Women who know the angry, helpless feeling of watching a sister face breast cancer have gained a new, active, and personal way to fight the disease with the nationwide launch of The Sister Study. It's an ambitious, wide-ranging search for possible environmental and genetic causes of breast cancer using questionnaires and, among other variables, samples of household dust.
Sister Study directors at the National Institute of Environmental Health Sciences (NIEHS) hope to enroll 50,000 women from all walks of life, ages 35-74, who've had a sister with breast cancer, but have not had the disease themselves.
More than 215,000 new cases of breast cancer are expected this year, and despite great progress in treatments and survival rates, scientists do not yet fully understand what causes the disease or why it occurs more frequently in certain parts of the US.
African-Americans and other minority women are strongly encouraged to join the study so the results will apply to all women. And women 60 and older are greatly needed, too. Sister Study researchers will compare women who do and do not develop breast cancer over the 10-year course of the study.
"We're going to do more than any one else has ever done to find answers," said the lead investigator Dale Sandler, PhD. "I'm hoping that we'll find something that women can do to prevent cancer or put some common fears to rest," she said.
Some currently-known factors that increase a woman’s risk of developing breast cancer include a family history of the disease, early onset of menstruation, having no children or older age at first pregnancy, and being overweight or obese. Yet, many women diagnosed with breast cancer have none of these risk factors. That was the case for Vernal Branch, who discovered a small lump in her breast at age 45.
"At the time of my diagnosis I thought I had none of the known risk factors, except just being a woman," said Branch, now a health educator for The Sister Study. In the 3 weeks between discovering the pea-sized lump and having a mastectomy, Branch's tumor grew quickly to the size of a golf ball.
What causes such a fast-growing tumor in an otherwise healthy 45-year-old black woman? Sandler and her colleagues want the answer to that question as soon as possible. African-American women overall are about 13% less likely to develop breast cancer than whites, but they are more likely to die from it, according to the ACS publication Cancer Facts & Figures for African-Americans, 2003-2004.
In addition, for reasons not yet understood, one age group of black women – those under age 40 – have a higher incidence of breast cancer, as well as a higher death rate than their white counterparts.
About 2 years after her own diagnosis, Branch unearthed a family secret that can be very important to younger generations: Branch's grandmother had two sisters with breast cancer. ACS encourages women with a strong family history of the disease to talk with their doctors about early and frequent screening exams.
Whether a woman's DNA or her environment causes breast cancer is still very much an open question. Research shows that hormones play a role in breast cancer. And scientists have found two genes passed down through families that cause breast cancer: BRCA1 and BRCA2. But those genes only cause 5%-10% of breast cancer cases.
Elizabeth Ward, PhD, director of surveillance for the American Cancer Society, says that there may be other, more common genes that interact with environmental exposures to cause the disease.
"However, at this point, there are more concerns than solid evidence on the potential effects of chemical or other environmental exposures," said Ward. "We know that exposure to high levels of radiation and certain chemicals can cause breast cancer, based on epidemiologic and laboratory studies, but it's very difficult to detect the effects of low level, common exposures in the general population, especially if the critical time period for such exposures is early in life."
The Sister Study will collect samples of blood, urine, toenails, and household dust to measure many different bio-markers of environmental exposures. (They stress that all personal information will be kept confidential.)
Explained Sandler, "As we age, we accumulate exposures. If those exposures damage breast tissue, [then] the more times you challenge that tissue, the more likely it is to lead to breast cancer." She added, "We're particularly interested in the in utero period, the time around the onset of the menstrual period, and the time of the first pregnancy."
Ward confirms there may be vulnerable time periods in a woman's life: "We know from studies of atomic bomb survivors that women exposed to high doses of radiation during adolescence had a higher risk of breast cancer than those exposed later in life."
Following the sisters of women diagnosed with breast cancer, rather than average women, may shorten the time it takes to find answers. The healthy sisters share genes, and sometimes lifestyles and communities, with their siblings touched by breast cancer – so whatever causes the disease will probably be more common in this group. And, their risk for breast cancer is about twice the national average.
"Women who participate in the study are actually doing something about breast cancer," said Sandler. "They can feel good about that."
Vernal Branch will reach age 55 and the 10-year survival mark this October – anniversaries that make her thankful to be alive and determined to bring many, many women to the Sister Study as participants or volunteers. "I tell people, 'This may not help you, but it's going to help your daughters and granddaughters.'
"I'm expecting my first grandchild – it's a little girl – and I want to see changes for that generation."
Sister Study participants will:
- Fill out a questionnaire.
- Meet briefly with an examiner to provide samples of blood, urine, toenails, and house dust.
- Complete a health update each year for 10 years.
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