Researchers globally are facing a puzzling issue: why are an increasing number of young individuals developing cancers that were once thought to primarily affect older adults?
This topic was a key discussion point at two major cancer conferences this year, generating various theories. Potential culprits include ultra-processed foods, obesity, microbial toxins, and agricultural chemicals, yet a definitive answer remains out of reach.
Oncologist Kimmie Ng highlighted at the American Society of Clinical Oncology meeting in Chicago that “multiple cancers are increasing in incidence globally among individuals under the age of 50,” with most being considered sporadic and with unknown causes.
In fact, more than 9,000 cancer cases are diagnosed daily in adults under 50, as noted by epidemiologist Hyuna Sung at the American Association for Cancer Research (AACR) annual meeting in San Diego. However, combining these diagnoses might mask important details regarding their origins. “The rising incidence of cancers among young adults does not reflect a single story,” Sung mentioned, who is associated with the American Cancer Society in Atlanta.
Different Origins
The underlying data reveals various narratives. If specific cancer diagnoses suddenly increase across different age groups, it could indicate changes in detection or classification methods. For example, the definition of pancreatic cancer was broadened in the early 2010s to encompass pancreatic neuroendocrine tumors. This expansion likely contributed to the spike in diagnoses among younger individuals.
While this classification change partly explains the uptick in early-onset pancreatic cancer, Sung believes it doesn’t account for the entire phenomenon.
Conversely, the rise in cases among young people for other cancers points to an alarming trend in their actual occurrence. For example, colorectal cancer is notably on the rise: in the US, the incidence of advanced colorectal cancer jumped approximately 3% annually starting around 2010 for those aged 20 to 49, with it becoming the leading cancer-related cause of death in this age group in 2023.
There’s also an increase in uterine and liver cancer cases among young women, according to Sung. This surge seems to follow a ‘birth cohort effect,’ suggesting that people born during certain years are more susceptible than those born earlier.
Environmental Factors
Despite these alarming statistics, cancer-related deaths in those under 50 still represent a small fraction of total cancer mortality. However, the heightened risk among today’s young adults could extend into their later years when overall cancer risk escalates. “This increasing trend of cancer among young adults really signals what comes next in 20 and 30 years, when they become middle-aged and elderly,” remarked Sung.
So, what’s putting this generation at risk? One likely factor is highlighted by Andrew Chan, a gastroenterologist at Massachusetts General Hospital, who points to environmental exposures fostering metabolic diseases and obesity. “People are getting exposed to these factors at a younger age,” he stated.
While connections between colorectal and uterine cancers and obesity are recognized, Ng, who leads the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute, suggests that obesity alone doesn’t entirely explain the increase. “Many of the young patients we’ve dealt with are not obese,” she pointed out at the oncology conference. “It’s crucial to start exploring other potential exposures.”
