Analyzing Breast Cancer Risk and Patterns
Helping older women more accurately gauge their risk of breast cancer and potentially lower that risk is the aim of a new DF/HCC project.
Dirk Iglehart, M.D. (left), Dana-Farber, and Simon Powell, M.D. (right), Massachusetts General Hospital, co-direct the Dana-Farber/Harvard Specialized Program of Research Excellence (SPORE) in Breast Cancer.
To estimate a woman's risk for breast cancer, doctors consider several factors: the age at which she entered puberty, how old she was when she had her first pregnancy, and, crucially, whether any of her close relatives have had the disease and at what age. But doctors also know there's more to consider. Research has shown that after menopause, women whose breasts appear especially dense on mammograms and who have high levels of the hormone estrogen in their blood have a higher-than-average chance of developing breast cancer. Can this information be combined with other data to help older women gain a more accurate picture of their risk for breast cancer?
In a project spanning three DF/HCC institutions, investigators are planning to do just that — and to go a step further by studying whether an anti-estrogen drug can help lower such risk. The project is one of several new collaborative studies in breast cancer. It unites researchers at Brigham and Women's Hospital (BWH) who explore health trends in large populations with scientists at Dana-Farber Cancer Institute and Beth Israel Deaconess Medical Center who test the safety and effectiveness of new drugs in patients.
"We know that the level of estrogen in the blood is a better predictor of a postmenopausal woman's chances of developing breast cancer than cholesterol is a predictor of an individual's chances of developing heart disease," says Graham Colditz, M.D., Dr.P.H., of the Channing Laboratory at BWH and a principal investigator of the new study. "But knowing estrogen's relation to breast cancer risk is only a first step. Our goal is to incorporate that knowledge into a more accurate tool for gauging breast cancer risk."
Much of the data for this part of the project will come from the Nurses' Health Study (NHS), an investigation that since 1976 has tracked the health of more than 120,000 registered nurses in the U.S. Led by Colditz, the NHS is the world's largest study of women's health patterns. Using blood samples from the study's participants, plus biannual surveys of their health, NHS investigators have found that postmenopausal women with high levels of estrogen and its chemical building blocks have four times the rate of breast cancer as women with normal levels. Other research has shown that women with highly dense breast tissue are at greater risk for breast cancer than those with less dense tissue. It's not certain why high levels of estrogen seem to raise the risk of breast cancer in older women, but scientists have a theory. Estrogen is known to stimulate the growth and division of breast cells. More estrogen means more cells are dividing, increasing the chances that an error will be made in the cells' genes, a possible first step toward cancer.
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