DUARTE, Calif., June 7 (UPI) -- Women who have a healthy body weight before and after a breast cancer diagnosis have better odds than others of beating the disease, U.S. researchers say.
"This relationship between dying and being obese or overweight may depend on whether the type of breast cancer is hormonally dependent," lead author Christina Dieli-Conwright, assistant research professor at City of Hope National Medical Center in Duarte, Calif., says in a statement.
The research involved participants in the large California Teachers Study who, from 1995 to 2006, received a diagnosis of invasive breast cancer -- cancer that has spread beyond the breast ducts.
About 4,000 women were studied. Of them, 262 died of breast cancer by 2007. Obesity was defined as a body mass index of 30 or higher.
Women who were obese at baseline had a 69 percent higher risk of dying of their breast cancer than did non-obese women. The same increased mortality was present in women who were overweight -- BMI of 25 to 29 at age 18.
The researchers also found the higher the BMI, the greater the risk of dying of breast cancer for women with estrogen-dependent cancer. But there was no such link in women with estrogen-negative breast cancer.
Women who are obese or overweight tend to have higher levels of circulating estrogen, which likely explains this difference, Dieli-Conwright said.
The findings were presented at The Endocrine Society's 93rd annual meeting in Boston.