New Data Confirm Lifestyle Changes Can Dramatically Reduce Risk for Breast Cancer

From Medscape Medical News
Roxanne Nelson

September 3, 2009 — New data have confirmed that lifestyle factors play a significant role in the risk for breast cancer. An updated version of the American Institute for Cancer Research/World Cancer Research Fund's (AICR/WCRF) report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, reaffirms that factors such as maintaining a healthy weight, breastfeeding, exercising regularly, and limiting consumption of alcoholic beverages can reduce the risk for breast cancer.

The 2007 report is considered to be the most comprehensive scientific analysis of cancer prevention and causation ever undertaken, as previously reported by Medscape Oncology. The original paper reviewed 873 studies on breast cancer, and since that time, information from 81 new breast-cancer-related studies has been added to the database.

"This study represents the clearest picture we have ever had on how lifestyle affects a woman's risk of breast cancer," said Martin Wiseman, MD, medical and scientific adviser for AICR and WCRF, in a statement.

By maintaining a healthy weight, being physically active, and limiting the amount of alcohol they drink, women can dramatically reduce their risk.
"We are now more certain than ever that by maintaining a healthy weight, being physically active, and limiting the amount of alcohol they drink, women can dramatically reduce their risk," he added.

An AICR policy report issued in February 2009 estimated the percentage of cancers that could be prevented by incorporating the recommendations of the 2007 report. Overall, the report concluded that about one third of the most common cancers could be prevented by following AICR recommendations on body weight, physical activity, and diet.

They reported that 38% of cases of breast cancer in the United States could be prevented through diet, activity, and healthy weight. Based on figures from the American Cancer Society, that percentage extrapolates to about 70,000 new cases of breast cancer prevented each year.

Continuous Update Project Adds to Research

The report on breast cancer is part of the Continuous Update Project, the long-term goal of which is to continuously update the findings of the AICR/WCRF 2007 report. "When we published our 2007 report, we knew that we wanted to keep it a living document, so that its recommendations could always reflect the latest science without going out of date," explained Glen Weldon, director of communications at AICR. "That's what the Continuous Update Project is about."

For the Continuous Update Project, a smaller expert panel will collect and analyze new reports and combine the new data with the those from studies already in the database. "This will be done on a cancer-by-cancer basis," Mr. Weldon told Medscape Oncology. "Breast cancer was the most studied cancer in the years since the 2007 report, so that was the one we started with."

An independent systematic literature-review team identified an additional 81 breast cancer studies that met the criteria for inclusion. The expert panel then reviewed the new data, combined evidence, and determined that the new data only strengthened the 2007 report's conclusions.

Breast Feeding, Body Weight, Alcohol Consumption Affect Risk

In the updated chapter on breast cancer, the panel reached several conclusions regarding lifestyle/diet and breast cancer risk. They found "convincing evidence" that:

lactation protects against breast cancer at all ages
alcoholic drinks are a cause of breast cancer at all ages, and
body fatness is a cause of postmenopausal breast cancer.
In addition, there is convincing evidence that factors that lead to greater attained adult height or its consequences are a cause of postmenopausal breast cancer. The authors clarify that although adult attained height is unlikely to directly modify the risk for cancer, it is "a marker for genetic, environmental, hormonal, and nutritional factors affecting growth during the period from preconception to completion of linear growth."

Physical activity probably protects against postmenopausal breast cancer, and there is limited evidence suggesting that it protects against premenopausal breast cancer, the experts note.

Based on these conclusions, the AICR recommends the following for reducing the risk for breast cancer:

Because of the link between excess body fat and cancer, the goal is to be as lean as possible within the normal range of body weight.

Be physically active as part of everyday life.

Limit alcohol consumption to 1 drink per day for women (2 drinks for men).

Mothers should breastfeed exclusively for up to 6 months and then add other liquids and foods. Evidence is convincing that mothers who breastfeed reduce their risk for breast cancer, and there is also probable evidence that children who are breastfed have a lower risk of gaining excess weight as they grow.

World Cancer Research Fund/American Institute for Cancer Research. The Second Expert Report, Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective. Washington, DC: AICR; 2009.