Trial effect refers to the impact of clinical trial participation on treatment outcomes. Little literature exists evaluating the magnitude and direction of trial effect in hepatitis C virus (HCV).
A single-center, retrospective study on HCV antiviral therapy recipients was conducted. Sustained virologic response (SVR), virologic response at treatment weeks 4 and 12, dose interruptions, and adverse events were compared between clinical trial participants and standard-of-care antiviral recipients between September 2000 and November 2011.
A total of 449 patients were evaluated (trial: 89, nontrial: 360). Patients were matched for age (trial: 47 years, nontrial: 45 years), sex (male: trial, 74%; nontrial, 72%), and ethnicity (white: trial, 87%; nontrial, 78%). The groups differed in the incidence of genotype 1 infection (trial: 83%, nontrial 53%; P<0.001), liver biopsy rates (trial: 98%, nontrial: 66%; P<0.001), and history of psychiatric illness (trial: 30%, nontrial: 53%; P<0.001). On intent-to-treat analysis, SVR rates were found to be similar (trial: 51%, nontrial: 54%; P=0.86), even when stratified for genotype (G1: trial, 47%; nontrial, 47%; P=0.78). Interferon dose reductions (trial: 18%, nontrial: 6%; P<0.01) were more likely in trial patients, whereas treatment discontinuation because of side effects (trial: 8%, nontrial: 18%; P<0.02) was less likely in them. No differences in safety issues were identified.
Overall, a trial effect resulting in improved or diminished SVR rates was not identified. Other potential positive and negative variables should be focused upon for HCV patients deliberating between clinical trial participation and receiving standard-of-care treatment.