Editorial NexoScience
Not long ago, the American Cancer Society changed a number that had stood for decades. It now recommends that people start colorectal cancer screening at 45 instead of 50. A rule built around older adults had to bend, because the disease wasn’t staying where the rule expected it to be.
Early-onset cancer has climbed almost everywhere. In 2019, about 3.26 million people aged 14 to 49 were diagnosed with cancer worldwide. That’s 79% more than in 1990. Deaths in the same age group reached 1.06 million, up by about 28% over the same three decades. The figures come from an analysis of 29 cancer types across 204 countries and territories, published in 2023 in the journal BMJ Oncology. It’s one of the few studies to map cancer in young adults on a truly global scale.
The numbers come from one enormous shared ledger. Jianhui Zhao, Mingyang Song, Shuai Yuan and their colleagues drew everything from the Global Burden of Disease 2019 study, a collaboration of more than 7,500 people in about 150 countries that estimates how often diseases strike, disable and kill. The team defined early-onset cancer as any cancer diagnosed between ages 14 and 49. Then they tracked three things: new cases, deaths and disability-adjusted life years (DALYs). DALYs add up the years lost to early death and the years lived in poor health. Think of them as the full bill a disease sends, not just the death notice.
Breast cancer sits at the top of the list. Of the 29 cancers, early-onset breast cancer had the highest rates of diagnosis, death and overall burden in 2019. Next in line for deaths came cancers of the windpipe and lungs, which the study groups together, followed by stomach cancer and colorectal cancer. Split by sex, breast cancer weighed heaviest on women and lung cancer on men.
Some less familiar cancers are rising fastest. Nasopharyngeal cancer, which starts in the upper throat just behind the nose, grew a little over 2% a year in young adults. Prostate cancer kept almost the same pace. Liver cancer went the other way and fell by close to 3% a year, the sharpest drop of any type. For deaths, kidney and ovarian cancer showed the steepest climbs.
Colorectal cancer quietly overtook stomach cancer. In 1990, stomach cancer was the most common early-onset cancer of the digestive system. Colorectal cancer made up 23.3% of those cases. By 2019 its share had grown to 36.8%, enough to take first place. East Asia saw the most striking shift: its rate of early-onset colorectal cancer more than doubled over the period, which pushed the region to the top of the ranking.
Wealth shapes the pattern in two opposite directions. The more developed a region, the more early-onset cancer it diagnosed. High-income North America had the highest rate, and the USA led every country. Western Sub-Saharan Africa had the lowest. Deaths, though, behave like a hill. They climbed with development up to a middle point on the Sociodemographic Index, the development score the Global Burden of Disease project uses to rank regions, and then rolled sharply downhill in the richest places. So the heaviest toll landed in the middle, on middle and high-middle income regions. Oceania, Eastern Europe and Central Asia recorded the highest death rates. The countries where the main cancers were growing fastest also sat in that middle band.
In poorer regions, women carry more of the weight. Across all regions, women were diagnosed more often than men. In high and middle income regions, deaths and lost years were roughly even between the sexes. In low and low-middle income regions they weren’t: early-onset cancer killed and disabled women far more than men there. Breast cancer is part of the reason. Its highest death rates showed up in exactly those regions, even though rich countries diagnose it more often.
Diet, alcohol and tobacco lead the risk list. The team also estimated how much of the burden of the four heaviest cancers traced back to known risk factors. Tobacco smoking accounted for about 41% of the burden of early-onset lung cancer. Diet accounted for roughly a third of the burden of colorectal cancer, led by diets low in milk, whole grains and calcium. For stomach cancer, smoking and salty food stood out. For breast cancer, alcohol and tobacco came first, each tied to under 5% of the burden. Here’s the thing: those small shares mean most early-onset breast cancer isn’t explained by any of the factors the analysis could measure.
More screening also means more cancer found. Part of the rise likely reflects better detection, the authors noted. Rich countries began testing for prostate-specific antigen (PSA), a blood marker of prostate trouble, in the 1990s, and that pushed up diagnoses. Mammography spread worldwide between 2005 and 2015. Still, the researchers wrote that screening can’t account for everything. Early-onset breast cancer also rose in countries without routine screening, which points to changes in childbearing, body weight, physical activity and drinking over recent decades.
The next decade looks busier still. Using a forecasting model that accounts for age, time period and generation of birth, the team projected that by 2030 the global number of early-onset cancer cases will grow by 31% and deaths by 21%. People in their 40s, from 40 to 49, will remain the bulk of patients. That’s why the authors raise the idea of extending screening programs to that age band.
The study counts cases, it doesn’t prove causes. The authors acknowledged several limits. Global Burden of Disease estimates depend on each country’s cancer registries, and in poorer nations underreporting and missed diagnoses likely hide cases. Africa’s low numbers may partly reflect missing records rather than less cancer. The risk factor estimates rest on scattered surveys from different sources and years. The cut at age 50 is arbitrary too, since the biology of a tumor doesn’t change on a birthday. Raw counts also swell as the world’s population grows. Most important, the risk factor shares are statistical links, not proof that red meat or too little milk caused any single person’s cancer. Honestly, the authors put it plainly themselves: the reason for the rising trend “is still unclear.”
Real answers will take years of following people. The researchers call for prospective life-course cohort studies, which track people from early life onward to see which exposures come before a diagnosis. They also argue that each country should shape its prevention plans around its own mix of early-onset cancers. Whether screening should start in the early 40s is, in their words, a question that further systematic studies and randomized trials will have to settle.
Source: Zhao J, Xu L, Sun J, Song M, Wang L, Yuan S, et al. “Global trends in incidence, death, burden and risk factors of early-onset cancer from 1990 to 2019.” BMJ Oncology, 2023. DOI: 10.1136/bmjonc-2023-000049
This article summarizes published scientific research for general information. It is not medical advice and does not replace consultation with a qualified health professional.
