Sustained Virological Response as a Surrogate Marker for Mortality, Decompensated Cirrhosis, or Hepatocellular Carcinoma in People With Chronic Hepatitis C Virus Infection Treated With Direct-Acting Antivirals: Protocol for a Bayesian and Causal Mediation Analysis.

Background: Sustained virological response (SVR) is commonly used as a marker of treatment success in people with chronic hepatitis C virus (HCV) infection. However, there is uncertainty on whether SVR is a validated surrogate marker of successful chronic HCV infection treatment.

Objective: This research project aims to evaluate whether SVR is a good surrogate for all-cause mortality, decompensated cirrhosis, any specific aspect of liver decompensation (jaundice, ascites, hepatic encephalopathy, hepatorenal syndrome, or variceal hemorrhage), or hepatocellular carcinoma in people with chronic HCV infection eligible to receive direct-acting antiviral drugs.

Methods: We will use two ongoing systematic reviews on the effectiveness of direct-acting antiviral drugs in chronic HCV infection as our data sources. The analysis plan is to estimate the regression coefficients or between-studies correlation between SVR and an event using three different Bayesian approaches with OpenBUGS, as outlined in the guidance by the evidence synthesis unit, and estimate the average proportion of the effect mediated through SVR by causal mediation analysis using R.

Results: As of June 19, 2025, the two systematic reviews (one on randomized clinical trials and one on observational studies) on the effectiveness of direct-acting antiviral drugs in chronic HCV infection are ongoing.

Conclusions: We will use the German Institute of Quality and Efficiency in Health Care criterion for surrogacy for cancer, with at least 50% of the treatment effect mediated through SVR, but the information will be reported in a way that allows people to interpret the information using their own criteria.