Barnes-Jewish Hospital | Washington University Physicians
BENCH | 
breakthroughs from the lab

WOMEN’S HEALTH: OBESITY AND EARLY-ONSET COLORECTAL CANCER

Originally published May 2019

BY JULIA EVANGELOU STRAIT

In the United States, overall rates of new colorectal cancer cases and deaths from the disease have decreased steadily since 1980, largely owing to recommended colonoscopy screening starting at age 50. However, for reasons that remain unknown, new cases of, and deaths due to, both colon and rectal cancers have been increasing for younger adults ages 20 to 49.

obesity

Though on the rise, early-onset colorectal cancer, occurring in people younger than 50, remains relatively rare at about eight cases per 100,000 people. But because people in this age group do not receive routine screening, cases often are diagnosed at later stages of the disease, when they are much more difficult to treat.

To learn more about the increase in early-onset colorectal cancer, researchers at Washington University School of Medicine collaborated with other scientists at the Harvard T.H. Chan School of Public Health, Brigham and Women’s Hospital, and Massachusetts General Hospital at Harvard Medical School in a study looking for contributors to early-onset colorectal cancer.

The researchers analyzed data from 85,256 women ages 25 to 44 enrolled in a national study, the Nurses’ Health Study II, which began in 1989. Data included detailed information on body weight at different phases of life, as well as family and endoscopy histories, and lifestyle factors, collected at study baseline and every two to four years. Up to 2011, doctors diagnosed 114 colorectal cancer cases in participants under age 50.

At its conclusion, the study found that women who are overweight or obese have up to twice the risk of developing colorectal cancer before age 50 as women who have what is considered a normal body mass index (BMI). The study’s co-senior author, Yin Cao, ScD, a Washington University cancer epidemiologist, says, “Our findings really highlight the importance of maintaining a healthy weight, beginning in early adulthood, for the prevention of early-onset colorectal cancer.”

Researchers emphasize that this is an association study; it does not establish that increasing weight is a cause of early-onset colorectal cancer. It is possible BMI could be serving as a surrogate for other risk factors, including metabolic syndrome and diabetes, which also have been increasing at the population level. Researchers also note that more studies are needed to uncover the best ways to identify people at high risk of colorectal cancer at younger ages. And since this study was limited to women who were predominantly white, more research is needed to see if these associations remain true for men and for diverse racial and ethnic populations.

Compared with women with the lowest BMIs (18.5-22.9), women with the highest BMIs (greater than 30) had almost twice the risk of early-onset colorectal cancer. According to the Centers for Disease Control and Prevention, the normal BMI range is 18.5-24.9; BMIs from 25-29.9 are considered overweight, and BMIs greater than 30 are considered obese.

The researchers estimated that roughly 22% of early-onset colorectal cancer could have been prevented had all participants had a BMI between 18.5-24.9. On a population scale, this represents thousands of potentially preventable colorectal cancer cases among the younger population. The study further found that the higher risk of early-onset colorectal cancer associated with increasing BMI existed even among women with no family history of the disease.

The American Cancer Society recently lowered the recommended age at which most people should undergo a first screening colonoscopy. The new guidelines recommend screening beginning at age 45, down from the previous recommendation of age 50. Cao said more research is needed to see if BMI should be a factor in determining the appropriate age an individual should begin screening or complement current screening efforts.

Originally published by Washington University School of Medicine at medicine.wustl.edu/news


What is Trending: