CHICAGO — Birth control pills taken before 1975 may carry a higher risk of breast cancer for close relatives of victims of the disease, a study said Tuesday.
Concerns that women who take oral contraceptives may be raising their risk of contracting breast cancer have largely been defused in recent years, based on previous studies.
But a Mayo clinic study of 426 Minnesota families published in this week's issue of the Journal of the American Medical Association showed certain at-risk women who took the pill prior to 1975 may have reason to be concerned.
Still, the multi-generation study may hold positive news for women who have taken newer formulations of the pill produced since 1975, which contain smaller dosages of the hormones that prevent pregnancy and have so far presented no increased risk of contracting breast cancer.
Women have long known that oral contraceptives can protect them from ovarian cancer and some who have a family history of cancer have been advised to take the pill. Family history is a known risk factor for breast cancer, particularly among women carrying mutations of the BRCA1 and BRCA2 genes.
The latest study led by Dawn Grabrick of the Mayo Clinic Cancer Center in Rochester, Minnesota, which followed women for up to 50 years, found that in families with three breast cancer victims diagnosed between 1944 and 1952, their sisters and daughters who took oral contraceptives prior to 1975 were at three times the risk of contracting the disease. Those with five family members with the disease raised their risk 11-fold if they took the pill.
But there was no increased risk of breast cancer among birth control pill-users among the 3,002 granddaughters or nieces of the cancer victims, or among the women marrying into the families.
The disappearance of cancer risk among the next generation may be due to their relatively young age, given that breast cancer often shows up later in life, wrote Wylie Burke of the University of Washington, Seattle, in an editorial accompanying the study.
Or it could have more to do with newer forms of the pill that contain much lower doses of estrogen that some blame for heightened breast cancer risk, he wrote.