Patients with chronic hepatitis C genotype 1 had higher sustained virologic response rates with better treatment duration adherence, while adherence to the assigned dosing interval had less impact in a recent study.
Researchers evaluated treatment adherence among 1,500 adult patients with chronic HCV genotype 1 treated with pegylated interferon-alfa and ribavirin. Adherence to the assigned duration of therapy and the thrice-daily dosing interval for boceprevir (BOC) were determined via patients’ dosing diaries and the amount of study drug dispensed to and returned from participants. The data was collected from the SPRINT-2 (n=1,097, treatment-naive participants) and RESPOND-2 (n=403, participants who failed prior peginterferon/ribavirin therapy) trials.
Sixty-three percent to 71% of patients were 80% adherent or better to treatment duration, and displayed sustained virologic response (SVR) rates between 86% and 90%. Among patients who were less than 80% adherent to duration, SVR rates were lower (8% to 32%; P<.0001). This difference was pronounced among those who had failed previous therapy (8% to 15%).
Between 42% to 52% of patients were 80% adherent or better to the thrice-daily BOC treatment interval. No significant difference in SVR rates was seen among treatment-naive patients (P=.195) according to interval adherence, but SVR rates were lower among nonadherent patients who had failed prior therapy (48% to 50% among those less than 60% adherent vs. 60% to 77%; P=.005).
Investigators said patients with 80% or better duration adherence had similar SVR rates to patients with high adherence to duration and interval (78% to 100% vs. 89% to 91%). Patients who were less adherent to duration had low SVR rates regardless of dosage adherence (0% to 50%).
“The present study shows that the ability to respond successfully to treatment was more dependent on adherence to the actual assigned duration of therapy,” researcher S.C. Gordon, MD, Henry Ford Hospital in Detroit, Mich., told Healio.com. “This ‘duration of viral negativity’ while on therapy translates to higher SVR rates. The study validates previous research, both in HIV therapy and in previous pegylated interferon and ribavirin therapies for hepatitis C, showing that patient adherence is key to a successful treatment course.”