As cancer cases rise among younger adults, some types of the disease have higher burden than others, study finds

By Jacqueline Howard, CNN

(CNN) — Scientists have long known that cancer cases among adults younger than 50 have been on the rise in many parts of the world. But a new study suggests that certain types of cancer – breast, tracheal, bronchus and lung, stomach, and colorectal – have caused the most disease and death in this younger age group.

Globally, from 1990 to 2019, new cancer cases among younger ages increased sharply by about 79% overall, according to the study published Tuesday in the journal BMJ Oncology.

“Dietary risk factors, alcohol use and tobacco consumption were the main risk factors for top early-onset cancers in 2019,” the researchers – from Zhejiang University School of Medicine in China, Harvard University in the US and the University of Edinburgh in the UK, among other institutions – wrote in their study.

“Encouraging a healthy lifestyle, including a healthy diet, the restriction of tobacco and alcohol consumption and appropriate outdoor activity, could reduce the burden of early-onset cancer,” the researchers wrote. “It is worth exploring whether early screening and prevention programmes for early-onset cancer should be expanded to include individuals aged 40–44 and 45–49, but further systematic studies and randomised trials are necessary to make a definitive determination.”

In the United States, some national guidelines for certain cancer screenings recently have shifted to recommend to start screening at younger ages. In 2021, the US Preventive Services Task Force lowered the recommended age to start screening for colon and rectal cancers from 50 to 45. And this year in May, the USPSTF proposed in a draft recommendation that all women at average risk of breast cancer start screening at age 40 instead of 50. The recommendation is not final.

The new study included data on early-onset cancer, defined as cancer cases diagnosed in people from 14 to 49 years old, for 29 different cancer types across 204 countries, between 1990 and 2019. The data came from the Institute for Health Metrics and Evaluation’s Global Burden of Disease database.

The researchers found that the global number of new cancer cases among ages 14 to 49 increased by 79.1% from 1990 to 2019, climbing from a total of 1.82 million cancer diagnoses in that age group in 1990 to 3.26 million in 2019.

Among those cancer cases, early-onset breast cancer had the highest incidence while a type of head and neck cancer called nasopharyngeal cancer and prostate cancer appeared to have the fastest increases in incidence since 1990. The researchers found that early-onset liver cancer showed the sharpest decline during that time.

The data also revealed that the global number of cancer deaths among this younger age group increased by 27.7%, rising from 0.83 million lives lost in 1990 to 1.06 million in 2019. While that absolute number of deaths climbed, when the researchers standardized the cancer death rates by age there was a slight decrease. That’s important to note, since the absolute numbers do not account for changes in demographics such as increases in population size or aging of the population.

The top four types of early-onset cancers with the highest death toll and burden were breast; tracheal, bronchus and lung; stomach and colorectal cancers.

When examining the burden of early-onset cancer across different regions of the world, the researchers found that North America had the highest age-standardized incidence rates while the lowest were in Western Sub-Saharan Africa. The regions with the highest age-standardized death rates were Oceania, Eastern Europe and Central Asia, whereas the lowest were in the high-income Asia Pacific.

“On the whole, the more developed the country and region, the higher the incidence of early-onset cancer. The rising incidence of early-onset cancers may partially attribute to increasing uptake of screening and early detection in developed regions and countries; however, only a small number of countries and certain types of cancer,” the researchers wrote in their study.

Based on their examinations of the past three decades, the researchers projected that the global number of new early-onset cancer cases and deaths could rise by 31% and 21%, respectively, in 2030. They estimated that adults in their 40s will represent a significant proportion of those cases and deaths in the next decade.

“While increasing age remains a major non-modifiable risk factor for cancer, the incidence of early-onset cancers, largely accepted to be in adults aged under 50 years, is increasing. In addition, cancers historically perceived to be more common in older age groups are now being diagnosed in younger adults, including colorectal, breast, oesophageal, gastric and pancreatic cancers, among others,” Ashleigh Hamilton and Helen Coleman, both of Queen’s University Belfast in the UK, wrote in an editorial that accompanied the new study in BMJ Oncology.

“It is important to educate both the public and healthcare professionals regarding the possibility of certain cancers in younger adults to allow earlier diagnosis, which in turn improves outcomes,” Hamilton and Coleman wrote. “Prevention and early detection measures are urgently required, along with identifying optimal treatment strategies for early-onset cancers, which should include a holistic approach addressing the unique supportive care needs of younger patients.”

While the new study “seeks to address important questions” on the global surge in early-onset cancers, its findings align with what already has been seen in previous research, Montserrat García-Closas, a professor of epidemiology at The Institute of Cancer Research in London, said in a written statement distributed by the UK-based Science Media Centre.

“Previous reports have shown that globally, since the 1990s, there has been an increase in cancer incidence rates in the under 50s and a decrease in mortality rates, meaning more people under 50 are surviving their cancers, likely due to improvements in early detection and treatments,” said García-Closas, who was not involved in the new study.

“Most countries did not have available data on how the prevalence of risk factors like smoking or obesity changed over time,” she said in part. “This would have limited the authors ability to draw reliable conclusions about how temporal trends of these risk factors contributed to cancer incidence or mortality over time.”

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