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The BCERF program on the Cancer Risks of Environmental Chemicals in the Home and Workplace closed on March 31, 2010. No further updates will be made to this web site. Please go Cornell University’s eCommons web site to access BCERF’s archived research and educational materials (

The Sister Study

The Sister Study is a long-term study currently being undertaken to examine the interaction of environment and genes on breast cancer. The study, conducted by the National Institute of Health and Environmental Sciences, will follow 50,000 sisters of women who had breast cancer. The Ribbon newsletter (vol. 9, no. 4, Fall 2004) features the Sister Study.

Why Sisters?
Sisters share both genes and a common environment. As a study population, sisters of women who have had breast cancer offer unique opportunities for illuminating possible links between inherited and environmental risk factors. They also have about twice the usual risk of developing breast cancer, increasing the possibility of detecting interactions and small effects during the study. The sisters are expected to be a motivated group, willing to continue in the study and provide information over its entire ten-year length.

How is This Study Different?
The Sister Study is examining a cohort, or population selected for their common characteristics. (In this case the cohort is women whose sisters have had breast cancer.) A cohort study can also be called a prospective study. Because the population being studied has not yet developed the disease, their exposures are measured in the present, and their outcomes measured prospectively, over time. A key difference between this study and others done in the past is that the participants have not yet developed breast cancer. After diagnosis and/or treatment it is often more difficult to collect certain types of information because changes have already occurred in the body or in the individual's lifestyle (weight loss, diet, exercise, among others).

What Will Be Investigated?
The Sister Study focuses on the interaction of genes and environment for breast cancer risk. Current hypotheses about risk factors and gene-environment interactions for breast cancer risk will be tested, but the study design also opens the way to addressing new hypotheses as they emerge. It even leaves open the possibility of developing and validating new methods for measuring exposures - a notorious challenge in environmental health studies. Special effort will go into collecting information about environmental exposures both in the workplace and everyday life, including chemicals that may be hormonally active.

More Information
If you want to enroll or find out more about the Sister Study, visit the website: Take a moment to read through some of the Sister Stories on the website to see why some women are making the commitment to participate. You can read the article about the Sister Study in the Fall 2004 issue of The Ribbon. BCERF will continue to follow the study and provide updates.

Funded by:
National Institute of Environmental Health Sciences of the National Institutes of Health, Department of Health and Human Services.

Additional funding from:
The National Center on Minority Health and Health Disparities (NCMHD).

The American Cancer Society
The Susan G. Komen Breast Cancer Foundation
Sisters Network, Inc.
Y-ME National Breast Cancer Organization