Globally, diagnoses and deaths from colorectal cancer (CRC) more than doubled over the past 30 years, according to a new analysis of 204 countries.
However, trends in CRC incidence and deaths varied by age, region, and sex. Investigators expressed particular concern over the rising incidence rates among people younger than 50 and those living in low and middle sociodemographic index countries in Asia and Africa.
“These results provide comprehensive and comparable estimates that can inform efforts for equitable colorectal cancer control worldwide,” the authors write. However, “further research is required to understand the causes of the colorectal cancer burden in younger adults (aged <50 years) and the main risk factors, including obesity, physical inactivity, alcohol consumption, smoking, and an altered gut microbiome, that might have led to the rise in the colorectal cancer burden.”
The study was published online April 7 in The Lancet Gastroenterology and Hepatology.
CRC is the third leading cause of cancer deaths worldwide, but data on incidence and mortality by location, age, and sex remain less clear.
In the current Global Burden of Diseases, Injuries and Risk Factors Study, researchers evaluated age, sex, and geography-level estimates of CRC incidence, deaths, and disability-adjusted life-years (DALYs) from 204 countries between 1990 and 2019.
The authors found that cases of CRC increased by almost 2.6-fold over the 30-year study period, from 842,098 to 2.17 million. Deaths from CRC increased at a similar but slightly lower rate — rising 2.1-fold over the same period, from 518,126 to 1.09 million. DALYs also nearly doubled, going from 12.4 million in 1990 to 24.3 million in 2019.
In addition, the global age-standardized incidence rate increased from 22.2 to 26.7 per 100,000.
Overall, the age-standardized mortality rate decreased slightly, from 14.3 to 13.7 per 100,000; however, only high-middle and high sociodemographic index regions experienced a decrease; low and middle sociodemographic index regions experienced an increase. The age-standardized DALY rate also declined overall, from 308.5 per 100,000 in 1900 to 295.5 per 100,000 in 2019.
The authors further broke down CRC incidence and deaths by age, region, and sex.
Over the study period, males demonstrated greater increases in CRC incidence, deaths, and DALYs compared to females. In 2019, the age-standardized CRC incidence rate was 1.5 times higher in males (33.1 vs 21.2 per 100,000), as was the age-standardized mortality rate (16.6 vs 11.2 per 100,000). The age-standardized DALY rate showed a similar trend by sex — 360 vs 238 per 100,000 in males vs females.
Trends varied by age as well. CRC incidence rates increased the most in people aged 85 and older, followed by those between 20 and 49 years, while rates decreased for those between 50 and 80 years in high sociodemographic index countries.
Geography mattered too. China, the US, and Japan demonstrated the highest number of new CRC cases across all ages and for both sexes in 2019 — 607,900 in China, 227,242 in the US, and 160,211 in Japan.
In terms of mortality, China, the US, and India had the highest CRC death counts: 261,777 in China, 84,026 in the US, and 79,098 in India.
When it comes to age-standardized incidence rates, Taiwan, Monaco, and Andorra were at the top: Taiwan with 62 per 100,000 cases, Monaco with 60.7 per 100,000, and Andorra with 56.6 per 100,000.
On the other hand, Somalia, Niger, and Bangladesh had the lowest age-standardized incidence rates, 5 per 100,000 in Somalia and 5.6 per 100,000 in Niger and Bangladesh.
The highest age-standardized mortality rates occurred in Greenland, Brunei, and Hungary: 31.4 per 100,000 in Greenland, 30.3 per 100,000 in Brunei, and 28.6 per 100,000 in Hungary.
The relative contribution of different risk factors also varied by region. For example, in sub-Saharan Africa and lower-income countries in Asian, diets low in calcium and milk were the main CRC risk factors. In contrast, smoking and alcohol consumption were the main risk factors driving CRC in high-income regions.
Still, the reasons underlying some of these trends — such as the increasing incidence of CRC in patients under the age of 50 — remain uncertain. One possible explanation for this trend, the researchers point out, is the birth cohort effect, which suggests that those born in the second half of the 20th century are increasingly exposed to potentially modifiable risk factors, such as an unhealthy diet, obesity, and sedentary lifestyles.
Overall, the authors note that the data generated in this study provide an important resource for both patients and oncologists about current trends in incidence and mortality and where gaps in preventive measures may exist.
In particular, the authors conclude that “public health interventions for colorectal cancer awareness, screening and prevention through containment of modifiable risk factors such as alcohol, smoking and unhealthy diet…and obesity are key to stemming the tide of colorectal cancer worldwide.”
The study was funded by the Bill & Melinda Gates Foundation. The authors have disclosed no relevant financial relationships.
Lancet Gastroenterol Hepatol. Published online April 7, 2022. Abstract