diagnosis of malignant and benign pancreatic cystic lesions. The authors noted that its major limitations are false-negative results for borderline and in-situ tumors, and false positive uptakes in areas of lesion-associated pancreatitis. However, they recommend its use in the evaluation of diagnostically challenging pancreatic cysts.

REFERENCES

1. Girometti R, Intini S, Brondani G, et al. Incidental pancreatic cysts on 3D turbo spin echomagnetic resonance cholangiopancreatography: prevalence and relation with clinical and imaging features. Abdominal Imaging. 2011;36:196-205.
2. Kauhanen S, Rinta-Kiikka I, Kemppainen J et al. The diagnostic accuracy study of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT), multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI) in the diagnosis of pancreatic cysts: a prospective single center study. J Nucl Med. Published online June 4, 2015.