Purpose: Pancreatic adenocarcinoma is one of the cancers with the worst prognosis. The only chance for survival requires early detection, before the disease has spread. Abdominal CT examination is the mainstay of pancreatic imaging. The aim of this study was to assess the overall frequency of undetected pancreatic adenocarcinoma on CT examinations, compare the frequency on portal and pancreatic or triphasic CT examinations, and to evaluate the imaging signs of missed tumors.
Methods: Consecutive pancreatic adenocarcinoma patients were retrospectively collected using a computerized search in our department’s Radiological Information System (RIS) (12/2011-12/2015). Patients with abdominal or chest CT examinations performed up-to a year prior the diagnosis were included. Frequency of missed cancers was evaluated (number of CT examinations with missed cancer/number of CT examinations with either a new diagnosis of cancer or missed cancer) for the entire cohort and separately for portal phase and pancreatic/triphasic CT examinations. Fisher`s exact test evaluated statistical difference in missed detection rate between portal phase and pancreatic/triphasic CT examinations. Two radiologists retrospectively analyzed in consensus the CT examinations of missed cancers and registered radiological signs suggesting the presence of tumors.
Results: Overall 172 patients with a diagnosis of pancreatic cancer on CT examination were retrieved. 114/172 (66.3%) of the examinations were pancreatic or tri-phasic CT protocols, 49/172 (28.5%) were portal phase CT protocols and 10/172 (5.8%) were non-contrast CT. The overall frequency of missed cancers was 6/172 (3.5%). The frequency of missed cancers was significantly higher in portal phase CT examinations as compared to pancreatic/triphasic CT examinations [5/49 (10.2%) vs. 1/117 (0.8%), p=0.009]. The following CT signs were registered in missed cancer cases: 3 cases of small hypodense lesions, 2 cases with peri-pancreatic fat stranding, 1 case of dilated pancreatic duct with cut-off sign and 1 case with peri-pancreatic lymphadenopathy.
Conclusion: Pancreatic adenocarcinoma is undetected in 10.2% of portal phase CT examinations. Pancreatic or triphasic CT protocols should be used liberally in the appropriate clinical scenarios. Radiologists should be attentive to small hypodense lesions, dilated pancreatic ducts with cut-off sign and peri-pancreatic findings.
