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Body Mass Index Impacts Breast Cancer Prognosis

February 5, 2010

Written By Mary Alice Hartsock
Reviewed By Carrie Tompkins Stricker, PhD, RN

After breast cancer treatment, having a body mass index (BMI) of more than 25 (being overweight or obese) is related to higher likelihood of distant metastasis and poorer survival rates, results of a recent study indicate.

The study, presented at the 32nd Annual San Antonio Breast Cancer Symposium in December, was a retrospective study of nearly 19,000 women diagnosed with early-stage breast cancer in Denmark who were followed for up to 30 years after diagnosis.

Study Design

The scientists gathered data on 53,816 women from the Danish Breast Cancer Cooperative Group database. Scientists knew the height and weight of 18,967 of the women. They used this information to determine their BMI, a measure that helps define healthy and unhealthy body weights, approximates body fat and is used to predict risk for disease.

The U.S. Department of Health and Human Services National Institutes of Health considers a person with a BMI of less than 18.5 to be "underweight" and a person of "normal weight" to have a BMI of 18.5-24.9. The NIH designates a person with a BMI between 25-29.9 as "overweight," and a person with a BMI of more than 30 as "obese."

Study Findings

Compared to women with a BMI of less than 25, women with a BMI over 25 were older, more often postmenopausal, and had larger tumors, more positive lymph nodes, more invasion of cancer cells into breast tissue and lymph nodes, and more grade III cancers, which indicates more aggressive growth and characteristics of the cancer cells.

Women who were overweight or obese (BMI of 25 or more) had a greater risk over time of developing metastatic breast cancer, or cancer that has traveled away from the breast to other parts of the body such as the bones, liver, lungs or brain. The risk for loco-regional recurrence, or recurrence in the same area as the original breast cancer, did not increase based on BMI.

In addition, the risk of dying from breast cancer was higher for women with a BMI of 25 or above than for those with a lower BMI.

Within the first ten years after the original diagnosis, chemotherapy and hormonal therapy appeared to work similarly well in people of any BMI. But after ten years, the treatment effect did not last as well for obese women with a BMI of 30 or above, as they had poorer survival in spite of receiving treatment.

What Does This Study Mean for Me?

This study suggests that managing your weight could protect you from a recurrence of breast cancer, or it could help your adjuvant (post-surgical) treatment last longer than it would otherwise. Exercise also can protect you from other diseases and even improve your mood.

Starting an exercise routine—or continuing one while you are recovering from treatment—can be challenging, but there are many simple steps you can take to get started. Talk with your doctor or nurse about a physical fitness routine, and choose fruits, vegetables and lean protein. Develop a follow-up care plan with your healthcare team, and be diligent about getting your regular screening mammograms and other follow-up tests. Go to the NIH website to calculate your BMI and to learn more about living a healthful lifestyle. Read an article on Using Fitness and Exercise for Coping in our Spring 2010 issue of Insight.

Ewertz, M. et al. Effect of Obesity on Prognosis after Early Breast Cancer. Presented at the 32nd Annual San Antonio Breast Cancer Symposium. December 10, 2009. Abstract 18.

Read more about the link between BMI and breast cancer prognosis.