Study enlists sisters of cancer victims

Research: Sisters of women who have breast cancer join an effort to identify potential environmental and genetic risk factors for the disease.

Medicine & Science

October 25, 2004|By Erika Niedowski | Erika Niedowski,SUN STAFF

The key to breast cancer might lie in 50,000 sisters.

In the largest-ever study of its kind, the National Institute of Environmental Health Sciences is enrolling that many sisters of women with breast cancer in an effort to identify potential environmental and genetic risk factors for the disease.

Past research has identified other factors that increase the risk, including race and age, bearing a child relatively late in life or having no children, physical inactivity, and obesity after menopause. Women with mutations in either of the genes known as BRCA1 and BRCA2 also are more likely to develop the disease.

Still, these factors account for only 50 percent of breast cancer cases.

"We've got at least half of breast cancers unexplained," said Dale Sandler, chief of epidemiology at NIEHS and the study's principal investigator. "What we're trying to do in the Sister Study is not focus on one specific hypothesis. It's not like smoking and lung cancer [where] it's so obvious. We don't really know what it is" that causes breast cancer.

A woman who has a sister with breast cancer has about twice the risk of getting it herself. By studying sisters, the researchers hope to determine not just whether other genetic factors play a role in the development of the disease, but also whether common exposures -- to, say, certain chemicals or foods -- might influence risk.

"You and your sister have inherited genes from your parents, and so you share 50 percent of your genes," Sandler said. "That makes you much more alike than two people on the street. And so, to the extent that within those genes that you share are genes that influence your risk of breast cancer, you will have more of them."

Women who participate in the 10-year Sister Study will begin by donating blood, urine and toenail samples as well as dust from their homes. They will also fill out extensive questionnaires.

Women must be between 35 and 74 years old and live in the United States. They must have a sister -- living or deceased -- with breast cancer but must never have been diagnosed with the disease themselves.

For information, call 877-4SISTER, or visit

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