Undetected Pancreatic Adenocarcinoma on CT: Frequency According to CT Scan Protocol

Purpose: CT is a main diagnostic modality for detecting pancreatic adenocarcinoma. This study aims to assess the frequency of missed pancreatic adenocarcinoma on CT scans according to different CT protocols. Methods: : Consecutive pancreatic adenocarcinoma patients were retrospectively collected (12/2011-12/2015). Patients with abdominal CT scans performed up-to a year prior to cancer diagnosis were included. Two radiologists registered in consensus the presence and radiological signs of missed cancers. The frequency of missed cancers was compared between portal and pancreatic/triphasic CT protocols. Results: : Overall, 180 CT scans of pancreatic adenocarcinoma patients were retrieved. 126/180 (70.0%) were pancreatic/triphasic protocols and 54/180 (30.0%) were portal protocols. The overall frequency of missed cancers was 6/180 (3.3%). The frequency of missed cancers was higher in portal CT protocols compared to pancreatic/triphasic protocols: 5/54 (9.3%) vs. 1/126 (0.8%), p=0.01. CT signs of missed cancers included: 3 cases of small hypodense lesions, 2 cases with peri-pancreatic fat stranding, 1 case of dilated pancreatic duct with a cut-off sign. Conclusion: The frequency of missed pancreatic adenocarcinoma is higher on portal CT protocols. Physicians should consider the cancer miss rate on different CT protocols.