There is considerable variability in the virologic response of patients with chronic hepatitis C to antiviral therapy. Recently, the NIH Con-sensus Development Panel affirmed that a sustained virologic response (SVR) is the optimal outcome of therapy. SVR is defined as undetectable HCV RNA in serum at the end of therapy and for at least 6 months thereafter.
Preliminary studies have shown that once patients achieve an SVR, almost all are 'cured' of their HCV infection as late relapse occurs in fewer than 2 or 3% of patients. SVR is associated with significant improvement on liver biopsy. There is some evidence that SVR also appears to decrease the subsequent risk of HCC.
Other possible responses include loss of detectable HCV RNA from serum during therapy followed by its reappearance when treatment is stopped (relapse). The term non-responder is used for those patients in whom HCV RNA may or may not decrease but does not become undetectable during therapy. An uncommon pattern is 'breakthrough' where HCV RNA becomes undetectable on therapy but then reappears even while the patient is still receiving treatment.
In addition to these virologic patterns of response, improve-ments (reductions) in serum aminotransferases may occur (referred to as a biochemical response) and a decrease in necro-inflammatory activity may be noted on liver biopsy (histologic response). Assessment of antiviral therapy has focused on SVR.