Obesity Ups Women’s Colon Cancer Risk

Oct. 15, 2007 (Philadelphia) -- Obesity more than doubles a woman’s risk of developing colon cancer or growths that can lead to colon cancer, researchers say.

That puts obesity as women’s No. 1 risk factor for the disease, a study of more than 1,200 women suggests.

Women who are heavy smokers or over age 69 are also at increased risk for having potentially precancerous polyps or colon cancer, says researcher Joseph C. Anderson, MD, associate professor of medicine at Stony Brook University in Stony Brook, N.Y.

Both factors approximately double the risk of having the growths or cancer, he tells WebMD.

“What I really want my patients to know is that obesity is a risk factor. It’s a risk that is increasing with more and more Americans being obese. And it’s a risk that is modifiable,” he says.

Obesity No. 1 Risk Factor

For the study, presented at the annual meeting of the American College of Gastroenterology (ACG), Anderson and colleagues examined data from 1,252 women who underwent colonoscopy.

About 10% had cancer, multiple polyps, or large or particularly abnormal growths that would likely grow into cancer if not removed.

Anderson says that obesity, defined as a body mass index (BMI) of 30 or higher, accounted for 20% of the significant growths. Being over age 69 accounted for 16% more of the growths. Heavy smoking -- defined as smoking more than 10 pack-years (a pack year is the number of packs smoked in a day times the number of years the person has smoked), being a current smoker, or having quit in the past 10 years -- accounted for 15% of the significant growths.

Women who had smoked less than 10 pack-years or who had quit more than 10 years ago were not at significantly increased risk.

Obese Women Need to Be Screened

The findings underscore the need for obese women to get screened for colorectal cancer, says ACG President David A. Johnson, MD, a gastroenterologist at Eastern Virginia Medical School in Norfolk.

“If a woman is reticent about being screened, she needs to consider that her risk is a lot higher than that of women of normal weight,” he says.

Anderson adds that if future studies confirm the findings, obese women might want to be screened more frequently or starting at an earlier age than is currently recommended.

Current guidelines, developed by the U.S. Multi-Society Task Force on Colorectal Cancer and the American Cancer Society, recommend that most people be screened every 10 years starting at age 50.