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.To perform a longitudinal analysis of CA19-9 in patients with primary sclerosing cholangitis.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.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.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.
