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Recent DMPA use doubles breast cancer risk in study

Wednesday April 4, 2012
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Recent use of an injectable form of progestin-only birth control doubles the risk of breast cancer in young women, according to what researchers described as the first large-scale, U.S.-based study to evaluate the link.

Although the contraceptive, depo-medroxyprogesterone acetate, contains the same kind of progestin as the menopausal hormone-therapy regimen found by a Women’s Health Initiative clinical trial to increase breast cancer risk among postmenopausal women, few studies have evaluated the link between DMPA use and breast cancer risk in younger women, the researchers said.

"While DMPA is widely used by women throughout the world, there are limited data on the association between DMPA and breast cancer incidence," lead investigator Christopher I. Li, MD, PhD, of the Fred Hutchinson Cancer Research Center in Seattle, said in a news release. "Our study adds to the body of knowledge from international studies conducted in a diverse group of countries — Kenya, New Zealand, Thailand, Mexico and Costa Rica — which have shown that one of the risks associated with DMPA use may be an increased risk of breast cancer."

The researchers found that recent DMPA use (within five years) for 12 months or longer was associated with a 2.2-fold increased risk of invasive breast cancer. This risk appeared to be dispelled within months after contraceptive use was discontinued. The researchers also found that women who used the contraceptive for less than a year or who had stopped using it more than a year earlier did not have an increased risk of breast cancer.

"Although breast cancer is rare among young women and the elevated risk of breast cancer associated with DMPA appears to dissipate after discontinuation of use, our findings emphasize the importance of identifying the potential risks associated with specific forms of contraceptives given the number of available alternatives," the authors wrote in the April 15 issue of Cancer Research.

The study involved 1,028 Seattle-area women ages 20 to 44 who had been diagnosed with breast cancer and 919 age-matched controls who did not have a history of breast cancer. Of these, about 10% reported using DMPA, which is consistent with usage patterns nationwide, Li said. Use of the injectable contraceptive was about 5% higher among non-white women in the study.

"In the United States many women have numerous options for contraception, and so it is important to balance their risks and benefits when making contraceptive choices," Li said.

To download a PDF of the study, visit http://bit.ly/HihePn.

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