A Cochrane review included 18 RCTs with a total of 10,499 participants. The results from 17 of 18 of these RCTs, published between 1995 and 2011, were suitable for meta-analysis and allowed us to quantifying the therapeutic efficacy of interferon in terms of disease-free survival (17 trials) and overall survival (15 trials). Adjuvant interferon was associated with significantly improved disease-free survival (HR (hazard ratio) = 0.83; 95% CI 0.78 to 0.87, P < 0.00001) and overall survival (HR = 0.91; 95% CI 0.85 to 0.97; P value = 0.003). Adverse events included fever and fatigue, but toxicity disappeared after treatment discontinuation.