Historically, treatment for chronic hepatitis C virus (HCV) infection consisted of weekly injections of interferon accompanied by daily oral doses of the broad-spectrum antiviral drug ribavirin. Both drugs would need to be taken for 48 weeks. At best, the side effects from this therapy were highly unpleasant and the combination was not highly effective.
Today in Canada and other high-income countries, more effective and safer interferon-free regimens called direct acting antivirals (DAAs) are available. Over the next year more combinations of potent DAAs will become licensed.
Reviewing the Impact of Interferon
Researchers at the University of Toronto conducted an intensive review (called a systematic review and meta-analysis) of 37 published studies in which interferon was used as treatment for HCV infection. These studies included data from 22,858 participants. The overall rate of cure (also known as a sustained virological response, or SVR) was 48%. Among participants who were cured, 3% subsequently developed liver cancer. Among participants who were not cured, rates for the subsequent development of liver cancer were 12%.
Most of the studies reviewed were retrospective in design. That is, such studies reviewed data that had already been collected for one purpose in the past and re-analysed the data for another purpose. Only some of the studies reviewed collected data on factors such as the presence of type 2 diabetes and alcohol intake. Therefore, the effect of these factors on the subsequent risk of liver cancer could not be assessed by the Toronto team. However, data from large numbers of patients were assessed as part of the review and this provides a very good idea of the risk of liver cancer among people who were treated with interferon.
According to the Toronto team, the risk for subsequently developing liver cancer among participants who received interferon therapy and who were cured decreased by 76%.
The analysis by the Toronto researchers is timely and helpful. It can be used as a reference with which to compare liver cancer rates among people who use modern-day DAAs.
Hosni A, Hansen T, Sampalis J, et al. The development of hepatocellular carcinoma in patients who have obtained a sustained virologic response (SVR) vs. no SVR after antiviral therapy for hepatitis C: a systematic review and meta-analysis. American Society of Clinical Oncology Annual Meeting, Chicago, 3-7 June 2016. Abstract 1551.