Some pill users at more risk
Questions about the link between breast cancer and birth control pills have lingered for years.
To date, research has shown only a slight increase in breast cancer risk among younger women who take oral contraceptives. And two years ago, a study indicated that only women who took pills made before 1975, when the estrogen content of pills was much higher, are at increased risk.
A study released last week, however, offers the first strong evidence that a subset of women are at increased risk for breast cancer if they take even today’s lower-estrogen pills.
The report, in the Journal of the National Cancer Institute, found that women who carry a BRCA1 gene mutation and use oral contraceptives for five or more years have a 33% increased risk of early-onset breast cancer, compared with those who have the mutation and never used the pill. The risk was greatest for women younger than 30. Breast cancer that occurs earlier in a woman’s life is associated with more severe disease.
Researchers did not find a link between breast cancer and pill use for those with BRCA2 gene mutations, although they called for more investigation.
About 1 million U.S. women carry the BRCA1 or BRCA2 gene mutations. Women with the mutations have a 50% to 80% lifetime risk of having breast cancer.
The research further underscores the benefits of knowing whether one carries the BRCA gene mutations. “The gene was found in 1994, and we’ve been offering testing since 1996. But most carriers in the United States don’t know [their status] yet,” said the study’s lead investigator, Dr. Steven A. Narod of the Sunnybrook and Women’s College Health Sciences Centre and the University of Toronto.
The question of whether to take the pill is complicated for those with mutated BRCA because women with either of the gene mutations also have a 60% to 85% chance of developing ovarian cancer by age 70. Studies show that oral contraceptive use may reduce the risk of ovarian cancer by 30% to 50%.
The new study suggests that taking the pill after age 30 is not likely to increase the risk of breast cancer among BRCA1 users with the mutated gene, and it can be used safely to reduce ovarian cancer risk, Narod said. Younger women may be at higher risk for breast cancer when taking the pill because their breast tissue is still developing and could be more vulnerable to the estrogen in the pill, he said. The data analyzed use of the pill among 1,311 women with mutated BRCA who had breast cancer and 1,311 who did not.
