Background: Patients with chronic hepatitis C (CHC) and concomitant type 2 diabetes mellitus (DM) show a higher risk of developing hepatocellular carcinoma (HCC). Successful antiviral therapy has reduced the incidence of post-therapy HCC, but the presence of DM still represents an unfavourable predictive factor even in cured patients. Metformin (MET) is recommended as a first-line therapy for DM, and its use is associated with a significant reduction in HCC among diabetic patients with chronic liver disease of different etiology, but very few studies specifically address this issue in patients with CHC.
Aim: the aim of this review is to evaluate whether the use of MET induces a significant decrease in HCC in diabetic patients with CHC, treated or untreated with antiviral therapy.
Methods: A search of PubMed, Medline, Web of Sciences and Embase was conducted for publications evaluating the role of MET in reducing the risk of HCC in patients with DM and CHC, with no language and study type restrictions up to 30 June 2023. Only studies fulfilling the following inclusion criteria were considered: (1) data on the incidence of HCC in the follow-up of diabetic patients with CHC only; (2) follow-up ≥24 months; (3) sufficient data to establish the rate of diabetic patients with CHC treated with metformin or other antidiabetic medications; and (4) data on the type of antiviral treatment and the clinical outcome.
Results: Three studies met the inclusion criteria. A prospective cohort study considering only patients with DM and untreated advanced CHC, or non-responders to interferon (IFN) therapy, showed that the use of MET was associated with a significant decrease in HCC incidence, liver-related death and liver transplants. A recent retrospective study focusing on a large-scale nationwide cohort of patients with CHC in Taiwan successfully treated with IFN-based therapy stratified patients into 3 groups: non-MET users, MET users and non-diabetic patients, with 5-year cumulative rates of HCC of 10.9%, 2.6% and 3.0%, respectively, showing a significantly higher HCC risk in non-MET users compared with MET users and with non-diabetic patients, while it was not significantly different between MET users and non-diabetic patients. In a recent Italian cohort study focusing on 7007 patients with CHC treated and cured with direct-acting antiviral agents (DAAs), a combined effect of DM and MET therapy was found, showing a higher incidence of HCC in diabetic patients not taking MET compared with those without DM and those with DM taking MET.
Conclusion: according to the current evidence, the use of MET should be encouraged in diabetic patients with CHC in order to reduce the risk of HCC; however, a well-designed randomized controlled trial is needed to establish the generalizability of the beneficial effects of MET in this particular subset of patients.
Keywords: antidiabetic therapy; chronic hepatitis C; cirrhosis; diabetes mellitus; direct-acting antiviral agents; hepatitis C virus; hepatocellular carcinoma; interferon; metformin.