Combination therapy (interferon alfa and ribavirin) in the treatment of chronic hepatitis C: a rapid and systematic review.

BACKGROUND: Hepatitis C is a viral disease of the liver, which frequently causes few or no symptoms at first infection but has a high probability of becoming an insidious chronic disease. Treatment has traditionally been with interferon alfa but only a small proportion of patients have been cured by this method. The recent introduction of ribavirin, given in combination, has led to a re-appraisal of the management of chronic hepatitis C. The current report considers the additional benefit of combination therapy (interferon alfa and ribavirin) compared with monotherapy (interferon alfa alone) for the treatment of patients with chronic hepatitis C. It supersedes two reports of combination therapy conducted by the Scottish Health Purchasing Information Centre and the Wessex Institute for Health Research and Development. OBJECTIVE: To review the clinical effectiveness and cost-effectiveness of combination therapy with interferon alfa and ribavirin in patients with chronic hepatitis C. METHODS - EFFECTIVENESS: Electronic databases were searched from 1993 to the end of 1999, to identify randomised controlled trials (RCTs) or systematic reviews of RCTs that evaluated interferon alfa in combination with ribavirin compared with interferon alfa alone (or placebo) in patients with chronic hepatitis C. Bibliographies from previous studies were also examined. METHODS - ECONOMIC ANALYSIS: The economic evaluation is based on the three largest RCTs of combination therapy, and a pooled analysis of two of these trials. Sustained virological response rates were entered into a spreadsheet model incorporating a hypothetical cohort of 1000 patients who were followed over a 30-year period. RESULTS - EFFECTIVENESS: Nineteen RCTs and two meta-analyses were identified. The methodological quality of the included studies was variable, though the larger RCTs and meta-analyses were considered to be of high quality. Results of these trials indicate that combination therapy produces larger sustained response rates than monotherapy. For patients naive to interferon treatment, sustained virological response rates were: 33% (95% confidence interval (CI), 29 to 37) for combination therapy compared with 6% (95% CI, 3 to 10) for monotherapy, based on 24 weeks of treatment; and 41% (95% CI, 36 to 45) compared with 16% (95% CI, 13 to 19), respectively, for 48 weeks of treatment. For patients who had relapsed following a previous course of interferon, sustained virological response rates were 49% (95% CI, 42 to 57) compared with 5% (95% CI, 2 to 9), respectively, based on 24 weeks of treatment. Two groups of chronic hepatitis C patients are expected to benefit from combination therapy: interferon-naive patients and relapse patients. RESULTS - ECONOMIC ANALYSIS: A 4-week cycle of interferon alfa at 3 mU three times a week costs pound 194; ribavirin costs pound 543. Thus, ribavirin substantially increases drug costs compared with interferon monotherapy. Six months of combination therapy will cost pound 4422 (excluding monitoring costs). For interferon alfa-naive patients, the additional discounted cost per quality-adjusted life-year (QALY) gained from treatment with combination therapy for 6 months compared with no active treatment is pound 7578. For patients who have relapsed after a previous course of interferon alfa, the additional discounted cost per QALY gained from treatment with combination therapy for 6 months compared with monotherapy for 6 months is pound 3503. A subgroup analysis was conducted to examine the sensitivity of the cost per QALY based on the response rates of different patient subgroups (chronic hepatitis C patients with between none and five favourable response factors). This shows it is worth treating all patients with combination therapy as first-line treatment for 6 months, but only worth treating those with one or two response factors for a further 6 months. Those with three or four factors do well by 6 months, but gain very little from furt