Reacción a "The increase in colorectal cancer in young adults could be due to a bacterial infection in childhood"

The paper shows that mutational signatures in colorectal cancer vary between countries, which is good evidence of regional differences in environmental exposures. However, the observation that colibactin signatures are commoner in young colorectal cancers is not good evidence that increasing colibactin exposure is an important cause of the recent increase in colorectal cancer in successive generations born since the 1950s. An equally plausible explanation of these data is that the incidence of colorectal cancers (CRCs) caused by early exposure to colibactin (like CRCs caused by inherited APC mutations) rises less steeply with age than for the majority of CRCs. Their hypothesis should be tested by similar studies on stored histology samples from CRCs diagnosed in successive periods. That would show whether there has been a secular increase in the proportion of CRCs with these signatures.