Colorectal Cancer Coverage from Every Angle

Why Are More Patients Younger Than Age 50 Developing Colorectal Cancer?

By: Anna Nowogrodzki
Posted: Friday, August 30, 2019

The rates of colorectal cancer in Canadian men and women younger than age 50 have been increasing in the past decade and a half, according to a new study in the journal JAMA Network Open. Darren R. Brenner, PhD, of the University of Calgary, and colleagues conducted the research on national trends in colorectal cancer incidence.

“Every year, we keep seeing the increase in colorectal cancer among young people, and it is very alarming,” Dr. Brenner told The New York Times. “We need to understand why this trend is occurring in young people in order to prevent it.”

The authors studied the 688,515 incident colorectal cancers in the Canadian national cancer registry between 1969 and 2015. The incidence of colorectal cancer in men younger than age 50 increased from 2006 to 2015, with an annual percentage change of 3.47%. Among women younger than age 50, the incidence of colorectal cancer increased from 2010 to 2015, with an annual percentage change of 4.45%. The analysis indicates that the trend seems to be driven by people between the ages of 40 and 49. The rates of colorectal cancer continue to decrease in those older than age 50.

Researchers are not sure why more young adults are developing colorectal cancer, but there seems to be an association between birth cohort (broken down into 5-year groups) and higher incidence. This connection suggests that the cause may be early life exposure or an exposure that accumulates over the years, rather than detection bias. Similar previously published data from the United States suggest that perhaps there is a common exposure in North America.

In the United States, guidelines have been updated to recommend screening for colorectal cancer beginning at age 45. Before experts in Canada decide whether to do the same, the authors recommended more research on risk factors and how changing the guidelines would affect incidence and mortality. For instance, screening younger people may prove to be unnecessarily invasive, may divert resources from higher-risk populations, or may increase colonoscopy wait times for higher-risk populations.

Disclosure: The study authors reported no conflicts of interest.

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