People infected with both HIV and hepatitis C virus (HCV) who successfully complete 12 months of HCV treatment can experience relapse of their infection, but if they do, it usually happens within the first 12 weeks after therapy is stopped, say the authors of a study published in the November 1 issue of Clinical Infectious Diseases.

The goal of HCV treatment is to maintain an undetectable HCV viral load for at least six months after completing a year’s course of therapy, called a sustained virologic response (SVR). A number of studies have shown that SVRs are less likely for people coinfected with both HIV and HCV, compared with people infected with only HCV. In people infected with HIV and HCV genotypes 1 or 4—the toughest to treat—the likelihood of success is even lower.

What isn’t well characterized, however, are the patterns in HIV- and HCV-coinfected people who relapse after treatment. A relapse is when someone makes it to the end of treatment with an undetectable HCV level, but then has detectable virus again sometime during the next six months.

To describe how often and when relapse occurs, José Medrano, MD, from the Hospital Carlos III in Madrid and his colleagues, examined the medical records of 616 HCV-infected people who received pegylated interferon and ribavirin treatment between 2001 and 2008. Of the 616 people, 386 were coinfected with HIV and HCV.
About 60 percent of those infected with only HCV made it to the end of the year’s worth of treatment with an undetectable HCV viral load, called an end-of-treatment response (ETR). Only 37 percent of coinfected people had an ETR.
Of those who had an ETR, 22 percent of those infected with only HCV experienced an HCV relapse. Conversely, 33 percent of the HIV-positive individuals with an ETR experienced a relapse.

Not surprisingly, relapse was more common in all those infected with HCV genotypes 1 or 4.

HCV treatment relapses occurred almost always within the first 12 weeks after a person completed their HCV treatment regimen, regardless of whether they were coinfected or had only HCV.  In the three patients who experienced HCV viral load rebounds more than 12 weeks after achieving an ETR, researchers suspect that reinfection—not a relapse of previous HCV infection—was to blame in two cases. 
The authors state that better understanding treatment relapse, particularly in people coinfected with HIV and HCV, gives both providers and patients a better sense of what to expect during—and the weeks following—HCV treatment.