Women between the ages of 35 and 64 who took oral contraceptives at some point in their lives are no more likely to develop breast cancer than are other women the same age, according to findings from the National Institute of Child Health and Human Development (NICHD) Women's Contraceptive and Reproductive Experiences Study (Women's CARE).
The study, published in the June 27 issue of the New England Journal of Medicine, was conducted in order to determine whether current or former contraceptive use during the reproductive years increases breast cancer risk. The women studied are members of the first generation of American women to use oral contraceptives.
"Women between the ages of 35 and 64 are more likely to develop breast cancer than are younger women," said Duane Alexander, M.D., Director of the NICHD. "It is very reassuring that the NICHD Women's CARE study found no increase in breast cancer risk among past or present oral contraceptive users in this age group."
In the study, the researchers interviewed women who had recently been diagnosed with breast cancer about their previous use of oral contraceptives. The responses of these women were compared to the responses of a similar group of women who did not have breast cancer. The researchers interviewed more than 9,200 white and black women between the ages of 35 and 64 years living in Atlanta, Detroit, Philadelphia, Los Angeles, and Seattle. Roughly half of the study participants had breast cancer, while the other half did not have a diagnosis of breast cancer but lived in the same geographic locations as the participating women who did have breast cancer. The women were interviewed in person and asked a series of questions about their use of oral contraceptives and other hormones, as well as their reproductive, health, and family histories.
Compared to women who had never used oral contraceptives, women who had used any type of oral contraceptive did not have a greater risk of developing breast cancer. Furthermore, according to the study's authors, "Examination of multiple aspects of oral contraceptive exposure (ever, current, or former use, duration of use, age at first use, time since last use, and use by estrogen dose) revealed little evidence that oral contraceptives increase breast cancer risk." Results were similar for women aged 35 to 44 and 45 to 64 years, and did not vary by race. In contrast to previous studies, the current study also found that oral contraceptive use among women with a family history of breast cancer was not associated with an increased breast cancer risk.
Approximately 80 percent of U.S. women born since 1945 have used oral contraceptives. There has been some concern in the past about the possible effect of oral contraceptive use on breast cancer risk. In fact, a 1996 formal review of 54 smaller studies conducted over the past 25 years found a slightly increased risk of breast cancer in women who were current or recent users of oral contraceptives. Other previous studies did not find an increased risk of breast cancer among oral contraceptive users.
"Large numbers of women who took oral contraceptives during their reproductive years are now reaching the ages of greatest breast cancer risk," said Robert Spirtas, Dr.P.H., Chief of NICHD's Contraception and Reproductive Health Branch and one of the authors of the study. "We conducted this study to resolve the long-standing concern that oral contraceptive use might be associated with an increased risk of breast cancer in later life. Our study provides scientific evidence that there is no such association."
According to Polly A Marchbanks, Ph.D., and the other authors of the study, "Current and former oral contraceptive use among women 35 to 64 years was not associated with significantly increased breast cancer risk."
The research centers participating in the NICHD Women's CARE Study were Emory University in Atlanta, Fred Hutchinson Cancer Research Center in Seattle, Karmanos Cancer Institute at Wayne State University in Detroit, University of Pennsylvania in Philadelphia, and University of Southern California in Los Angeles. The Centers for Disease Control and Prevention (CDC) was the Data Coordinating Center.
In addition to funding by the NICHD, the National Cancer Institute (NCI) also provided financial support for the study. The CDC contributed computer support and staffing.
The NICHD is part of the National Institutes of Health, the biomedical research arm of the Federal government. The Institute sponsors research on development before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. NICHD publications, as well as information about the Institute, are available from the NICHD website, http://www.nichd.nih.gov, or from the NICHD Information Resource Center, 1-800-370-2943;E-mail NICHDInformationResourceCenter@mail.nih.gov.