Global Cancer Trends – age matters, sometimes!
Review by Prof. Eamonn Quigley (USA)
Study Summary
A knowledge, in as much depth as possible, of trends in cancer incidence is vital to those who oversee heath care delivery, prioritize areas for research, and seek to develop new therapies. In addition, comparing trends in various parts of the world and examining relationships with dietary patterns and socioeconomic factors can provide valuable hints to carcinogenesis or, at the very least, might reveal contributory phenomena. Along with this, there has been an increasing concern that the rates of certain cancers are increasing disproportionately among younger adults. This study, based on the database curated by the International Agency for Research on Cancer (IARC), compared trends in 13 cancer types between younger (aged 20-49) and older (aged ≥ 50) adults in 42 countries around the world between 2003 and 2017. When average annual percentage change in cancer (AAPC) incidence rates was examined for these cancers, rates for thyroid, breast, kidney, and endometrial cancers and leukemia increased in most countries in both younger and older adults. The largest AAPC occurred for thyroid cancer at 3.57% and 3% for younger and older adults respectively; here, rates varied significantly between countries ranging from an increase of over 15% in China to a slight decline in the Philippines and Uganda. For colorectal cancer, in contrast, while an increased incidence (AAPC = 1.45%) was seen in most countries among younger adults, this trend was evident in only 50% of countries in older adults (AAPC = 0.37%) with declines evident for older adults in New Zealand, Australia, Canada, the United States, Switzerland, Germany, Austria and Czechia, and Israel. However, many of these same countries witnessed an actual increase in colorectal cancer incidence in younger adults. Rates for pancreatic cancer increased similarly in younger (AAPC = 1%) and older (AAPC = 0.96%) adults. For esophageal and stomach cancer, incidence rates declined in more than 50% of countries for all adults while liver cancer declined slightly in younger and increased in older adults.
Commentary
There is a tremendous amount of interesting and valuable information here, but the study has some limitations. Reflecting the very different prevalence of national cancer registries between countries across the world, the database is heavily biased towards more developed nations (for example, 22 of the 42 contributing countries were in Europe) with only one African country contributing. This limits interpretation, especially when it comes to unravelling the relative contributions of dietary and socioeconomic factors. Nevertheless, these trends are consistent with local experience for many gastroenterologists – declining rates of colorectal cancer among older adults (i.e., those actually screened) in countries with robust colon cancer screening programs while this cancer increases in incidence in younger adults. While the reasons for this worrying trend are unknown, these authors speculate a possible role for the obesity epidemic. The report does not differentiate between various histological or anatomical forms of esophageal or gastric cancer, so may conceal increases in less common types, but the overall declines in these cancers are as expected and most likely related to improved nutrition and lower rates of infection with Helicobacter pylori and use of tobacco products. Other trends such as those for liver cancer (decreasing in younger and increasing in older adults) may reflect the contrasting impacts of hepatitis B vaccination, on the one hand, and the natural history of the increasingly prevalent metabolic dysfunction-associated fatty liver disease (MAFLD) on the other.
Citation
Berrington de Gonzalez A, Brayley M, Frost R, Freedman N, Gunter MJ, Jackson I, Lapitan P, Shiels MS, García-Closas M. Trends in Cancer Incidence in Younger and Older Adults : An International Comparative Analysis. Ann Intern Med. 2025;178:1677-1687.
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