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Colorectal cancer (CRC) has been on the rise among higher income countries -- and that trend is expected to continue for both incidence and mortality rates, a global study found.

More than 1.9 million new CRC cases arose across 185 countries in 2020, with an estimated 930,000 million CRC-related deaths, which accounted for 10.7% of all cancers and 9.5% of cancer-related deaths, reported Eileen Morgan, PhD, of the International Agency for Research on Cancer in Lyon, France, and colleagues in a paper published in .

By 2040, the burden of CRC was projected to increase by 63%, reaching 3.2 million new cases and 1.6 million deaths, with some 80% expected to occur in countries like the United States with a high or very high level of human development index (HDI).

Incidence rates were four times higher in countries with very high HDI in 2020 compared with low HDI countries for both males (35.4 vs 8.2 per 100,000) and females (24.4 vs 6.7 per 100,000).

CRC mortality rates followed a similar pattern, with Eastern Europe showing the highest rates (20.2 per 100,000 males) whereas Southern Asia had the lowest rates (2.5 per 100,000 females).

"Moreover, a close to 3% decline in incidence rates per annum would be needed to keep the future number of cases to present (2020) levels," they noted. And while the largest relative spikes in new CRC cases are expected to occur among transitioning countries (low/medium HDI), absolute increases are predicted to impact high/very high HDI countries the most.

The highest CRC incidence was observed in Australia, New Zealand, and Europe (40.6 per 100,000 males), while the lowest incidence was in Africa and Southern Asian regions (4.4 per 100,000 females).

Across countries, a 10-fold variation was seen in incidence rates among males and females. Both incidence and mortality rates were higher among males.

"Variations in incidence were also observed within regions, for example, Hungary and Slovenia have among the highest rates in males in the Eastern and Southern regions of Europe," the researchers noted, which could reflect the timing of screening.

Reached for comment, Allen Kamrava, MD, of Cedars-Sinai Medical Center in Los Angeles, said "While the precision of these types of studies is low, it is sufficient for what the authors wish to accomplish, which is awareness and education."

"Given that CRC cancers are one of the most common cancers globally," Kamrava added, "raising awareness for proper screening and healthy behavior is a good thing."

CRC ranks third among the most common types of cancer worldwide and comes in second for cancer-related deaths, Morgan's group noted. Moreover, CRC is largely a preventable disease with modifiable risk factors, such as high alcohol or sugar beverage consumption, smoking, and diet (highly processed/junk foods).

Recently, CRC incidence – including more distal tumors and distant-stage disease – has been on the rise among younger individuals below age 50, especially in high-income countries such as the U.S., U.K., and Australia in addition to transitioning countries like Brazil. The American College of Gastroenterology and other organizations have responded by lowering the CRC screening age to 45.

Notably, in Morgan's study, 60.4% of all CRC diagnoses occurred between ages 50 and 74. Nearly 10% were diagnosed before age 50.

The researchers examined Global Cancer Observatory () data from the year 2020 and used it to predict the number of CRC cases and deaths in 2040, which were stratified by age and sex. Predictions were calculated based on global demographic projections for 185 countries using the HDI. Researchers also extracted 2020 population data from the United Nations.

CRC was the most common cancer type in 18 countries, while CRC ranked second or third in 78 more. Six countries reported CRC was the most common cause of cancer-related death, while it came in among the top three leading causes of cancer-related deaths in 104 countries.

The authors acknowledged limitations to the data, specifying that findings and predictions based on extrapolations should be interpreted with caution. GLOBOCAN estimates were taken prior to the pandemic, therefore excluding any potential pandemic-related changes in diagnostic activity. Types of CRC or anatomical subsites were not assessed.

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