These 17 cancers are on the rise in younger generations

Several cancers may be affecting millennials and Gen-X more than they did baby boomers, according to a new study based out of the U.S.

The study, published in The Lancet this month, found that 17 of the 34 most common cancers diagnosed between the ages of 25 to 84 are on the rise in younger people. More than half of the cancers are linked to obesity, consistent with the rise in childhood obesity among recent generations. Without proper intervention, the study's authors warned that the burden of cancer as younger generations age could not only impact those diagnosed, but also caregivers and society as a whole.

The rise in cancer rates was particularly evident in millennials born around 1990. The number of new cancers of the small intestine, kidney and pancreas was two to three times higher in people in their mid-30s than in boomers — specifically those born around 1955. 

Other trends identified in the study were sex-specific, including the incidence of liver cancers increasing among young women.

Miranda Fidler-Benaoudia, an epidemiologist at the University of Calgary and a co-author of the study, said that along with an increase in the diagnoses of several cancers, including endometrial, gallbladder and other biliary, testicular and colorectal cancers, death rates also rose.

"What we want to understand now is why are these individuals not only being diagnosed with cancer at younger ages, but why are they also facing poorer outcomes than the generations before them," she said.

The study looked at cancer and mortality data retrieved from the North American Association of Central Cancer Registries and the U.S. National Center for Health Statistics for individuals aged 25-84 from 2000 to 2019 — data that covered 94 per cent of the U.S. population. 

Ten of the 17 cancers increasing in incidence among young people were linked with obesity. The study said that since the late 1970s, the "obesity epidemic" has been affecting Americans across all age groups — with the most affected age group being those between the ages of two and 19.

There are many differences in lifestyle and health care on the Canadian side of the border. When the rate of childhood obesity hit almost 17 per cent in the U.S., Canada's rate was lower at 13 per cent, according to a 2016 study from Health Promotion and Chronic Disease Prevention in Canada. 

"While similar geographically there are a lot of differences we need to replicate this study to be sure these trends are also not happening here," said Fidler-Benaoudia.

Even for those who are a healthy weight, the study found that diet may be associated with an increased risk of cancer.

The rise in digestive tract cancers, for instance, including those of the small intestine and other cancers not associated with obesity, could point to generational changes in the types of food people are eating.

"The way we live, the way we eat, the way we prepare our foods, the way we consume our foods, all of those things have a role," said Dr. Shady Ashamalla, a surgical oncologist at Sunnybrook Health Sciences Centre's Odette Cancer Centre in Toronto.

About 10,000 Canadians under 40 were expected to be diagnosed with cancer in 2023, representing four per cent of cancers diagnosed, according to the Canadian Cancer Society.