Sister Study seeks breast cancer's unknown causes

7/30/2008, 11:45 a.m.

Dixon says those numbers need to go up.

“Because the study is focused on women who have not been diagnosed with breast cancer, it is sometimes challenging to get them to understand why it is important to participate in the study,” says Dixon. “It’s really important to think about participation in medical research as being a part of prevention, just like getting a mammogram and just like going to the doctor to get your annual exams.”

That focus on women who have not developed breast cancer makes the Sister Study unique. Dixon says most breast cancer research has been conducted using women who have already been diagnosed.

“By the time a woman is diagnosed with breast cancer, her body has already been changed by the disease and she’s probably made lifestyle and dietary adjustments,” says Dixon. “So it’s hard to determine what happened before she was diagnosed.”

Researchers believe there is much more to be learned about what causes breast cancer; fewer than 20 percent of women who get breast cancer have a family history of the disease, according to Dixon, and only about 50 percent of those who develop it fit into traditional categories of known causes.

“You can’t find a cure unless you know what is causing the disease,” says Johnson.

Or unless researchers have relevant data. Dixon, an African American, points out that much of what is now known about breast cancer comes from studies that included mostly white participants, and that information is not as effective when trying to treat African American women.

“We will never learn what causes breast cancer in women of color if we’re not well represented in the Sister Study,” she says.

Johnson enrolled in the study four years ago. She received a start-up kit in the mail that included a questionnaire for her to fill out and materials for her to use in collecting samples of her urine, toenail clippings and house dust. After she’d done that, an examiner visited her place to take her baseline measurements and blood pressure.

Now Johnson’s only responsibility is to check in with researchers once a year and give general health information, an annual update she will provide for 10 to 14 years. Once enough women enroll, the study will begin analyzing the data gleaned from participants over that span — including which participants developed breast cancer and which ones didn’t.

While less than one in five women who develop breast cancer have family histories, it is still a significant risk factor worth studying, according to Dixon .

“Because [women with sisters diagnosed with breast cancer] have high risk of developing the disease, we know that over the course of 10 years, some of these women will develop breast cancer and others won’t,” she says. “So the goal of the study is to compare the information from those women who do develop breast cancer to the information we’ve collected from the women who don’t.”

For her part, Johnson says her lifestyle didn’t change much after she found out about her sister’s breast cancer. But if the study points out new risk factors in the future, she says she would adapt.