Endosonography (EUS), EUS-guided Fine Needle Aspiration (FNA) and 18- Fluorodeoxyglucose Positron Emission Tomography (18-FDG PET) in the evaluation of Pancreatic Cystic Tumors (PCTs)

Introduction: The widespread use of high quality cross-sectional abdominal imaging has dramatically increased the detection of pancreatic cystic tumors (PCTs), classified as benign, potentially malignant (PM) or malignant (M). Based on the principle of high tissue metabolism and 18-FDG uptake in M-cells, 18-FDG PET was reported to be useful in distinguishing M- from non-malignant (NM-) PCTs. Aim: To prospectively evaluate the diagnostic yield of 18-FDG PET compared to EUS and EUS-FNA in the evaluation of PCTs. Methods: Single center study. From January 2002 to November 2004, 39 patients with PCTs were prospectively evaluated: 4 patients were excluded (no histological confirmation); 35 patients (17 ♀, 18 ♂; median age 64 [35–88] yrs) were included. EUS (n=31) was performed prior to 18-FDG PET (n=35). PCTs with an associated mass were considered M by EUS. EUS-FNA cytology results were reported as negative (benign, atypical or suspicious cells) or positive (M-cells), and 18-FDG PET as low (negative) or high (positive) probability for malignancy. A cancer diagnosis was established by M-cells on EUS-FNA or surgery. The performance characteristics of EUS, EUS-FNA and 18-FDG PET in diagnosing M-PCTs were evaluated. Results: Of 35 patients with tissue diagnosis, 10 (28.6%) had cancer (1 mucinous cystadenocarcinoma, 9 M-IPMN), while 25 had NM-PCTs (5 mucinous cystadenoma, 15 IPMN, 5 pseudocysts). The sensitivity, specificity, PPV, NPV and accuracy of (a) EUS morphology were 78%, 95%, 87.5%, 91% and 90%; (b) EUS-FNA were 89%, 100%, 100%, 95% and 97%; (c) 18-FDG PET were 70%, 88%, 70%, 88% and 83% respectively (table 1). Conclusion: In this series, EUS and EUS-FNA was more accurate than 18-FDG PET in differentiating M- from NM-PCTs. Further studies are needed to assess the role of 18-FDG PET in the evaluation of PCTs before adopting it as part of the diagnostic algorithm.

		M-PCTs	NM-PCTs
EUS	Positive	7	1
(n=30)	Negative	2	20
EUS-FNA	Positive	8	0
(n=29)	Negative	1	20
18-FDG PET	Positive	7	3
(n=35)	Negative	3	22