News Release

Monday, October 5, 2009

Sister Study Exceeds Recruitment Goal: Now The Real Work Begins

The National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health, has many reasons to celebrate this October as it recognizes Breast Cancer Awareness Month. The NIEHS Sister Study began recruiting women for this landmark study during Breast Cancer Awareness month in October 2004 and this October has reached a milestone. It has recruited nearly 51,000 women from all walks of life, whose sisters had breast cancer, to participate in this long-term study that is focusing on uncovering environmental and genetic factors that influence breast cancer risk. These sisters and researchers have joined together in a long-term commitment to help prevent breast cancer.

"What an amazing group of women we have enrolled in this study. Every single one of them should be congratulated for their commitment to participating in research to help identify factors that lead to breast cancer," said Dale Sandler, Ph.D., chief of the Epidemiology Branch at NIEHS and principal investigator of the Sister Study. "We have exceeded our recruitment goal and I’m thrilled with the diversity of age, race, ethnicity and education represented in the cohort."

The women come from all 50 states as well as Puerto Rico, and include women with different ethnic, educational and employment backgrounds. Since the study began in 2004, 50,884 women have enrolled including 4,438 African-American women, 2,631 Hispanic women, and 1,160 women from other racial/ethnic groups. The study also includes 8,230 women aged 65 and over, and 7,212 with a high school degree or less. All of the women in the study have a sister who has been diagnosed with breast cancer. Researchers hope to uncover clues about causes of breast cancer and other diseases by comparing women who develop breast cancer or other conditions while in the study to those who remain disease-free.

"We owe a debt of gratitude to our participant volunteers who worked so hard to recruit women into the study and to our partner organizations that lent us their support," added Lisa DeRoo, Ph.D., lead investigator of the study. These organizations included the American Cancer Society, the Susan G. Komen for the Cure, the Sisters Network, the Intercultural Cancer Council, the Love/Avon Army of Women, the Breast Cancer Network of Strength, and many more local and national groups interested in breast cancer and women’s health.

Sandler points out that sustaining the same level of enthusiasm as the project moves forward is going to be the next challenge. "What we need now is for everyone to realize this is a 10-year study and that the work is really just beginning," Sandler said. The participants are asked to complete a yearly one-page update by mail, e-mail or phone. They are also asked to share more detailed information about changes in their health, jobs, and lifestyle every two or three years.

"Improvements in breast cancer survival depend on research participation so that we can learn why breast cancer begins and what controls cancer behavior," said Lisa Carey, M.D., medical director of the University of North Carolina Breast Center. "The Sister Study will need its participants to stay involved and to respond to inquiries about their health and experiences, especially if they are diagnosed with breast cancer."

Sandler adds, "Just like women everywhere, some women who joined the Sister Study will, unfortunately, be diagnosed with breast cancer or other conditions while they are part of the study. It is by comparing those who develop breast cancer to those who do not that we will be able to learn what might lead to breast cancer."

The volunteers in the Sister Study are at increased risk because they already have a sister who has had breast cancer. So far, approximately 900 participants have reported getting breast cancer since the study began.

The study collects additional information about their diagnosis and treatment from those sisters and their doctors. Such details are critical components of the study that will help determine the role that factors, such as occupational and environmental exposures, lifestyle, diet, stress, and genes might play in treatment outcomes and disease risks, and allow researchers to identify risk factors for specific types of breast cancer.

Participants, such as Jean Peelan in Florida, who has been participating in the study since its 2004 inception, recognize the value of the study and plan to stay involved."Continuing to participate in the Sister Study has been such an honor. I feel good that I am contributing to this incredible research, making such a difference, so that my six granddaughters may not have to face breast cancer in their future."

The study has already reported some preliminary findings about how factors such as weight and perceived stress may influence health, and investigators are beginning to use the biological samples participants contributed to learn how some genetic factors may affect breast cancer risk. The researchers point out key results on gene-environment interactions may be just a few years away.

Under the direction of Clarice Weinberg, Ph.D., chief of the Biostatistics Branch at the NIEHS, the researchers are also using the Sister Study as a way to better understand early-onset breast cancer.

They hope to enroll about 1,600 families, where there was a sister who was under the age of 50 when they were diagnosed with breast cancer, to participate in an offshoot of the Sister Study called the "Two Sister Study." The sister with breast cancer and her parents will be invited to participate along with the sister who is already part of the Sister Study.

"With women's participation in research like the Sister Study and the Two Sister Study, we hope to be one step closer to providing better care to women with breast cancer and finding the causes of the disease," said Susan Love, M.D., president of the Dr. Susan Love Research Foundation.

"Recruiting more than 50,000 Sister Study participants in five years was a huge accomplishment for the NIEHS," said NIEHS Director Linda Birnbaum, Ph.D. "Over the years, w'’ve received substantial support from a sister NIH agency, the National Center on Minority Health and Health Disparities, whose support enabled our researchers to develop unique strategies to recruit a diverse cohort. We appreciate the value that they and our many community partners and participants place on the promise of this research, and look forward to providing more insight into how to prevent breast cancer and other diseases that are influenced by the environment."

National Breast Cancer Awareness Month is dedicated to increasing awareness of the importance of early breast cancer detection. To learn more about the Sister Study and the Two Sister Study, visit, (for Spanish, visit

The NIEHS supports research to understand the effects of the environment on human health and is part of NIH. For more information on environmental health topics, visit our Web site at

About the National Institutes of Health (NIH): 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. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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