Increase of early-onset colorectal cancer: a cohort effect

Scientists from the International Agency for Research on Cancer (IARC) reveal the existence of significant age–period–cohort effects in the incidence of early-onset colorectal cancer in Australia, Canada, the United Kingdom, and the USA, in a new brief communication published in the Journal of the National Cancer Institute. The findings imply increasing trends being driven by novel unknown exposures that occur in childhood or very early adulthood and that may accumulate throughout the lifespan. Early-onset colorectal cancer is colorectal cancer that develops before the age of 50 years.

This is the first study to apply a formal age–period–cohort model to examine colorectal cancer trends in these countries. The research team assessed trends by country and by sex. They found that the increase started among cohorts born in about 1955–1960 in all four countries. The rate of increase in recent years was about 4–5% per year (6% per year in England) and was even higher among very young adults. The study showed that the increase is similar in both men and women.

The research team estimates that if these trends continue, the incidence of early-onset colorectal cancer will double approximately every 15 years in all four countries and in both sexes. These results have strong implications for managing and understanding this increase in the incidence of early-onset colorectal cancer, and also for the strategy to search for the underlying cause or causes driving these increases.

Downham L, Laversanne M, Perdomo S, Filho AM, Bray F, Brennan P
Increase of early-onset colorectal cancer: a cohort effect
J Natl Cancer Inst. Published online 23 August 2025;
https://doi.org/10.1093/jnci/djaf238

Read the article