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Study links early birth control pills to breast cancer risk for some women
ATLANTA, Georgia (CNN) -- A new study suggests women with a strong family history of breast cancer may have an increased risk of getting the disease themselves if they took birth control pills before 1975.
"It's only the formulations that were marketed initially in this country that were very high in terms of estrogen and progestin that seem to be influencing the risk," said Mayo Clinic epidemiologist Thomas Sellers.
Sellers and colleagues studied thousands of women from 426 families with a history of breast cancer.
Their study, published in this week's Journal of the American Medicial Association, is thought to be the first to evaluate the link between pill use and an inherited risk for breast cancer.
For women who took birth control pills before 1975, the researchers found a three-fold increase in breast cancer among daughters and sisters of women with the disease.
And there was an 11-fold increase among pill users with an excessive family history -- that is, five or more close relatives with breast or ovarian cancer.
"What this study tells them is if they were exposed to oral contraceptives marketed before 1975, if they haven't been getting their screening mammograms, they have extra incentive to do that," Sellers said.
Birth control pills are one of the leading forms of contraception, second only to sterilization. Some 100 million women use the pill worldwide, according to the journal Population Reports.
Although some studies have found a weak relationship between breast cancer and women who take oral contraceptives, the Mayo study did not echo those results.
"When we look at our study population who was exposed to oral contraceptives marketed after 1975, we don't see any suggestion of increased risk," Sellers said.
Hormone dosages in the pill were lowered after 1975.
While that could be reassuring to women currently on the pill, said obstetrician/gynecologist Michael Randell, "we're going to have to look at this because women are taking birth control pills much longer."
The Mayo researchers agree more research is needed to evaluate any link between use of current birth control pills and breast cancer in families at risk for the disease.
But doctors say all women should be vigilant about breast cancer detection since the majority of those who get it have no family history of the disease.
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Planned Parenthood Federation of America
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