Abstract| Volume 24, SUPPLEMENT 1, S300, 2022

Tumor Origin and Diagnostic Accuracy in Patients with Pancreatic and Periampullary Cancer: A Nationwide Study

      Introduction: The aim of the present study was to investigate the relative frequency of diagnosed periampullary cancers (pancreatic cancer (PC), distal cholangiocarcinoma (dCCA), ampullary cancer (AC) and duodenal cancer (DC)) for both patients with curative and palliative intention and to evaluate diagnostic accuracy, including in terms of trends and regional differences, as well as survival.
      Method: Data from patients diagnosed with periampullary cancer from 2010-2019 was retrieved from the Swedish National Registry for Pancreatic and Periampullary Cancer. The accuracy of preoperative diagnosis compared with the postoperative histopathological diagnosis was assessed. Postoperative survival of individual periampullary cancers was estimated using Kaplan-Meier method.
      Results: In patients with palliative treatment intention 84% were diagnosed with PC, 4.4% dCCA, 5.1% AC and 6.9% DC. In patients treated with pancreatoduodenectomy for periampullary carcinoma the histopathological diagnosis was PC in 63%, dCCA in 13%, AC 17% and DC 7.2%. Fifteen percent of PC patients were preoperatively misdiagnosed as other periampullary tumors, and 23% of non-pancreatic periampullary cancers were misdiagnosed as a PC. DCCA had the lowest overall diagnostic accuracy, 162/356 (46%). Regional differences in frequency of tumor origins were found, for PC 48-71% and dCCA 9.2-24%. DC and AC had significantly better survival compared to dCCA and PC (p<0.001). PC showed worse survival than dCCA (p<0.001),see figure.
      Conclusions: The proportion of non-pancreatic periampullary cancer is substantially higher in patients with histopathological verification compared to clinical diagnosis. The rate of misdiagnosis for periampullary carcinoma needs to be taken into account in patients where e.g. neoadjuvant oncological treatment is considered.