Ángel Lanas
Professor at the Faculty of Medicine of the University of Zaragoza, a researcher at the Aragón Institute for Health Research (IIS Aragón) and CIBERehd, and an honorary professor at the University of Hong Kong (China)
What do you think of the article overall? Is it of good quality?
"The article is complex from a methodological point of view and appears to be rather “stretched” from a statistical point of view, but I didn’t feel it offered anything of substance.
The authors report that 22 per cent of colon cancers may be linked to H. pylori infection, but at no point does this go beyond an association and, of course, the authors do not in any way venture to suggest a causal relationship. There are many other factors that may underlie this association besides the infection itself, such as age, diet, lifestyle, socio-economic status, access to medical tests and many other factors.
The margin of uncertainty reported by the authors is quite high and, when they focus on the highest-quality studies, this association drops to 12 per cent. The heterogeneity between studies is also very high, as the authors themselves point out, and the studies with the greatest bias are those that find the strongest association. Overestimates are made for countries where a great deal of data is missing.
In summary, we would say that the study is interesting, methodologically complex to carry out, and its conclusions must be treated with extreme caution.”
How does this fit in with the existing evidence, and what implications might it have?
“H. pylori infection is indeed clearly linked to gastric cancer. Its link to colorectal cancer is much weaker.
For some time now, mechanistic and epidemiological studies have been carried out in an attempt to link H. pylori infection with colorectal cancer. However, this potential link is, in a sense, counterintuitive.
Colon cancer is a cancer of developed countries, where the prevalence of H. pylori infection is precisely low. Conversely, in developing countries, the prevalence of H. pylori infection and the incidence of gastric cancer are high, whilst that of colon cancer is much lower than in developed countries.
This does not mean that H. pylori cannot play a role in the development of colorectal cancer, but this first needs to be demonstrated and, if it does, its effect is limited.
In my view, the study has no practical implications for current strategies for the prevention of colorectal cancer or the eradication of H. pylori.”