The incidence of colorectal cancer (CRC) has increased in young adults in nine high-income countries spanning three continents, according to a study published in Gut. The researchers said this could be due to “changes in early-life exposures that influence large bowel carcinogenesis.”
Researchers assessed long-term data from Cancer Incidence in Five Continents and supplemental sources to report on worldwide CRC incidence rates and trends by age (20 to 49 years versus ≥50 years) through diagnosis year 2012 or beyond in 43 countries across six continents.
Increased CRC among individuals aged <50 years
From 2008 to 2012, age-standardized CRC incidence rates in adults <50 years ranged from 3.5 per 100,000 (95% CI, 3.2-3.9) in India to 12.9 (95% CI, 12.6-13.3) in Korea.
During the most recent decade of available data, CRC incidence in adults <50 years was stable in 14 of 36 countries; declined in Austria, Italy, and Lithuania; and increased in 19 countries, nine of which had stable or declining trends in older adults, including Australia, Canada, Denmark, Germany, New Zealand, Slovenia, Sweden, United Kingdom, and United States.
In Cyprus, Netherlands, and Norway, the increase in CRC incidence among young adults was twice as rapid as the increase observed in older adults. For example, in Norway, the average annual percent change (AAPC) was 1.9 (95% CI, 1.4-2.5) in younger adults and 0.5 (95% CI, 0.3-0.7) in older adults.
Among most high-income countries with available long-term data, the increase in early-onset CRC began in the mid-1990s. The largest increase in young adults with CRC was observed in Korea (AAPC, 4.2; 95% CI, 3.4-5.0) and New Zealand (AAPC, 4.0; 95% CI, 2.1-6.0).