Women who carry a gene mutation known as BRCA1 may be at a modestly higher risk of early-onset breast cancer if they have used birth control pills for five years or more, according to a study published in the Journal of the National Cancer Institute.
Women with the BRCA1 and BRCA2 mutations have a 50 to 80 per cent risk of developing breast cancer. However, BRCA1 carriers who have used oral contraceptives for five years or more have a 33 per cent increased risk of early-onset breast cancer, compared with carriers who have never used birth control pills, says Dr. Steven Narod, lead author of the study and professor of public health sciences at U of T.
Carriers are also at elevated risk if they used birth control pills before age 30, were diagnosed with breast cancer before age 40 or used the pill before 1975, according to Narod and his colleagues. “I suggest that women with BRCA1 mutations not use the pill before age 25,” says Narod, who holds the chair in breast cancer research from the Canadian Breast Cancer Foundation (Ontario chapter) at Sunnybrook and Women’s College Health Sciences Centre. “From ages 25 to 30, women may use the pill for birth control reasons as required. However, this is a complicated issue, and I recommend that women get individual assessments.”
In Canada, approximately one in 200 women carries one of these mutations.