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Dec. 7, 2007 -- Weight gain after a diagnosis of invasive breast cancer can be deadly. For every 11 pounds gained, the risk of dying from breast cancer increases by 14%, according to a new study.
"If women gained more than 22 pounds, they were 83% more likely to die of breast cancer than those who gained or lost less than 5 pounds," says Hazel B. Nichols, a doctoral student in epidemiology at Johns Hopkins Bloomberg School of Public Health in Baltimore.
She led the study, presented at the American Association for Cancer Research's Sixth Annual International Conference on Frontiers in Cancer Prevention Research in Philadelphia.
At the same meeting, other researchers reported that women with breast cancer who had high insulin levels, which tend to occur in heavier women, are also at an increased risk of death.
In the first study, Nichols and her colleagues evaluated nearly 4,000 women who had been diagnosed with invasive breast cancer in the years 1988 to 2001.
They asked the women to report their weight, weight gain, physical activity, diet, medication history, and quality of life, following them up for more than six years.
During the follow-up, 121 women died of breast cancer and 421 died from all causes, including breast cancer.
When the researchers looked at weight status and death, the risk of breast cancer death was more than twice as high among those women who were obese after the diagnosis (who may or may not have been obese before) compared with those who were normal weight during the follow-up, Nichols found.
Obesity is defined as having a body mass index or BMI of 30 or above. A 5-foot-4 woman who weighs 175 has a BMI of 30.
"We do see a trend, in general, that there is increased risk of breast cancer mortality with increasing body mass index," Nichols tells WebMD.?
Being overweight but not obese was not as risky, Nichols says. Overweight women with a BMI of 25 to 29.9, she found, were 1.3 times more likely to die from their breast cancer, an increased risk that could have been due to chance in the study.
The study did have an important limitation, Nichols tells WebMD. "We did not have extensive information on other medical conditions in later age," she says. "The extremes in risk may be related to other medical conditions that affect your risk of dying."