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The Sister Study
and the Two Sister Study

The Sister Study

What causes one woman to develop breast cancer and not another? Researchers know that things like age, race, physical activity, weight, alcohol use, and use of hormone therapy after menopause, as well as other factors may affect a woman’s risk of breast cancer. But a lot of women who have one or more of these risk factors never develop the disease. In contrast, many women with breast cancer have no known risk factors (other than age and being female, which are the main risk factors for breast cancer).

In 2004, researchers from the National Institute of Environmental Health Sciences (NIEHS) started recruiting women to be part of the Sister Study. Enrollment was completed in March of 2009, so no one else can sign up. This is a long-term, nationwide study looking at how a woman’s genes and environment might affect her chances of getting breast cancer.

The Sister Study includes 50,000 women, ages 35-74. The women have not had breast cancer themselves, but their sisters have. Over the 10 years of the study, these women will complete telephone interviews and fill out questionnaires. They will have their blood drawn and give samples of urine, toenail clippings, and household dust. They will also complete health updates each year. Researchers will then compare study members who go on to develop breast cancer with those who do not develop the disease. In this way, they hope to learn more about possible environmental and genetic causes of breast cancer, as well as ways to prevent the disease.

The NIEHS is funding the research, which is being led by two NIEHS scientists, Dale Sandler, PhD, and Clarice Weinberg, PhD.

To find out more about the study, visit www.sisterstudy.org or call 1-877-4SISTER (1-877-474-7837).

Looking at families: The Two Sister Study

In August 2008, National Institute of Environmental Health Sciences (NIEHS) researchers launched the Two Sister Study, which builds on the work of the Sister Study. The Two Sister Study will focus on women who develop breast cancer at a young age. Enrollment was through invitation only: some breast cancer survivors whose cancer-free sisters were already enrolled in the Sister Study were eligible to join if they were diagnosed less than 4 years earlier and were under age 50 at the time.

The goal of 2,000 survivors has been reached for the Two Sister Study, and enrollment closed in December 30, 2010. These volunteers provided detailed health information and updates, as well as spit (saliva) samples for DNA analysis. NIEHS researchers are comparing the sisters with and without breast cancer and looking for possible genetic and environmental links. The sisters’ parents were also invited to take part. The research is being funded by the Susan G. Komen for the Cure and the NIEHS. It’s being directed by Weinberg, Sandler, and Lisa DeRoo, PhD, also of NIEHS.

To find out more about this study, visit www.sisterstudy.org and click on “Two Sister Study,” or visit http://sisterstudy.niehs.nih.gov/English/2sis.htm. You can also call 1-877-4SISTER (1-877-474-7837).

If you want to do more

If you want to help researchers learn more about what causes breast cancer, but are not part of the Sister Studies, contact the following organizations. They can help you find out about research studies you may be eligible for:

National Cancer Institute

American Cancer Society Cancer Prevention Study 3

American Cancer Society Clinical Trials Information

Dr. Susan Love Research Foundation

Young Survival Coalition

Last Medical Review: 02/24/2014
Last Revised: 02/24/2014