Systematic review: the association between obesity and hepatocellular carcinoma - epidemiological evidence

Evidence increasingly implicates obesity as an independent risk factor for different cancers. We examined such evidence for hepatocellular carcinoma.

To review the effect of increased levels of body mass index on hepatocellular carcinoma risk.

We reviewed systematically the literature examining the association between increased body mass index and hepatocellular carcinoma risk. For each identified study, relevant data were extracted and appraised.

Ten cohort studies (>90 million person-years), one nested case-control study (244 cases) and two case-control studies (494 cases) were identified. Of the cohort studies, 75% of person-years related to North Americans, 15% to East Asians, and 10% to Europeans. Three cohort studies adjusted for alcohol consumption, only one cohort study adjusted for hepatitis infection status. Seven cohort studies found a positive association between obesity (body mass index > or =30 kg/m(2)) and hepatocellular carcinoma risk (relative risks ranging from 1.4 to 4.1); two reported no association; and one reported a significant inverse association for a population subgroup (relative risk = 0.7, 95% confidence interval: 0.5-0.9).

Although most studies did not adjust for confounders and most data relate to a single world region, the overall evidence is suggestive of an increased hepatocellular carcinoma risk in obese and overweight individuals.