Adequate vs. deep response to UDCA in PBC: To what extent and under what conditions is normal ALP level associated with complication-free survival gain?

Background and aims: Normal alkaline phosphatase (ALP) levels in ursodeoxycholic acid (UDCA)-treated patients with primary biliary cholangitis (PBC) are associated with better long-term outcome. However, second-line therapies are currently recommended only when ALP levels remain above 1.5 times the upper limit of normal (xULN) after 12-month UDCA. We assessed whether, in patients considered good responders to UDCA, normal ALP levels were associated with significant survival gains. Approach and results: We performed a retrospective cohort study of 1,047 patients with PBC who attained an adequate response to UDCA according to Paris-2 criteria. Time to liver-related complications, liver transplantation or death was assessed using adjusted restricted mean survival time analysis. The overall incidence rate of events was 17.0 (95%CI 13.7 - 21.1) per 1,000 out of 4,763.2 patient-years. On the whole population, normal serum ALP values (but not normal GGT, ALT, or AST; or total bilirubin < 0.6 xULN) were associated with an overall absolute complication-free survival gain at 10 years of 7.6 months (95%CI 2.7 - 12.6, p = 0.003). In subgroup analysis, this association was significant in patients with a liver stiffness measurement ≥ 10 kPa and/or age ≤ 62 years, with a 10-year absolute complication-free survival gain of 52.8 months (95%CI 45.7 - 59.9, p < 0.001) when these two conditions were met. Conclusions: PBC patients with an adequate response to UDCA and persistent ALP elevation between 1.1 and 1.5 xULN, particularly those with advanced fibrosis and/or who are sufficiently young, remain at risk of poor outcome. Further therapeutic efforts should be considered for these patients.