Obesity Raises Breast Cancer Death Risks
Obese Women More Likely to Die From Breast Cancer Diagnosed in Early Stages
Sept. 21, 2004 -- Women who are obese at the time their breast cancer is diagnosed may be as much as five times more likely to die of the disease, even when it's caught in the early stages.
A new study suggests that a woman's weight at the time of breast cancer diagnosis may have a major effect on her risk of death from the disease. The findings also suggest that the higher risk of death due to breast cancer associated with obesity may be related to whether or not the tumor depends on estrogen to grow.
Breast cancers are classified as estrogen-receptor (ER) positive or negative depending on their sensitivity to estrogen. Breast cancers with estrogen receptors are referred to as ER-positive, and those without are referred to as ER-negative. Estrogen-receptor positive breast cancers are more common.
The study showed that women in the upper 50th percentile of body weight with early stage ER-negative breast cancer were five times as likely to die of the disease compared with women in the bottom half with ER-positive breast cancer.
Researchers say the results suggest that overweight women diagnosed with breast cancer should be advised to lose weight in order to improve their chances of surviving the disease.
Obesity Increases Breast Cancer Risk
In the study, published in the September issue of the Archives of Surgery, researchers analyzed the medical records of 1,376 women aged 24 to 81 who were diagnosed with breast cancer between 1988 and 1995 in southern California.
The women were followed for an average of nearly seven years after their diagnosis. During that time, 246 women died from breast cancer.
Body weight at the time of diagnosis was only weakly associated with breast cancer death overall.
But when researchers looked only at those women who were diagnosed in the early stages of the disease, they found a trend of increasing risk of death associated with increased body weight. Compared with women who weighed 133 pounds or less at the time of diagnosis, women who weighed more than 175 pounds were more than twice as likely to have died of breast cancer.
No such trend was found among women who were diagnosed during the later stages of breast cancer.
The study also found that estrogen receptor status was also associated with the women's risk of death due to breast cancer. The risk of dying was nearly 3.5 times higher for heavier women with ER-negative cancers compared with thinner women with ER-positive cancers, regardless of the stage of diagnosis.
Researchers say the findings support a growing number of studies that have shown that obesity at the time of breast cancer diagnosis negatively affects survival. They say obesity may increase breast cancer risks by affecting levels of insulin, insulin-like growth factor, and leptin, which are substances found in higher levels in obese women.
Obesity may also reflect other factors, such as poor nutrition and lower physical activity, that are also associated with poorer health.