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A recent study suggests that women who are overweight prior to a diagnosis of breast cancer, or those who gain weight during treatment, are at an increased risk of having their breast cancer return and are more likely to die from the disease, compared to women of a healthy weight. While past studies have examined the issues of weight and breast cancer, this study of over 5,200 nurses is one of the first to separate smokers from non-smokers. The researchers estimate that 60% of women gain weight during breast cancer treatment, often as the result of treatments such as chemotherapy, and encourage physicians and patients to pay careful attention to the issue of weight to increase the chances of a successful treatment. To examine the issue of weight and breast cancer survival, Dr. Candyce H. Kroenke from the Harvard Medical School and her colleagues studied lifestyle and medical history information of 5,204 nurses who had been diagnosed with breast cancer between 1976 and 2000. The nurses were a subset of over 121,700 female nurses who had participated in the Nurses' Health Study, a large study that followed the women over time to study their health. To calculate weight, the researchers obtained the women's body mass index (BMI). BMI measures a person's total body fat based on weight and height. It is derived by multiplying a person's weight in pounds by 703 and then dividing it twice by the person's height in inches. According to federal guidelines:
Click here to view a table that calculates BMI based on height and weight. The researchers noted changes in the women's weight before and after a breast cancer diagnosis. Women were classified in one of four categories: losing weight, maintaining weight, gaining a modest amount of weight, and gaining a substantial amount of weight. The results of the study showed that women who were overweight before they were diagnosed with breast cancer had a higher chance of dying from breast cancer. This was especially true for women who had never smoked. Women who had never smoked and were overweight at the time of their diagnosis were nearly twice as likely to die from breast cancer as women who had never smoked and maintained healthy body weights. Furthermore, weight gain after a breast cancer diagnosis was also associated with poor outcomes. Women who never smoked and gained an average of 17 pounds were 1.5 times more likely to experience a return of their breast cancer or die compared to women who did not gain weight. This study is one of the first to differentiate between smokers and nonsmokers when examining the issue of weight and breast cancer survival. "Combining smokers and non-smokers in analyses may mask the true relationship between weight and survival after a breast cancer diagnosis, since smoking is generally related to both lower levels of weight and a higher risk of death overall," said Dr. Kroenke in a Journal of Clinical Oncology news release. She added, "Researchers have also speculated that obesity acts on cancer by raising the body's levels of sex hormones such as estrogen, particularly in post-menopausal women. However, since smoking may promote the formation of less biologically active estrogens, it may be more difficult to understand the relationship between weight and breast cancer when combining smokers and non-smokers in a study. This study suggests a more complex relationship between weight and breast cancer survival than was originally considered." According to the researchers, many women struggle with weight gain during breast cancer treatment, sometimes as effects of the treatments themselves. Dr. Kroenke is beginning to look at ways that weight loss during breast cancer treatment may impact survival. At the moment, the researchers encourage doctors and patients to be aware of the negative effects of heavy weight and weight gain on breast cancer survival and recurrence and take steps to try to maintain a healthy weight before, during, and after treatment.
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