Cancers in adults under 50 on the rise worldwide

In recent decades, more and more adults under the age of 50 are developing cancer. A study conducted by researchers from Brigham and Women’s Hospital reveals that the incidence of early-onset cancers (those diagnosed before the age of 50), including cancers of the breast, colon, esophagus, kidney, liver and pancreas, has increased significantly in worldwide, with this drastic increase beginning around 1990. In order to understand why more and more younger people are being diagnosed with cancer, scientists conducted extensive analyzes of data available in the literature and online, including information on early exposures that may have contributed to this trend. The results are published in Nature reviews clinical oncology.

“From our data, we observed what is called the birth cohort effect. This effect shows that each successive group of people born later (say, a decade later) has a higher risk of developing cancer later in life, likely due to risk factors they were exposed to in a young age,” explained Shuji Ogino, MD, Ph.D.professor and doctor-researcher at Department of Pathology at Brigham. “We found that this risk increases with each generation. For example, people born in 1960 had a higher risk of cancer before they turned 50 than people born in 1950 and we expect this level of risk to continue to increase over generations.

To conduct this study, Ogino and lead author Tomotaka Ugai, MD, PhD, also from the Department of Pathology, and their colleagues first analyzed global data describing the incidence of 14 different types of cancer which showed an increase in incidence in adults before the age of 50 from 2000 to 2012. Next, the team searched for available studies that looked at trends in possible risk factors, including early life exposures in the general population. Finally, the team reviewed the literature describing the clinical and biological tumor characteristics of early cancers compared to late cancers diagnosed after 50 years.

In a comprehensive review, the team found that the early life exposome, which encompasses diet, lifestyle, weight, environmental exposures and microbiome, has changed significantly over the past few decades. Thus, they hypothesized that factors such as Westernized diet and lifestyle could contribute to the early cancer epidemic. The team recognized that this increased incidence of certain types of cancer is, in part, due to early detection through cancer screening programs. They could not accurately measure how much of this growing prevalence could be attributed solely to screening and early detection. However, they noted that increased incidence of many of the 14 cancer types is unlikely solely due to improved screening alone.

Possible risk factors for early cancer included alcohol consumption, sleep deprivation, smoking, obesity and diet food. Surprisingly, researchers have found that while adult sleep duration hasn’t changed drastically over the decades, children sleep far less today than they did decades ago. Risk factors such as highly processed foods, sugary drinks, obesity, type 2 diabetes, sedentary lifestyle, and alcohol consumption have all increased dramatically since the 1950s, which researchers say accompanied an altered microbiome.

“Of the 14 types of rising cancers we studied, eight were related to the digestive system. The food we eat feeds the microorganisms in our gut,” Ugai said. “Diet directly affects the composition of the microbiome, and possibly these changes can influence disease risk and outcome.”

One of the limitations of this study is that the researchers did not have enough data from low- and middle-income countries to identify trends in cancer incidence over decades. In the future, Ogino and Ugai hope to continue this research by collecting more data and collaborating with international research institutes to better monitor global trends. They also explained the importance of conducting longitudinal cohort studies with parental consent to include young children who can be followed for several decades.

“Without such studies, it is difficult to identify what a person with cancer did decades ago or when one was a child,” Ugai explained, “Because of this challenge, we aim to conduct more longitudinal cohort studies in the future where we follow the same cohort of participants over their lifetime, collecting health data, possibly from electronic health records, and biological samples at specific time points. is not only more cost effective given the many types of cancer to be studied, but I believe it will give us more accurate information about cancer risk for generations to come.

Funding: SO’s work is supported in part by grants from the U.S. National Institutes of Health (R35 CA197735 and R01 CA248857) and the Cancer Research UK Cancer Grand Challenge Award [6340201/A27140]. TU’s work is supported by grants from the Prevent Cancer Foundation, the Japan Society for the Promotion of Science, and the Mishima Kaiun Memorial Foundation.

Article quoted: Ugai T et al. “Is early cancer an emerging global epidemic? Current evidence and future implications. Nature Reviews Clinical Oncology DO I: 10.1038/s41571-022-00672-8

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