A study published in the journal Cancer Epidemiology Biomarkers & Prevention, shows some women who have a genetic risk for developing breast cancer could benefit from taking oral contraceptives, a finding that contradicts earlier studies suggesting the pill could raise the risk.
The study included women who carry gene mutations in the BRCA1 or BRCA2 genes, a factor which substantially raises a woman's risk of developing breast and ovarian cancers over her lifetime. Women who don't have this mutation have a 12% lifetime risk of developing breast cancer, compared to a 65% chance in women who have BRCA1 mutations and 39% risk in women with BRCA2 mutations.
Researchers compared the use of oral contraceptives in 1,156 women who had been diagnosed with breast cancer before the age of 40, 47 of whom carried the BRCA1 mutation and 36 of whom carried the BRCA2 mutation, along with an additional 815 women in a control group. The study included women from Australia, as well as American and Canadian women.
After analyzing the data, the researchers concluded that taking birth control pills was associated with a reduced breast cancer risk for women who carried the BRCA1 mutation, but not in women who carried the BRCA2 mutation or who did not carry either mutation.
"We found that this lifetime risk was reduced to 10% to 20% for those women (with the BRCA1 mutation) who used oral contraceptives, much closer to that for women not carrying either mutation," said the study's lead author, Dr. John Hopper.
In the case of women with the BRCA2 mutation, oral contraceptive use did not appear to further increase the risk of developing breast cancer, the study noted.
Earlier studies have suggested that using oral contraceptives could actually raise a woman's risk of developing breast cancer, but Dr. Hopper theorized that changes to the hormone composition of the birth control pill in the years since those early studies could account for the change in risk.
"We are confident in our findings because we found the same results in Australia, Canada, and the United States and in women with and without a family history of breast cancer," he said.
But he added that more studies would be required to confirm that oral contraceptives could be used by women with the BRCA1 mutation to reduce their risk of developing breast cancer. More research is needed because only a small number of women in the study were carriers of the BRCA1 mutation.
"Currently, the only known way to reduce risk in mutation carriers is to surgically remove the breasts," Hopper said.
There are a number of factors that can indicate you may have a BRCA1 or BRCA2 mutation, including a history of breast cancer in two or more close relatives or in multiple generations of your family, a family member with both breast and ovarian cancer, and being of Ashkenazi (Eastern European) Jewish descent, whether or not you have a family history of breast cancer.
But just because breast cancer runs in your family doesn't mean you have this gene mutation. The only way to tell is through a blood test, though negative results are not a guarantee you won't get breast cancer.
If you do test positive for the BRCA1 or BRCA2 mutation, your doctor may recommend a number of strategies, including lifestyle changes such as limiting alcohol and losing weight, a more frequent surveillance schedule, medication, or preventative surgery.