More young adults are getting cancer. Researchers are racing to understand why

HEALTH

Dr. Frank Frizelle has operated on countless patients in his career as a colorectal surgeon. But there’s one case that stayed with him.

In 2014, he was treating a woman in her late 20s suffering from bowel cancer—already a rare situation, given her age. But it became even more unusual when her best friend visited her in the hospital and told Frizelle that she had many of the same symptoms as his patient. Subsequent testing revealed that his patient’s friend had a lesion that, had it not been caught early, likely would have become cancerous. “That really brought it home to me—how it’s much more common than you think,” says Frizelle, a professor of surgery at the University of Otago in New Zealand.

Still, like any good scientist, Frizelle was skeptical. Was it simply a fluke that he kept treating strikingly young patients? Or was his practice one tiny data point in a larger trend?

He found his ...