High sensitivity of biliary brush cytology in patients with suspected perihilar or intrahepatic cholangiocarcinoma: a prospective cohort comparison with historical controls

Background: Although biliary brush cytology has a high specificity (95–100 %), the sensitivity is poor (41–67 %). This study aimed to evaluate whether the use of an optimized protocol for brush cytology improves the results in patients with suspected perihilar or intrahepatic cholangiocarcinoma (pCCA/iCCA). Methods: Patients were prospectively included after changing the protocol (June 2021–June 2023) and compared with a historical cohort (January 2017–May 2021). Changes included different brush processing, addition of next-generation sequencing (NGS), and additional sampling (two brush samples and intraductal biopsies). Primary outcome was the sensitivity and the specificity of the procedure. Results: A total of 175 patients were evaluated (62 prospective, 113 historical) of which 165 patients had malignant disease (94 %). After implementation of the protocol, the sensitivity was 88.3 % (95%CI, 76.8–94.8 %) versus 50.5 % (95%CI, 40.6–60.3 %) prior to implementation. Sensitivity of only the first brush sample with the optimized processing did also significantly increase (78 %; 95%CI, 65.5–87.5 %). Specificity was 100 % in both groups (2/2 vs 8/8). Conclusions: A modification in the processing of cytopathology led to a significant improvement in the sensitivity of the first bile duct brush to 78 %. Furthermore, adding NGS increased sensitivity to 83 %, an extra brush sample to 85 %, and intraductal biopsies to 88 %.