GI Highlights from the literature
- Guruprasad P Aithal, JournalScan Editor
Allium vegetables to keep gastric cancer at bay…
▶ Zhou Y, Zhuang W, Hu W, et al. Consumption of large amounts of allium vegetables reduces risk for gastric cancer in a meta-analysis. Gastroenterology. Published Online First: 4 April 2011. doi:10.1053/j.gastro.2011.03.057.
Despite a declining incidence, gastric cancer remains the second most common cause of cancer death worldwide. The causative role of Helicobacter pylori in the disease is widely accepted, although, as yet, no country has instituted population screening and treatment as a prevention strategy. Some investigators have reported that the incidence of gastric cancer is lower in regions where the consumption of allium vegetables (onions, leeks, scallions, chives and garlic) is high. This meta-analysis of observational studies has attempted to synthesise all available published evidence examining this issue.
The authors identified 21 studies that included in excess of 500 000 individuals. When the occurrence of gastric cancer was compared between the highest and lowest categories of allium vegetable consumption, the odds of gastric cancer were significantly reduced (OR 0.54; 95% CI 0.43 to 0.65). There was statistically significant heterogeneity between individual study results, but no evidence of publication bias. Summary ORs were similar when subgroup analyses were conducted according to type of study and geographical region. When each allium vegetable was studied individually, there was a significant effect for all types, with the exception of onion leaves, although the effect of the latter was reported in only one study.
Meta-analyses of observational studies, such as this one, cannot control for confounding factors such as age, gender, ethnicity and prevalence of H pylori. In addition, there was heterogeneity between studies in the vast majority of subgroup analyses conducted, suggesting that combining the results of these studies may not be entirely appropriate. The exact constituent of allium vegetables that explains the association between their consumption and reduced occurrence of gastric cancer remains speculative. Finally, it is unclear from the authors' report whether this beneficial effect applies to raw or cooked allium vegetables, or both. Nevertheless, this is an interesting study, and perhaps chemoprevention studies with derivatives of these vegetables will follow in regions at high risk of gastric cancer.
Two or more drinks a day, keeps the GI oncologists in pay…
▶ Schütze M, Boeing H, Pischon T, et al. Alcohol attributable burden of incidence of cancer in eight European countries based on results from prospective cohort study. BMJ 2011;342:d1584.
As gastroenterologists we are so used to dealing with alcohol-related liver cirrhosis that we can forget the burden of alcohol on other conditions. The European Prospective Investigation into Cancer and Nutrition investigators combined prospective cohorts with representative population-based data (>360 000 people; two-thirds women, mainly aged 37–70) on alcohol exposure in eight countries (France, Italy, Spain, the UK, The Netherlands, Greece, Germany and Denmark) to estimate the burden of cancer attributable to current and former alcohol consumption in Europe. Partial alcohol-attributable fractions for consumption higher than the recommended upper limit (two drinks a day for men with ∼24 g alcohol, one for women with ∼12 g alcohol) and the estimated total annual number of cases of alcohol-attributable cancer of causally related cancers were calculated. Figures 1 and 2.
If we assume causality, among men and women, 10% (95% CI 7 to 13%) and 3% (1 to 5%) of the incidence of total cancer was attributable to former and current alcohol consumption. Most of the alcohol-related cancers were gastrointestinal: 44% and 25% for the upper aerodigestive tract, 33% and 18% for the liver, and 17% and 4% for colorectal cancer for men and women, respectively. A substantial part of the alcohol-attributable fraction in 2008 was associated with alcohol consumption higher than the recommended upper limit: 33 000 of 180 000 alcohol-related cancer cases in men and 17 500 of 400 000 alcohol-related cases in women. Hence, in western Europe, an important proportion of cases of cancer can be attributable to alcohol consumption, especially consumption higher than the recommended upper limits. These data support current political efforts to reduce or eliminate alcohol consumption in order to reduce the incidence of cancer, notwithstanding other effects such as those on liver cirrhosis.
Seeing (with the stain) is believing
▶ Di Tommaso L, Destro A, Fabbris V, et al. Diagnostic accuracy of clathrin heavy chain staining in a marker panel for the diagnosis of small hepatocellular carcinoma. Hepatology 2011;53:1549–57.
Cirrhotic liver develops nodularity. In the absence of reliable serological markers, it takes a combination of imaging and expertise to distinguish a potentially dysplastic nodule from a regenerative nodule. It is an even bigger challenge when the nodules are small (≤2 cm), as even with three imaging modalities 20% of nodules which eventually turn out to be liver cancers are misclassified. In contrast, 30% of small nodules are not malignant and accurate diagnosis is critical. The only viable option under the circumstances is to sample these nodules using a very thin (20–21 gauge) needle with the intention to minimise the risk of bleeding and seeding. Considering that optimal management relies upon the histology, certainty of diagnosis is of paramount importance.
Tommaso and colleagues assessed the utility of a combination of a novel panel of immunomarkers (clathrin heavy chain, glypican 3, heat shock protein 70 and glutamine synthetase) in a series of 47 small (≤2 cm) and 39 non-small hepatocellular carcinoma (HCC) cases. The panel specificity was analysed with the adjacent/extranodular cirrhotic liver (n=30) and low-grade (n=15) and high-grade dysplastic nodules (n=16) as a control group. Absolute specificity (100%) for HCC was obtained only when at least two of the markers were positive (which two markers were positive did not matter). The addition of clathrin heavy chain to the panel increased the diagnostic accuracy for small HCCs (from 76.9% to 84.3%), and there was an important gain in sensitivity (from 46.8% to 63.8%). However, in six small HCCs, there was no staining with any of the markers. Cirrhotic control livers were stained for clathrin heavy chain in four cases (13.3%) and for glypican 3 in one case (3.3%).
While the specificity of the marker panel promises its utility even in non-expert hands, the findings need to be confirmed in a larger study in a real-life setting. Further, clinicians should get over the dogma that sampling of potential HCCs should be resisted at all costs.
Alex Ford, Neeraj Bala, Guruprasad Aithal
Gastroenterology, British Medical Journal and Hepatology.
Provenance and peer review Commissioned; internally peer reviewed.