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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:
- BMI of 24 or under = not overweight
- BMI of 25 to 29.9 = overweight
- BMI of 30 or greater = obese
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.
Additional Resources and References
- The study, "Weight, Weight Gain, and Survival After Breast Cancer Diagnosis," discussed in this article was published in the March 1, 2005 issue of the Journal of Clinical Oncology, http://www.jco.org/
- The January 31, 2005 Journal of Clinical Oncology news release referenced in this article was posted on the Journal of Clinical Oncology website, http://www.jco.org/
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