Comparing breast cancer risk between lesbians and their heterosexual sisters



      The purpose of this study was to explore the similarities and differences between lesbians and their heterosexual sisters in the established risks for developing breast cancer.


      The design for this study was a matched (lesbian with heterosexual sister) cross-sectional, mail-back, anonymous survey. We distributed the surveys throughout the state of California to English-speaking women who identified themselves as lesbians, age 40 and older, and their sisters. Using the modified Gail Breast Cancer Risk model as well as other well-established factors associated with the development of breast cancer, we compared the breast cancer risk potential for 324 sister pairs (N = 648). Data were analyzed using paired t-tests, analysis of covariance (ANCOVA), McNemar's χ2, or the Bowker statistic, as appropriate for the level of data.

      Main findings

      The lesbians had significantly higher 5-year (p < .0001) and lifetime (p = .001) risk for developing breast cancer. The reasons for lesbians' predicted rate of breast cancer were most likely their higher scores on all pregnancy-related variables and the relatively high number of breast biopsies they reported. The lesbians had used birth control pills less (p <. 0001), had significantly fewer pregnancies (p < .0001), children (p < .0001), abortions (p < .0001), and miscarriages (p < .0001) as well as significantly more breast biopsies (p = .02) than did their heterosexual sisters.


      A lesbian who comes out to her clinician is relying on the clinician to be informed and be open to discuss her life. When a lesbian has a lump or a suspicious mammogram, she needs her clinician to advocate for her within the health care system because she is at higher risk for having cancer than a heterosexual woman.
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      Dr. Suzanne Dibble is a Professor of Nursing at the Institute for Health and Aging and Co-Director of the Lesbian Health Research Center at the University of California, San Francisco.


      Stephanie Roberts, MD, formerly Medical Director at Lyon-Martin Women's Health Services in San Francisco, is currently in private practice in Walnut Creek, California.


      Brenda Nussey is a Programmer/Analyst in the Institute for Health and Aging who works on breast and cervical cancer research projects.