Past Use of Birth Control Pills May Poses Additional Breast Cancer Risk for Women with BRCA1 Gene Mutations (dateline March 15, 2003)
Though the link between oral contraceptives and breast cancer risk has been debated over the years, recent studies have shown that women who take the pill today are typically not at a higher risk of breast cancer, compared to those who do not take the pill. However, a newly published study found that women who have a certain genetic mutation called BRCA1 might, in fact, be more likely to develop breast cancer, if they used oral contraceptives before 1975, when greater amounts of hormones were used in the pills. The findings do not apply to women who have taken the pill after 1975, since modern birth control pills contain fewer hormones, though women with BRCA1 gene mutations should exercise caution when considering oral contraception.
BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) are two genes that, when functioning normally, help repair damage to DNAa process that also prevents tumor development. In 1994, researchers discovered that women who carry mutations of BRCA1 or BRCA2 are at higher risk of developing both breast and ovarian cancer than women who do not have these genetic mutations. Mutations of these genes are uncommon. Women with BRCA1 mutations account for approximately 5% of all breast cancer cases.
To study the association between oral contraceptives and breast cancer risk, Steven A. Narod, MD of the Centre for Research on Womens Health in Toronto, Canada, and colleagues studied 2,600 women from 52 health centers in 11 countries. Approximately half of the women had taken birth control pills in the past, while the other half had not.
The results showed that women with BRCA1 gene mutations who used birth control pills had an even higher risk of developing breast cancer compared to women with BRCA1 gene mutations who did not use birth control pills. Specifically, women with BRCA1 gene mutations who used oral contraceptives before 1975, used them for longer than five years, or used them before age 30 were more likely to face an increased risk of early-onset breast cancer due to the pills. Oral contraceptives did not affect breast cancer risk in women with BRCA2 gene mutations.
The findings suggest that women with BRCA1 gene mutations who used birth control pills prior to 1975 should be aware of a possible increased risk for breast cancer, over and above the risk that the BRCA gene mutation poses. Birth control pills made after 1975 did not pose a risk. However, the American Cancer Society suggests that women with BRCA1 gene mutations approach the use of oral contraceptives with caution and discuss the issue with their physicians. Because birth control pills have been shown to decrease the risk of ovarian cancer, which also occurs more frequently in women with BRCA gene mutations, the true benefits and risks of the pill for BRCA1-affected women is unclear and needs further research.
Recent studies have shown that modern birth control pills do not typically increase breast cancer risk. For example, a study of over 9,000 women, published in the June 27, 2002 issue of the New England Journal of Medicine, found that oral contraception does not increase breast cancer risk in women who have taken birth control pills in the past. The study involved analyzing the health of 4,575 women between the ages of 35 and 64 who had breast cancer and comparing them with 4,682 women of the same age without breast cancer. Approximately four out of five women in both groups had used oral contraceptives at some point in their lives.
The belief that oral contraceptives cause breast cancer stems from the fact that birth control pills contain hormones, including estrogen and/or progesterone (estrogen has been linked with a higher risk of breast cancer in women who take hormone replacement therapy for five years or more). Birth control pills manufactured prior to 1975 contained significantly higher amount of these hormones, but todays versions of the pills have very low levels of hormones.
Over 45 million women have used oral contraceptives at some point in their lives, and an estimated 10 million women between the ages of 15 and 44 take them today.