ABSTRACT
BACKGROUND: The timing to the first undetectable hepatitis C virus (HCV) RNA level is strongly associated with sustained virologic response in pegylated interferon (Peg-IFN) plus ribavirin combination therapy for patients with chronic hepatitis C (CH-C) with genotype 1. This study was conducted to clarify the impact of drug exposure to Peg-IFN on the timing of HCV RNA negativity in Peg-IFN plus ribavirin combination therapy for CH-C patients with genotype 1. METHODS: A total of 1409 patients treated with Peg-IFN alfa-2b plus ribavirin were enrolled and classified into four categories according to the Peg-IFN dosage. Furthermore, 100 patients were extracted from each Peg-IFN dosage category to adjust for characteristic factors, using the propensity score method. RESULTS: Peg-IFN exposure was dose-dependently associated with the timing of HCV RNA negativity (p ≤ 0.001). The HCV RNA negative rate at week 4 decreased from 12% with a Peg-IFN dose of >1.5 µg/kg/week to 1-3% with a dose of <1.5 µg/kg/week (p ≤ 0.001), and at week 12 the rate had decreased from 44% with a dose of ≥1.2 µg/kg/week to 18% with a dose of <1.2 µg/kg/week (p = 0.001). Treatment failure (patients without a 1-log decrease of HCV RNA at week 4 or a 2-log decrease of HCV RNA at week 12, or positive at week 24) was found in 54-66% of patients given <1.2 µg/kg/week (p ≤ 0.001), and these patients accounted for 64% of the non-responders. CONCLUSIONS: The timing of HCV RNA negativity depends significantly on the Peg-IFN dose. Reducing the Peg-IFN dose can induce a later virologic response or non-response in HCV genotype 1 patients treated with Peg-IFN plus ribavirin.