THE INCIDENCE OF colon and rectal cancer in adults younger than 50 years increased substantially over a ten year period in several high-income countries, new research has discovered.

The study, published in The Lancet Gastroenterology And Hepatology journal, looked at long-term data for these types of cancer, referred to as colorectal cancers, in 21-population based registries across Ireland, the UK, Australia, Canada, Denmark and Norway.

During the most recent ten-year period up until 2014, the incidents of colon cancer in people aged 0-49 years increased significantly each year in Denmark by 3.1%, in New Zealand by 2.9% and in Australia by 2.9%. The numbers increased in Ireland by 0.8% during that period. 

Significant increases in the incidence of rectal cancer each year were also noted in this age group in Norway (by 4%) in Canada (3.4%), Australia (2.6%), and the UK (1.4%). In Ireland the numbers in this age group fell by 0.3%. 

Increases in the incidence among adults under 50 were most pronounced for rectal cancer, particularly in the 20-29 age group, where rectal cancer incidence increased annually by 18.1% in Denmark and 10.6% in Norway over the past decade.

Colorectal cancer is the third most common cancer worldwide, with an estimated 1·8 million new cases diagnosed and 881 000 deaths associated with the disease in 2018.

“Although the incidence of colorectal cancer in adults younger than 50 years remains much lower compared with that in older age groups, our findings are of concern and highlight the need for action to counteract the rising burden of the disease in younger people,” said lead author of the study, Dr Marzieh Araghi from International Agency for Research on Cancer, Lyon.

“This rise in incidence among younger generations is likely to be driven in part by the changing prevalence of risk factors, such as obesity and poor diet. National programmes to promote healthy diets and physical activity might be the most efficient approach to ensure population-level changes.”

The authors of the study have suggested that the decrease in incidence of colorectal cancer in people over 50 years old in most of the countries studied could be attributed to the introduction of routine screening programmes for premalignant polyps.

In Australia, Canada, and the UK, where age-based screening began in 2006, overall decreases in incidence were more pronounced.

In countries where screening programmes began later, such as in Ireland (2012), Denmark (2014), Norway (2012, pilot programme only), and New Zealand (2017), overall rates have remained roughly stable.