Background: Autoimmune pancreatitis (AIP) is a peculiar type of chronic pancreatitis that responds dramatically to steroid therapy. To date, there are no worldwide consensus criteria for AIP. Different criteria with institutional preference (HISORt, revised Kim, and the revised Japanese criteria) are being used to diagnose AIP, and there is a controversy on the inclusion of steroid responsiveness in the diagnostic criteria. In contrast to the HISORt and revised Kim criteria, the revised Japanese criteria do not include steroid responsiveness as a diagnostic component.
Aims: This study was performed to evaluate whether "a two-week steroid trial and subsequent assessment of its response" is a useful diagnostic tool for the differentiation of AIP from pancreatic cancer. We also wanted to discover the surgical and clinical outcome for a patient who followed our treatment algorithm based on the steroid responsiveness.
Design: Prospective study.
Patients and methods: From January 2004 to June 2007, in the setting of clinically suspected AIP, twenty-two consecutive patients with atypical imaging for AIP while not meeting the classic imaging criteria for pancreatic cancer were challenged to undergo two weeks of steroid therapy (0.5mg/kg of oral prednisolone per day). After the two-week steroid trial, steroid responsiveness was assessed based on a marked improvement of the main pancreatic ductal narrowing and a reduction of the pancreatic mass. The steroid trial was continued in the case of positive steroid responsiveness, whereas surgical exploration was conducted in the case of negative steroid responsiveness. Final diagnosis was made by surgical exploration or long-term clinical and radiologic follow-up.
Results: All patients (n=15) who responded to steroids were diagnosed as having AIP, whereas all patients (n=7) who did not show a response to steroids were confirmed as having pancreatic cancer. Complete resection was possible in all (6/6; 100%), except one individual who refused surgery.
Conclusion: In the clinical setting of suspected AIP with the continued need of differentiation from pancreatic cancer due to atypical imaging for AIP, "a two-week steroid trial and subsequent assessment of its response" may be helpful in confirming the diagnosis of AIP without negative consequences for resectable pancreatic cancer. However, a steroid trial should be performed carefully by only specialist in pancreatology.