Why are so many young people getting cancer? What the data say

Clues to a modern mystery could be lurking in information collected generations ago.

Of the many young people whom Cathy Eng has treated for cancer, the person who stood out the most was a young woman with a 65-year-old’s disease. The 16-year-old had flown from China to Texas to receive treatment for a gastrointestinal cancer that typically occurs in older adults. Her parents had sold their house to fund her care, but it was already too late. “She had such advanced disease, there was not much that I could do,” says Eng, now an oncologist at Vanderbilt University Medical Center in Nashville, Tennessee.

Eng specializes in adult cancers. And although the teenager, who she saw about a decade ago, was Eng’s youngest patient, she was hardly the only one to seem too young and healthy for the kind of cancer that she had.

Thousands of miles away, in Mumbai, India, surgeon George Barreto had been noticing the same thing. The observations quickly became personal, he says. Friends and family members were also developing improbable forms of cancer. “And then I made a mistake people should never do,” says Barreto, now at Flinders University in Adelaide, Australia. “I promised them I would get to the bottom of this.”

It took years to make headway on that promise, as oncologists such as Barreto and Eng gathered hard data. Statistics from around the world are now clear: the rates of more than a dozen cancers are increasing among adults under the age of 50. This rise varies from country to country and cancer to cancer, but models based on global data predict that the number of early-onset cancer cases will increase by around 30% between 2019 and 2030. In the United States, colorectal cancer — which typically strikes men in their mid-60s or older — has become the leading cause of cancer death among men under 50. In young women, it has become the second leading cause of cancer death.

As calls mount for better screening, awareness and treatments, investigators are scrambling to explain why rates are increasing. The most likely contributors — such as rising rates of obesity and early-cancer screening — do not fully account for the increase. Some are searching for answers in the gut microbiome or in the genomes of tumours themselves. But many think that the answers are still buried in studies that have tracked the lives and health of children born half a century ago. “If it had been a single smoking gun, our studies would have at least pointed to one factor,” says Sonia Kupfer, a gastroenterologist at the University of Chicago in