No link found between OCs and breast cancer

Be sure to include the following research finding in your counseling on oral contraceptives (OCs): Women who have taken the Pill at some point in their lives are no more likely to develop breast cancer between the ages of 35 and 64 than are other women the same age.1

That conclusion, derived from a large, population-based case-control study conducted at five U.S. metropolitan centers, should be very reassuring to women, says Kathy Helzlsouer, MD, MHS, professor of epidemiology at the Baltimore-based Johns Hopkins University’s Bloomberg School of Public Health and co-author of a commentary accompanying the research.2

Breast cancer is the most common cancer among women, other than skin cancer, according to the Atlanta-based American Cancer Society (ACS). It is the second-leading cause of cancer deaths in women after lung cancer. About 192,200 women in the United States will be found to have invasive breast cancer in 2001; about 39,600 women will die from the disease, according to the ACS.

About 80% of U.S. women born since 1945 have used oral contraceptives,3 and more than 10 million women between the ages of 15 and 44 years currently use them,4 states Polly Marchbanks, PhD, epidemiologist in the Division of Reproductive Health at the Atlanta-based Centers for Disease Control and Prevention.

"Given the serious nature of breast cancer and the high prevalence of oral contraceptive use, the results of this study are good news," states Marchbanks, who served as lead author of the analysis.

Examine the data

Researchers undertook the study to resolve the long-standing concern of whether former oral contraceptive use during the reproductive years would increase breast cancer risk later in life when the incidence of breast cancer is higher, explains Marchbanks.

Scientists have not been able to resolve this issue earlier because of calendar time. Since oral contraceptives were first marketed in 1960, only recently has the first generation of U.S. women who took the Pill early in their reproductive years reached the older ages of greatest breast cancer risk, she states.

The findings were compiled from the Bethesda, MD-based National Institute of Child Health and Human Development Women’s Contraceptive and Reproductive Experiences Study. Researchers interviewed more than 9,200 white and black women between the ages of 35 and 64 living in Atlanta, Detroit, Philadelphia, Los Angeles, and Seattle. About half of the study participants recently had been diagnosed with breast cancer, while the other half did not have a diagnosis of 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 issues.

When researchers analyzed 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), little evidence was revealed that the Pill increases breast cancer risk. Results generally were similar across age and racial groups. In addition, pill use among women with a family history of breast cancer was not associated with a significantly increased breast cancer risk.

While the study showed that women 35 to 64 years old currently using oral contraceptives were not at significantly increased breast cancer risk, results among older women may not be definitive, says Marchbanks. Why? Because only a small number of women 45-64 years old currently used the Pill during the period when the study participants were interviewed (1994-1998), she explains.

A 1996 comprehensive review and re-analysis of 54 studies of breast cancer found that women are not at increased risk for the disease after more than 10 years after stopping the Pill.5 However, that analysis indicated a slightly increased risk of breast cancer in women who were current or recent users of oral contraceptives. The new study was designed to lay any questions to rest about OC/breast cancer risks.

Oral contraceptives offer several health benefits outside of pregnancy protection, notes Andrew Kaunitz, MD, professor and assistant chair in the obstetrics and gynecology department at the University of Florida Health Science Center in Jacksonville. However, many women have wondered whether the advantages of Pill use would offset the potential risk of increased breast cancer risk. News of the study’s findings lets women know that regardless of age, formulation type, duration of use or family history, the Pill will not increase their current or future breast cancer risk, says Kaunitz.

References

1. Marchbanks PA, McDonald JA, Wilson HG, et al. Oral contraceptives and the risk of breast cancer. N Engl J Med 2002; 346:2,025-2,032.

2. Davidson NE, Helzlsouer KJ. Good news about oral contraceptives. N Engl J Med 2002; 346:2,078-2,079.

3. Blackburn RD, Cunkelman JA, Zlidar VM. Oral contraceptives: An update. Population Reports Spring 2000; Series A (No.9):5.

4. Abma JC, Chandra A, Mosher WD, et al. Fertility, family planning, and women’s health: New data from the 1995 National Survey of Family Growth. Vital Health Stat 1997; Series 23, Number 19.

5. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: Collaborative re-analysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996; 347:1,713-1,727.