Endoscopic ultrasonography in differentiating pancreatic cancer coexisting with chronic pancreatitis compared with other imaging examinations

Background:

It is intrinsically difficult to diagnose pancreatic cancer in the background of chronic pancreatitis (CP) because the malignancy may coexist, precede, or follow CP. Endoscopic ultrasonography (EUS) has been shown to be very accurate in the diagnosis and staging of pancreatic cancer.

Aim:

To determine the value of EUS in differentiating pancreatic cancer coexisting with CP by obtaining long-term follow-up information.

Methods:

We retrospectively and prospectively studied, from our CP database (between January 1997 and August 2007), 514 patients who fulfilled the diagnostic criteria of CP. Chronic pancreatitis (CP) was diagnosed on the basis of a typical history and the presence of any of the following findings: (1) typical CP histology of an adequate surgical pancreatic specimen; 2) pancreatic calcification confirmed by imaging examination; and (3) moderate-to-marked pancreatic ductal lesions on pancreatography obtained by endoscopic retrograde or magnetic resonance pancreatography (Cambridge classification). Patients with a follow-up period of less than two years, a diagnosis of pancreatic cancer established during the first two years of follow-up, or diagnosed within two years of CP diagnosis were diagnosed as pancreatic cancer coexisting with CP. Imaging examination included EUS, computer tomography (CT), magnatic resonance imaging (MRI), magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangio-pancreatography ERCP. Patients performed by EUS were identified and then the patients with suspicious features of pancreatic cancer found by EUS, MRI/MRCP, CT and ERCP but did not showed by the other three imaging examinations were identified, respectively. Patients were seen as a regular follow up as an outpatient at least once a year, or in an unscheduled visit (as outpatients or hospitalized) when the disease became symptomatic or with complications.

Results:

A total of 445 patients were followed up successfully. One-hundred thirteen patients were performed by EUS, including 11 cases were diagnosed as pancreatic cancer coexisting with CP (Group 1) and 102 cases were thought with CP only (Group 2) at the last follow-up time. The rate of suspicion of pancreatic cancer found by EUS in Group 1 was significantly higher than the rate in Group 2 (36.4% (4/11) vs. 5.9% (6/96), P=0.008). Suspicion features of pancreatic cancer included inhomogeneous or hypoechoic echo zone or mass, with/without irregular borders. The rate of suspicious features of pancreatic cancer showed by other imaging examinations in Group 1 was equal to the rate in Group 2 (MRI/MRCP: 14.3% vs. 2.9% P=0.258; CT: 0% vs. 3.1%, P=1.000; ERCP: 0% vs. 1.2% P=1.000).

Conclusion:

EUS had a superior role in differentiating pancreatic cancer coexisting with CP and should be considered as the initial diagnostic modality in patients with CP.