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

P>Background Evidence increasingly implicates obesity as an independent risk factor for different cancers. We examined such evidence for hepatocellular carcinoma. Aim To review the effect of increased levels of body mass index on hepatocellular carcinoma risk. Methods 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. Results 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 >= 30 kg/m2) 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). Conclusion 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.