Worrying increase in colorectal cancer rates among people under 50 worldwide

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The number of people under the age of 50 diagnosed with colorectal cancer is increasing worryingly globally, according to a recent survey. While previous studies indicated an increase in high-income countries, this trend would now also be observed across different types of economies, including developing countries. This increase is probably due to the increase in unhealthy eating habits and metabolic diseases.

Affecting nearly 2 million people per year worldwide, colorectal cancer is the third most diagnosed form of cancer and the second leading cause of cancer death. The 5-year survival rate is around 90% if diagnosed early, but does not exceed 10% if diagnosed late. While the disease was initially thought to primarily affect older adults, studies have reported increasing incidence rates among younger adults (under 50), particularly in high-income countries, such as Australia, Canada, New Zealand, the United Kingdom and the United States.

On the other hand, trends are generally decreasing or stable among those over 50, probably due to the reduction of risk factors (stopping smoking and alcohol, improving diet, etc.) and efforts raising awareness of early detection. An increase in the rate of colorectal cancer among young adults (or early-onset colorectal cancer) has also been observed in South Korea and Hong Kong, but in parallel with that among older adults.

However, the survey co-led by the American Cancer Society indicates that the rise in early-onset colorectal cancer is a global phenomenon and not limited to high-income countries. “
The increase in early-onset colorectal cancers is a global phenomenon “, Hyuna Sung, senior scientist in charge of cancer surveillance research at the American Cancer Society and lead author of the study, told the Guardian. “ Previous studies have shown this increase primarily in high-income Western countries, but it is now documented in various economies and regions around the world. ».

An increase in 27 out of 50 countries

As part of their investigation, Sung and colleagues compared trends in colorectal cancer incidence among young adults to those among older adults, using data from 50 different countries and territories between 2007 and 2017. on disease incidence come from the Cancer Incidence in Five Continents Plus database of the WHO International Agency for Research on Cancer. Human development index data (the rate of development of countries based on the quality of life of citizens) comes from the United Nations Development Program (UNDP).

According to the results, published in the journal Lancet
Oncology
colorectal cancer rates among adults aged 25 to 49 increased in 27 of the 50 countries studied. The largest annual increases are seen in New Zealand (4%), Chile (4%), Puerto Rico (3.8%) and England (3.6%), indicating the diversity of countries. The incidence appears to be increasing more rapidly among women than men in England, Norway, Australia, Turkey, Costa Rica and Scotland.

Trends in colorectal cancer incidence rates among young adults (25 to 49 years) and older adults (50 to 74 years). © Hyuna Sung et al.

An increase due to poor eating habits

Although the potential causes are not yet clear, researchers believe the rise is due to increases in poor eating habits, physical inactivity and metabolic diseases, such as obesity, among young adults. This growing trend among those under 50 could also lead to an increase in prevalence among older adults over the coming decades.

« The global scale of this worrying trend highlights the need for innovative tools to prevent and control cancers linked to dietary habits, physical inactivity and excess weight. “, says Sung. “ Continued efforts are essential to identify additional factors driving these trends and to develop effective prevention strategies tailored to younger generations and local resources worldwide », she adds.

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However, the study has certain limitations. Data on early-onset colorectal cancer rates are limited to 2017 and may not reflect current trends. They also come from subnational registers and may not represent the entire population of each country. On the other hand, the rate of increase in England is surprisingly higher than in other UK countries (1.55% for Wales, 0.64% for Scotland and 0. 54% for Northern Ireland), raising questions about the reliability of the data.

« Comparing international data on cancer rates is a difficult task, because the quality and availability of data varies widely, we must resist the urge to jump to conclusions, especially when the data is conflicting and complicated », Estimates David Robert Grimes, assistant professor of biostatistics at Trinity College Dublin, who was not involved in the study.

Furthermore, although the rates seem to be increasing among young adults, they still remain low compared to those over 50. In the United Kingdom, for example, colorectal cancer represents only one in 20 cancers diagnosed in people under 50. Nevertheless, the study researchers believe that more awareness and information campaigns are needed among both young people and health care providers, in order to reduce mortality risks.

Source : The Lancet Oncology
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