Cancers in adults under 50 on the rise globally

Over 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 age 50), including cancers of the breast, colon, esophagus, kidney, liver, and pancreas among others, has dramatically increased around the world, with this drastic rise beginning around 1990. In an effort to understand why many more younger individuals are being diagnosed with cancer, scientists conducted extensive analyses of available data in the literature and online, including information on early life exposures that might have contributed to this trend. Results are published in Nature Reviews Clinical Oncology.

"From our data, we observed something called the birth cohort effect. This effect shows that each successive group of people born at a later time (e.g., decade-later) have a higher risk of developing cancer later in life, likely due to risk factors they were exposed to at a young age," explained Shuji Ogino, MD, PhD, a professor and physician-scientist in the Department of Pathology at the Brigham. "We found that this risk is increasing with each generation. For instance, people born in 1960 experienced higher cancer risk before they turn 50 than people born in 1950 and we predict that this risk level will continue to climb in successive generations."

To conduct this study, Ogino and lead author Tomotaka Ugai, MD, PhD, also of the Department of Pathology, and their colleagues first analyzed global data describing the incidence of 14 different cancer types that showed increased incidence in adults before age 50 from 2000 to 2012. Then, the team searched for available studies that examined trends of possible risk factors including early life exposures in the general populations. Finally, the team examined the literature describing clinical and biological tumor characteristics of early-onset cancers compared to later-onset cancers diagnosed after age 50.

In an extensive review, the team found that the early life exposome, which encompasses one's diet, lifestyle, weight, environmental exposures, and microbiome, has changed substantially in the last several decades. Thus, they hypothesized that factors like the westernized diet and lifestyle may be contributing to the early-onset cancer epidemic. The team acknowledged that this increased incidence of certain cancer types is, in part, due to early detection through cancer screening programs. They couldn't precisely measure what proportion of this growing prevalence could solely be attributed to screening and early detection. However, they noted that increased incidence of many of the 14 cancer types is unlikely solely due to enhanced screening alone.

Science Daily