Helicobacter pylori is firmly established as a cause of gastric cancer, but its relationship to cancer further down the digestive tract has remained contested. An international study led from the LKS Faculty of Medicine at HKU with the University of California San Diego, and involving Erasmus MC and Brown University, pooled 43 international studies covering about 48.7 million participants and combined the result with global incidence data for 2022.
Exposure to the bacterium was associated with a 1.59-fold higher risk of colorectal cancer compared with no exposure, which the authors translate into roughly 22 per cent of global colorectal cancer cases potentially attributable to it. Restricting the analysis to the fourteen population-based and cohort studies, the more methodologically conservative subset, brings that figure down to about 12 per cent, and the paper is explicit that the findings are associational.
The geography and the birth-cohort pattern are both striking. The Western Pacific region showed the highest estimated proportion at about 25 per cent, with China accounting for the largest absolute number of potentially linked cases. The estimated proportion rose from 9.5 per cent among people born before 1947 to 15 per cent among those born between 1963 and 1977, a gradient that intersects with the much-discussed rise in early-onset colorectal cancer. The study appeared in eGastroenterology.
Colorectal cancer caused nearly 900,000 deaths in 2022, so even a modest attributable fraction represents a large number of preventable cases. The authors stress that prospective and interventional studies are still required before eradication could be recommended as colorectal cancer prevention. The question of whether treating one infection could shift the incidence of a second cancer is now, however, squarely on the research agenda.