A recent study suggests a link between high-dose combined oral contraceptives that were discontinued in most countries years ago and an increased risk of breast cancer among women with a strong family history of the disease.
Women in the United States who used oral contraceptives before 1975 and whose mothers or sisters had breast cancer showed a substantially increased risk of developing the cancer, according to scientists at the Mayo Clinic and University of Minnesota. Because of the study's limitations, pill use after 1975 among women with a strong family history of breast cancer could not be adequately evaluated. The scientists concluded further research was needed to assess this risk. Their findings were published in the October 11, 2000 issue of the Journal of the American Medical Association.1
High-dose pills have not been available in most countries for more than a decade. If still available, women should use low-dose pills instead, especially if they have a family history of breast cancer. No studies suggest that today's low-dose combined oral contraceptives pose a cancer risk in any population.
Prior to 1975, oral contraceptives that combined an estrogen with a progestin contained relatively high doses of estrogen. In many countries, use of these high-dose pills was discontinued as lower-dose formulations were developed, but high-dose pills continued to be used in some locations. The high-dose pills that were used by women in the study contained up to 150 µg of the estrogen mestranol. Most pills used since 1975 contain 50 µg or less of a different estrogen, ethinyl estradiol.
The study tracked 394 sisters and daughters, and 3,002 granddaughters and nieces, of women who were diagnosed with breast cancer between 1944 and 1952. It also included 2,754 women who married into the families of breast cancer patients. Women in the study were interviewed between 1991 and 1996.
The sisters and daughters of breast cancer patients who took high-dose pills prior to 1975 and who had three blood relatives with breast cancer faced nearly a five-fold increased risk of developing the cancer, compared with women who did not use the pills. The risk was more than 11 times greater for high-dose users with five blood relatives with breast cancer. The results are similar to previous findings that link women with a family history of breast cancer to a higher risk of breast cancer from pill use.2
The women found at most risk of breast cancer were sisters or daughters of women with breast cancer. Granddaughters, nieces and women related by marriage to women who developed breast cancer were not at a significantly greater risk even if they had used higher dose pills prior to 1975. In other words, a family history of breast cancer alone does not necessarily mean increased risk. However, there is a possibility that rates of breast cancer among granddaughters may have been lower because these women were at a younger age when studied, and breast cancer typically develops later in life.
Protective benefits
Other research has shown that oral contraceptives provide protection against ovarian cancer. Ovarian cancer is harder to detect in the early stages than breast cancer and is often fatal. The protective effect against ovarian cancer may last as long as 15 years after stopping pill use. Women who have used combined oral contraceptives for four years are 30 percent less likely to develop ovarian cancer than women who have never used the pill; women using pills five to 11 years are 60 percent less likely; and for 12 or more years of use they are 80 percent less likely.3
Because of protective effects, some women with a family history of ovarian cancer take the pills to reduce their risk of ovarian cancer. There is also evidence that the pill protects against cancer of the uterine lining (endometrial cancer).4 Pill use also has other health benefits. Pills protect against ectopic pregnancy and may protect against fragile bones (osteoporosis) and endometriosis.5
Some women, however, should not use combined oral contraceptives. Some examples include women who are heavy smokers and are over 35 years old; women who have high blood pressure; women who have a history of deep-vein thrombosis, heart attack or stroke; or women over 35 years old who experience severe headaches with focal neurological symptoms (such as visual disturbances). Moreover, pill use is not recommended for women who have certain preexisting conditions such as current breast cancer, benign liver tumors, liver cancer or active viral hepatitis.6
-- Ellen Devlin
References
- Grabrick DM, Hartmann LC, Cerhan JR, et al. Risk of breast cancer with oral contraceptive use in women with a family history of breast cancer. JAMA 2000; 284(14):1791-98.
- Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996;347(9017);1713-27; Rosenberg L, Palmer JR, Rao RS, et al. Case-control study of oral contraceptive use and risk of breast cancer. Am J Epidemiol 1996;143(1):25-37.
- Petitti DB, Porterfield D. Worldwide variations in the lifetime probability of reproductive cancer in women: implications of best-case, worst-case and likely-case assumptions about the effect of oral contraceptive use. Contraception 1992;45(2):93-104; Narod SA, Risch H, Moslehi R, et al. Oral contraceptives and the risk of hereditary ovarian cancer, N Engl J Med 1998;339(7):424-28.
- Harlap S, Kost K, Forrest JD. Preventing Pregnancy, Protecting Health: a New Look at Birth Control Choices in the United States. New York and Washington: The Alan Guttmacher Institute, 1991; Grimes DA, Economy KE. Primary prevention of gynecologic cancers. Am J Obstet Gynecol 1995;172(1):227-35.
- DeCherney A. Bone-sparing properties of oral contraceptives. Am J Obstet Gynecol 1996;174(1):15-20; Fortney JA, Feldblum PJ, Talmage RV, et al. Bone mineral density and history of oral contraceptive use. J Reprod Med 1994;39(2):105-9; Guillebaud J. Contraception Today: A Pocket Book for General Practitioners, Third Edition. London: Martin Dunitz, 1997; Speroff L, Darney P. A Clinical Guide for Contraception. Baltimore: Williams and Williams, 1996.
- World Health Organization. Improving Access to Quality Care in Family Planning, Medical Eligibility Criteria for Contraceptive Use. Geneva: World Health Organization, 1996.
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