Longitudinal analysis of CA19-9 reveals individualised normal range and early changes before development of biliary tract cancer in patients with primary sclerosing cholangitis.

Background Primary sclerosing cholangitis is associated with an increased risk of biliary tract cancer. Carbohydrate antigen 19-9 (CA19-9) can be used to screen for these malignancies. Aim To perform a longitudinal analysis of CA19-9 in patients with primary sclerosing cholangitis. Methods We conducted a retrospective analysis of CA19-9 values in patients who had primary sclerosing cholangitis, with and without biliary malignancy. We calculated the index of individuality and reference change value in patients who were cancer-free. Long-term analysis of CA19-9 in cancer-free patients was performed and we assessed the change of CA19-9 prior to diagnosis of cancer. Results We obtained 1818 CA19-9 values from 247 patients, including 32 with malignancy. Median CA19-9 in cancer-free individuals was 15.6 U/mL. The index of individuality was 0.37 and the reference change value was 46.23%. In cancer-free patients, no significant change in CA19-9 was observed at 1, 2, 5, 7, 10, 15, and 20 years after initial diagnosis of primary sclerosing cholangitis. In patients with biliary tract cancer, CA19-9 was higher at 3 months prior to diagnosis (P < 0.05) than at 6 months before diagnosis and was also higher than at 3 months prior to last follow-up in cancer-free patients (P < 0.05). In 92.9% of patients with biliary cancer, we found an increase in CA19-9 of >46.23% in the year prior to cancer diagnosis. Conclusions CA19-9 in patients with primary sclerosing cholangitis is highly individual, and the reference change value should be preferred to reference intervals. In this study, CA19-9 remained stable in patients who were cancer-free but increased early in those who developed biliary tract cancer. Regular CA19-9 measurement might improve early detection of these malignancies.