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How Much Does Lifestyle Affect Breast Cancer Risk?

Study Suggests Weight, Drinking Habits, and Physical Activity Account for Small Portion of Overall Risk

Analyzing Cancer Risk continued...

"The really key factors for developing breast cancer are family history and increasing age. All of the other factors are relatively weak," says Ruth O' Regan, MD, an associate professor at Emory University's Winship Cancer Institute in Atlanta.

"These modifiable factors kind of fit into those slightly weaker factors," she says. "If you're at average risk, this is sort of an encouraging paper."

Experts are quick to add that beyond breast cancer risk, there are plenty of other reasons -- heart disease and diabetes among them -- to stay slim, get regular exercise, and have a moderate alcohol intake.

And they point out that lifestyle factors do make more of an impact, however, when a woman has more things in her breast cancer risk profile that she can't change.

According to the study, a 65-year-old woman with a family history of breast cancer has a 13.8% chance of developing breast cancer within the next 20 years. If she maintains a normal body weight (BMI under 25), exercises for at least two hours each week, and stops drinking alcohol, her absolute risk drops by 3.2%, to 10.6%, or a 23% drop in relative risk.

A 65-year-old woman who has the highest numbers of non-modifiable risk factors has a 20-year absolute risk of getting breast cancer of 18.6%. By exercising, watching her weight, and not drinking alcohol, she cuts that risk by 4.1%, for a 22% decrease in her relative risk, the study found.

Perspective on Cancer Risk

Experts praised the paper for adding some needed perspective to breast cancer risk prediction.

"Counseling for personal risk of breast cancer is really difficult, and I think this was a really, really well done paper," says Jennifer Litton, MD, assistant professor and a breast medical oncologist at the University of Texas, M.D. Anderson Cancer Center in Houston.

Litton cautions that the study was conducted in Italian women, who have slightly different risks and rates of breast cancer compared to Americans. "It's in a different population, and different populations and cultures have different risk factors and chances of developing cancer, so as far as how transferable it is to the United States will need to be seen," she says.

"I think this may provide us a very interesting tool, another aid when we're counseling patients, because there's so much we don't have control over," Litton says, "For the things we can change, I think it's helpful to understand."

Other experts, and the study researchers, point out that beyond individual risk, these kinds of models can also show the impact that relatively small personal changes can make to larger populations.

For example, the study found that in a population of 1 million women, a 1.6% reduction in absolute risk would translate to 16,000 fewer cancer cases.

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