This study compares the safety profiles of pegylated interferon (PEG-IFN) α-2a and α-2b administered in combination with ribavirin, based on the variable of time to withdrawal from treatment due to adverse events. We conducted a real-world retrospective cohort study using the Japanese interferon database. Based on eligibility criteria, individuals with chronic hepatitis C virus (HCV) infection were identified in the database covering the period December 2009 to August 2015. The primary outcome measure was defined as difference in time to withdrawal from treatment due to adverse events between patients receiving PEG-IFN α-2a combined with ribavirin and those receiving PEG-IFN α-2b combined with ribavirin. The difference was analyzed using the multivariate Cox proportional hazards regression model. A frailty model was also applied to consider regional (prefectural) variation. After eligibility evaluation, 11058 individuals were included in the analysis. 3774 were treated with PEG-IFN α-2a, and 6764 with PEG-IFN α-2b, with 11.84 and 12.30% respectively withdrawing from treatment due to adverse events. The Cox model showed no significant difference between the two groups (hazard ratio (HR), 95%CI; 0.918, 0.817 to 1.031; p=0.1475). The results were consistent even when regional variation and other confounding variables were adjusted in the frailty model. In conclusion, there may be no difference in time to withdrawal from treatment due to adverse events between PEG-IFN α-2a and PEG-IFN α-2b combined with ribavirin. Applying the method used here to future studies using novel treatment regimens may also provide important information for the treatment of chronic HCV infection in clinical practice.
2016 The Pharmaceutical Society of Japan