Breast Cancer Risk Factors: Lesbian & Heterosexual Women

Institution: Lyon-Martin Women's Health Services
Investigator(s): Stephanie Roberts, M.D. - Suzanne Dibble, D.N.Sc., RN -
Award Cycle: 1997 (Cycle III) Grant #: 3AB-2400 Award: $23,991
Award Type: CRC Pilot Award
Research Priorities
Detection, Prognosis and Treatment>Imaging, Biomarkers, and Molecular Pathology: improving detection and diagnosis

This is a collaboration with: 3AB-2401 -

Initial Award Abstract (1997)
In 1993, Dr. Suzanne Haynes, a government scientist, reported that lesbians might have a greater chance of getting breast cancer (1 in 3) than women in general (1 in 8). This was based upon some evidence that lesbians may choose a lifestyle that has been connected with the development of breast cancer (not having any children, not breastfeeding, smoking, drinking). However, there has not been a good scientific study that looks at the differences in these and other breast cancer risk factors between lesbian and heterosexual women.

We plan to look for possible differences by reviewing the medical records of about 1700 women over the age of 35. These records are from visits during 1995 and 1996 to Lyon-Martin Women’s Health Services (LMWHS), a clinic in San Francisco with special outreach to lesbians. Over half of the patients (52%) are lesbian, 40% are heterosexual, and 8% are bisexual. The facts in the records will be kept secret by using a code number rather than a name on all forms. Information from the records will be put into a computer program and the risk factors for breast cancer will be compared between lesbian and heterosexual women.

If we find that there is a difference in risk factors, then doctors and nurses must learn about these differences. Then, they will be better able to provide information to lesbians about their risk of developing breast cancer and other facts that they need to take good care of themselves. Lesbians must also learn about these differences so that they go to a doctor or nurse if they find any lumps or changes in their breasts. The findings from this small study will be checked and expanded with a much larger group of women. Studies will also need to be done to find the best ways to reach lesbians for breast cancer screening.

Final Report (1998)
Lesbians have been reported to have a much greater chance of getting breast cancer than heterosexual women; yet no studies have been reported comparing the distribution of risk factors for the development of breast cancer between these two groups of women. Therefore, the purpose of this study was to compare the differences in the distribution of risk factors for developing breast cancer between lesbian and heterosexual women. The sample included medical records from women, age 35 or older, seen at Lyon-Martin Women's Health Services in San Francisco. The typical participant (n=1019) was 42.9 years old, white (70%), heterosexual (57.6%), and employed (49.9%). Most were without health insurance and 99% were poor (<15,780 annual income).

There were no significant differences between the lesbian and heterosexual women in family history of breast cancer, current alcohol usage or history of alcohol problems, age at menarche and menopause, or use of hormone replacement therapy. The lesbians reported more breast biopsies, less use of birth control pills, higher body mass index, fewer pregnancies and fewer biological children. These results would suggest that lesbians are at higher risk for the development of breast cancer. Future studies should sample women of different ages, economic groups, and geographic regions to further explore these differences. If these differences are replicated in a larger study of California women, then the next step will be to inform both lesbians and their health care providers of the potential risks for the development of breast cancer. Studies will also be needed to find the best ways to reach lesbians for breast cancer screening.