Breast cancer susceptibility gene-1 (BRCA1) and breast cancer susceptibility gene-2 (BRCA2) mutation carriers have high risks of developing breast cancer and ovarian cancer at a relatively young age. It is estimated that the cumulative risk to age 80 in female BRCA1 mutation carriers is over 80% for breast cancer and over 50% for ovarian cancer. Use of oral contraceptives (birth control pills) significantly reduces the risk of ovarian cancer among BRCA mutation carriers. However, the protection that birth control pills confer against ovarian cancer might come at the cost of an increase in breast cancer risk.
Generally speaking, oral contraceptive use is weakly associated with breast cancer risk. However, the risk is greater for women who start oral contraceptives at a very young age. Now a new study has reported that women with a BRCA1 mutation should probably avoid taking birth control pills before age 25.
Latest research finds pill use at young age increases BRCA1 breast cancer risk
The case-control study referenced at the beginning of this news story was designed to investigate the relationship between age of oral contraceptive use and breast cancer among BRCA1 mutation carriers. The study included 2,492 matched pairs of women with harmful BRCA1 mutations. BRCA1 carriers who had been diagnosed with breast cancer were matched with unaffected carriers based on year of birth and country of residence. A questionnaire was used to collect detailed information about birth control use. The goal was to determine the association between birth control pill use and breast cancer by age at first use and by age at diagnosis.
Birth control pill use was found to be significantly associated with an increased risk of breast cancer among BRCA1 mutation carriers who began taking the pill before age 20 and possibly those who began between ages 20 and 25 as well. This effect was limited to breast cancers diagnosed before age 40. Each additional year of birth control pill use increased the risk of early-onset breast cancer by 11% when initiated prior to age 20. However, no increase was observed among women diagnosed after age 39. The authors conclude that birth control use before age 25 heightens the risk of early-onset breast cancer conferred by harmful BRCA1 mutations. This risk increases with duration of use. Caution should be taken when advising women with a BRCA1 mutation to take an oral contraceptive prior to age 25, according to the authors.