Abstract
OBJECTIVES:
Combination therapy with pegylated interferon (Peg) and ribavirin (RBV) is the standard of care for the treatment of chronic hepatitis C virus (HCV) infection. This analysis compares the cost efficacy of treatment with pegylated interferon alfa-2b plus ribavirin (Peg-2b plus RBV) with pegylated interferon alfa-2a plus ribavirin (Peg-2a plus RBV) in hypothetical cohorts of 100 chronic HCV patients comprised 75% of genotype 1.
METHODS:
A decision analysis model was constructed from the viewpoint of a managed care organization to compare Peg-2b plus RBV (1.5 mcg per kilogram per week plus RBV 800 mg per day) and Peg-2a plus RBV (180 mcg per week plus RBV 1,000-1,200 mg per day) pursuant to the label dosing approved by the U.S. Food and Drug Administration. The model also included the so-called weight-based dosing regimen with Peg-2b plus RBV (1.5 mcg per kilogram per week plus RBV 10.6 mg/kg per day). Patient weight was assumed to be 80 kg. For purposes of this analysis, early virologic response (EVR), defined as viral negative or 2-log drop in viral load, was assessed at 12 weeks for only genotype 1 patients, and nonresponders were assumed to discontinue therapy. The positive predictive value (PPV) was calculated for each treatment group for genotype 1 patients, which is determined from the values for EVR and sustained viral response (SVR). Genotype 2 and genotype 3 patients were assumed to be treated for 24 weeks. Treatment duration and efficacy data were obtained from the published literature. Product pricing was based on average wholesale price, October 2004, and sensitivity analysis was performed using prices from the Federal Supply Schedule. Economic outcomes were determined from hypothetical 100-patient cohorts assumed to be comprised 75% of genotype 1 HCV.
RESULTS:
Taking into account both EVR and SVR, the PPV for genotype 1 patients was 0.63 and 0.57 for Peg-2b plus RBV and Peg-2a plus RBV, respectively. The proportion of treated patients achieving SVR would be nearly identical, (53.6%) and (53.8%) for Peg-2a plus RBV and Peg-2b plus flat RBV, respectively. For Peg-2b plus weight-based RBV, the proportion of patients achieving SVR was higher (61.4%). Consequently, this leads to fewer overall treatment weeks for the Peg- 2b plus RBV cohorts. Therefore, the cost per successful treatment (defined as SVR) was 19.4% less ($37,638) for Peg-2b plus flat dosing of RBV as compared with Peg-2a plus RBV ($46,717). When Peg-2b plus RBV was dosed 1.5 mcg per kilogram per week plus RBV 10.6 mg/kg/day, then the cost per SVR was $39,045. The cost for the 100-patient cohort was $2,024,846 for Peg-2b plus RBV, $2,397, 529 for Peg-2b plus weight-based RBV, and $2,505,317 for Peg-2a plus RBV. This difference is due to a lower PPV in the Peg-2a plus RBV groups and hence more patients treated in spite of a low probability of achieving SVR.
CONCLUSIONS:
The results of this cost-efficacy analysis suggest that treating HCV genotype 1 patients with Peg-2b plus RBV may result in savings to a health care system because fewer of these patients are treated beyond 12 weeks when achieving sustained viral clearance is unlikely.