A new study led by American Cancer Society (ACS) researchers shows that early-onset colorectal cancer (CRC) incidence rates are rising in 27 of 50 countries/territories worldwide, 20 of which have either exclusive or faster increases for early-onset disease. In 14 countries, including the United States, rates are increasing in young adults while stabilising in those 50 years and older. The research is published today in the journal The Lancet Oncology.

"The increase in early-onset colorectal cancer is a global phenomenon," said Dr. Hyuna Sung, senior principal scientist, of cancer surveillance research at the American Cancer Society and lead author of the study. "Previous studies have shown this rise in predominately high-income Western countries, but now, it is documented in various economies and regions worldwide."

The primary study objective was to examine contemporary CRC incidence trends in young versus older adults using data through 2017 from 50 countries/territories. Data were compiled using the Cancer Incidence in Five Continents Plus and trends were examined for age-standardised incidence rates of CRC ranging from 1943-2017. Temporal trends were visualised and quantified by age at diagnosis (25-49 years and 50-74 years). Average annual percentage changes (AAPC) were estimated for the last 10 years of data.

During the past decade, incidence rates of early-onset CRC (25-49 years) were stable in 23 countries, but increased in 27 countries, with the greatest annual increases in New Zealand (4.0%), Chile (4.0%) and Puerto Rico (3.8%). Fourteen of the 27 countries/territories showed either stable (Puerto Rico, Argentina, Norway, France, Ireland) or decreasing rates (Israel, Canada, the USA, England, Germany, Scotland, Slovenia, Australia, and New Zealand) in older adults. T

he rise in early-onset CRC was faster among men than women in Chile, Puerto Rico, Argentina, Ecuador, Thailand, Sweden, Israel, and Croatia, while young women experienced faster increases in England, Norway, Australia, Türkiye, Costa Rica, and Scotland. For the remaining 13 countries with increasing trends in both age groups, the annual percentage increase in young compared to older adults was larger in Chile, Japan, Sweden, the Netherlands, Croatia, and Finland, smaller in Thailand, Martinique, Denmark, Costa Rica, and similar in Türkiye, Ecuador, and Belarus. For the last five years, the incidence rate of early-onset CRC was highest in Australia, Puerto Rico, New Zealand, the U.S., and the Republic of Korea (14 to 17 per 100,000) and lowest in Uganda and India (4 per 100,000).

"The global scope of this concerning trend highlights the need for innovative tools to prevent and control cancers linked to dietary habits, physical inactivity, and excess body weight. Ongoing efforts are essential to identify the additional factors behind these trends and to develop effective prevention strategies tailored to younger generations and local resources worldwide," added Sung. "Raising awareness of the trend and the distinct symptoms of early-onset colorectal cancer (e.g., rectal bleeding, abdominal pain, altered bowel habits, and unexplained weight loss) among young people and primary care providers can help reduce delays in diagnosis and decrease mortality."

"This flagship study reveals that increasing rates of early onset bowel cancer, affecting adults aged 25-49, is a global issue. Concerningly, this research has revealed for the first time ever that rates are rising more sharply in England than in many other countries around the world," said Michelle Mitchell, chief executive of Cancer Research UK.

"A cancer diagnosis at any age has a huge impact on patients and their families -- so while it's important to note that rates in younger adults are still very low compared to people over 50, we need to understand what's causing this trend in younger people. More research is needed -- like team PROSPECT, a global Cancer Grand Challenges team who has been awarded £20m to uncover the causes of bowel cancer in younger adults, and strategies to prevent it."