|New Findings Offer More Complete View of Breast Cancer Gene
Mutations in U.S. Population
NIH-Supported Study Among The First to Include African Americans, Older Women
A large study funded by the National Institutes of Health today provided the
clearest picture yet of the prevalence in the U.S. population of mutations in
two genes associated with an increased risk of breast cancer. The genes are called
Breast Cancer 1 (BRCA1) and Breast Cancer 2 (BRCA2). In addition,
the study identified key predictors for assessing which women are most likely
to carry these genetic mutations.
Each year, approximately 200,000 women in the United States are diagnosed with
breast cancer. The majority of breast cancer cases are caused by genetic changes
that occur during a woman’s lifetime and not by genetic mutations inherited from
her parents. However, researchers estimate that inherited mutations play a role
in anywhere from 5 to 27 percent of all breast cancer cases. In the mid 1990s,
researchers found that mutations in the BRCA1 and BRCA2 genes
are a major cause of the hereditary form of the disease. Women inheriting these
mutations have a 40 to 85 percent lifetime risk of developing breast cancer,
as well as an increased risk of ovarian cancer.
To date, most of the studies on BRCA1 and BRCA2 mutations
have focused on families known to be at high risk for breast cancer and on women
who develop breast cancer at a relatively young age. The new study, published
today in the journal Cancer Research, looked at the prevalence and predictors
of BRCA1 and BRCA2 mutations in under-studied groups of women,
such as African Americans and older women.
“Studies of any notable size have focused almost exclusively on white women
and young women. This research clearly was needed to improve our means of assessing
the likelihood of carrying BRCA1 and BRCA2 mutations in a wider
spectrum of women,” said one of the study’s lead investigators, Elaine Ostrander,
Ph.D., chief of the Cancer Genetics Branch in the National Human Genome Research
Institute’s Division of Intramural Research. Dr. Ostrander was previously head
of the genetics program at the Fred Hutchinson Cancer Research Center, which
is the institution that led the study.
The researchers examined the prevalence and predictors of BRCA1 and BRCA2 mutations
in 1,628 women with breast cancer and 674 similar women without breast cancer,
all of whom were participants in the National Institute of Child Health and Human
Development’s (NICHD’s) Women’s Contraceptive And Reproductive Experiences (CARE)
study. The women involved in the study were white and African American women,
ages 35 to 64, who lived in the Atlanta, Detroit, Los Angeles, Philadelphia and
Seattle metropolitan areas.
“The advantages of this study include its large sample size, inclusion of under-studied
groups of women and the fact that the results are population based,” said one
of the study’s co-authors, Robert Spirtas, Dr. P.H., former chief of NICHD’s
Contraception and Reproductive Health Branch and now retired.
Researchers found that 2.4 percent of the breast cancer patients had BRCA1 mutations
and 2.3 percent had BRCA2 mutations. BRCA1 mutations were more
common among white breast cancer patients, 2.9 percent, than among African American
patients, 1.4 percent. Breast cancer patients of Jewish ancestry were also significantly
more likely to have BRCA1 mutations than non-Jewish patients, 10.2 percent
compared to 2.0 percent. For BRCA2, African American patients were slightly
more likely to have mutations, 2.6 percent, than were white patients, 2.1 percent.
Based on their findings, the researchers went on to calculate the prevalence
of BRCA1 and BRCA2 mutations in the general U.S. population.
Among white and African American women ages 35 to 64, the prevalence of BRCA1 mutations
is 0.06 percent and the prevalence of BRCA2 mutations is 0.4 percent,
the researchers estimated.
“These findings from our large, population-based study are compatible with earlier
estimates made by extrapolating from smaller studies. However, we found a slightly
lower frequency of BRCA1 mutations and higher frequency of BRCA2 mutations,” said
the study’s other lead investigator, Kathleen Malone, Ph.D., Member of the Public
Health Sciences Division at the Fred Hutchinson Cancer Center. “We think the
difference lies in the fact that earlier studies were confined mainly to whites,
and that African American women carry BRCA2 mutations more often than
The researchers also identified key predictors of whether a woman with breast
cancer is likely to carry a BRCA1 or BRCA2 mutation. Such information
is important because it can help to improve means of assessing which women may
benefit the most from genetic testing, increased breast cancer screening and
other measures aimed at early detection, treatment or prevention. The most significant
predictors for BRCA1 mutations were: Jewish ancestry, a family history
of ovarian cancer and a family history of breast cancer occurring before age
For BRCA2 mutations, researchers uncovered fewer predictors and they
had more modest effects. Among the breast cancer patients studied, the only significant
predictors of a BRCA2 mutation were early age of onset (before age 45)
in the patient herself or early onset of breast cancer in mother, sisters, grandmothers
“These findings underscore why women need to learn as much as they can about
their family health history and then share that information with their health-care
professionals. However, it must be emphasized that the presence or absence of
a predictive factor does not automatically equate with a high or low likelihood
of carrying a breast cancer gene mutation,” said NIH Director Elias A. Zerhouni,
M.D. “The majority of women with breast cancer — even those with a family
history of the disease — do not carry mutations in these genes. These predictors
need to be considered in the context of each woman’s complete family health history.”
In addition to the Fred Hutchinson Cancer Center, NHGRI, and NICHD, the team
included researchers from the National Cancer Institute; Bay State Medical Center,
Springfield, MA; the University of Pennsylvania, Philadelphia; University of
Southern California, Los Angeles; and Wayne State University, Detroit.
How to Create a Family Health History
To help people in the task of creating their family health histories, HHS offers
a free, computerized tool that organizes health information into a printout
that can be can taken to health-care professionals. The tool, called “My Family
Health Portrait,” is available at https://familyhistory.hhs.gov/.
NHGRI is one of 27 institutes and centers at the NIH, an agency of the Department
of Health and Human Services (DHHS). Additional information about NHGRI can
be found at its Web site, www.genome.gov.
The NICHD sponsors research on development, before and after birth; maternal,
child, and family health; reproductive biology and population issues; and medical
rehabilitation. For more information, visit the Web site at http://www.nichd.nih.gov/.
For more information about cancer, please visit the NCI Web site at http://www.cancer.gov,
or call NCI’s Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).
The National Institutes of Health (NIH) — The Nation's Medical Research
Agency — includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. It is the primary federal
agency for conducting and supporting basic, clinical and translational medical
research, and it investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs, visit www.nih.gov.