Weight and weight gain may predict breast cancer survival
Leaner women and those who maintain a healthy weight after diagnosis live longer
Boston, MA - In the latest report from the Brigham and Women’s Hospital (BWH) Nurses’ Health Study, researchers find more evidence that weight plays a key role in breast cancer survival. The study, appearing in the January 31, 2005 online issue of the Journal of Clinical Oncology, finds that women who maintain a healthy weight before diagnosis and avoid weight gain after treatment may have improved survival compared with women who are overweight or obese prior to diagnosis or who are lean and gain weight after diagnosis.
According to lead author BWH researcher Candyce Kroenke, ScD, MPH, “It is widely recognized that postmenopausal women who are overweight face a greater risk of developing breast cancer. This large study of more than 5,000 women shows that avoiding weight gain may be important to survival once a women is diagnosed.”
The study included 5,204 women with invasive breast cancer who were between the ages 30 to 55 when enrolled in the study in 1976. During almost 25 years of follow-up, 533 women died of breast cancer and 681 had a breast cancer recurrence. The researchers found that women who weighed more before they were diagnosed with breast cancer and those who were lean but gained weight after diagnosis and treatment tended to have worse survival outcomes. Intriguingly, the association was strongest in women who did not smoke.
“Including smokers in analyses may mask the true relationship between weight and survival after a breast cancer diagnosis as smoking is related to both lower levels of weight and a higher risk of death overall,” said Kroenke who is also an instructor at Harvard Medical School. “Researchers have also often speculated that obesity acts on cancer by raising the body’s levels of estrogen, particularly in postmenopausal women. However, smoking may promote the formation of less biologically active estrogens. By combining smokers and non-smokers in analyses, it may be more difficult to understand the true relationship between weight and survival. This study suggests a more complex relationship between weight and breast cancer survival than was originally considered.”
Specifically, among non-smokers, the study showed:
· Women who are overweight (BMI > 25 kg/m2) were 1.5 times as likely to die. Those who were obese (BMI > 30 kg/m2) were two times as likely to die during follow-up as women with a healthy body mass index (BMI < 25 kg/m2) before diagnosis.
· Women who gained substantial weight (>2.0 kg/m2 or an average of 17 lbs) after diagnosis had a more than 50 percent greater risk of death or recurrence compared to women who maintained their weight after diagnosis. Their risk of death or recurrence increased with increasing weight gain.
· The strongest associations between weight gain and death or recurrence were in premenopausal women, those with early stage cancer and those who were lean prior to diagnosis.
According to the American Cancer Society, the five-year breast cancer survival rate in the United States is approximately 87 percent. Many breast cancer patients report weight gain after diagnosis because of their treatments, principally the effects of chemotherapy, which can both cause fatigue leading to reduced physical activity, and reduce lean muscle tissue thereby slowing metabolism.
“Past studies have suggested relatively weak associations between weight, weight gain and breast cancer survival, but our ability to categorize by smoking status may help explain why previous studies haven’t found stronger associations,” said Kroenke. “Because smoking has been associated with lower weight and higher overall mortality, by grouping these two categories of women together other studies may have underestimated the importance of weight and weight gain on breast cancer survival. Our study suggests that battling breast cancer may be yet another reason to maintain a healthy weight. It further supports the importance of staying as active as possible and choosing a healthy diet to avoid weight gain.”
Please contact BWH Media Relations for more information at (617) 534-1600 or BWHMediaRelations@partners.org.
BWH is a 747-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare System, an integrated health care delivery network. BWH is committed to excellence in patient care with expertise in virtually every specialty of medicine and surgery. The BWH medical preeminence dates back to 1832 and today that rich history in clinical care is coupled with its national leadership in quality improvement and patient safety initiatives, dedication to educating and training health care professionals, and strength in biomedical research. With $370M in funding and more than 500 research scientists, BWH is an acclaimed leader in clinical, basic and epidemiological investigation - including the landmark Nurses Health Study, Physicians Health Studies, and the Women's Health Initiative. For more information visit www.brighamandwomens.org
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