WASHINGTON, Oct 18, 2004 (United Press International via COMTEX) -- U.S. scientists began enlisting volunteers Monday for a study of 50,000 sisters of women diagnosed with breast cancer.

Known as the Sister Study, it will investigate environmental and genetic causes of breast cancer. The Sister Study is the largest study of its kind to look at breast cancer risk factors.

Women of all backgrounds and ethnic groups are eligible for the study if they are between the ages of 35 and 74; live in the United States; have never had breast cancer themselves; and have a sister living or deceased who has had breast cancer.

To recruit a diverse group of volunteers and to ensure the results benefit all women, researchers are especially encouraging African-American, Latina, American Indian and Asian women, as well as women 60 and older, to join the Sister Study.

The study is being conducted by the National Institute of Environmental Health Sciences, part of the National Institutes of Health.

The landmark study will stay in touch with the volunteers for 10 years and compare those who develop breast cancer with the majority who do not. The Sister Study will take the most detailed look ever at how women's genes, and things women come in contact with at home, at work, and in the community may influence breast cancer risk.

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