Accuracy and economic impact of helical CT and endoscopic ultrasound in the staging of ampullopancreatic tumors

Helical CT (HCT) is an innovative means of abdominal imaging which provides high resolution images of the pancreatic bed. The relative accuracy of HCT and EUS in defining the local resectability of ampullopancreatic tumors is undefined. Methods: From 3/94-11/96 we prospectively evaluated 51 patients with ampullary or pancreatic adenocarcinoma. Patients with metastatic disease were excluded. All patients were evaluated with HCT and EUS. Imaging results were compared with surgical staging and a tumor was defined as resectable when there was no macroscopic or microscopic residual disease. Performance characteristics for HCT and EUS were incorporated into our decision model to estimate the clinical and economic outcomes of alternative staging strategies. Results: 30 of 51 patients were explored with 14 patients undergoing complete resection and 16 patients found to have unresectable disease. HCT correctly identified all resectable tumors but only identified 5 of the 16 unresectable tumors. EUS correctly identified 13 resectable tumors and 12 unresectable tumors. Helical CT EUS Sensitivity (unresectable) 31 % 75% p<0.05 Specificity (unresectable) 100% 93% Positive predictive value 100% 94% Accuracy 63% 83% A staging strategy employing HCT as the only means of detecting locally unresectable disease would result in 27.1 unnecessary surgical explorations per 100 patients staged and cost $140,000 per curative resection while a strategy of HCT followed by EUS would decrease the number of unnecessary surgical explorations to 7.6 per 100 patients staged and reduce the cost per curative resection to $108,000. Conclusions: EUS is more sensitive than HCT in detecting vascular invasion by ampullopancreatic tumors. Based on a high positive predictive value, detection of unresectable disease by HCT obviates the need for further diagnostic imaging. However the addition of EUS when HCT fails to detect unresectable disease reduces the number of unnecessary explorations and is more cost-effective relative to a strategy employing HCT alone.