Birth Control Shots tied to Breast Cancer risk

By RITA RUBIN | MSNBC | APRIL 9 2012

Recent use of the injectable contraceptive Depo-Provera for at least a year was associated with a doubling of young women’s breast cancer risk, a new study has found.

However, users’ breast cancer risk dropped to that of non-users within several months of stopping Depo-Provera injections, researchers report in the journal Cancer Research.

Depo-Provera, injected every three months, was approved as a contraceptive in the United States 20 years ago. Convenient, highly effective and relatively inexpensive, Depo-Provera is used by about 1.2 million U.S. women, or 3.2 percent of those who practice contraception, according to the latest data from the Guttmacher Institute, a research and education organization that focuses on reproductive health.

The injectable birth control method is the only contraceptive in the United States that contains the same progestin, or synthetic hormone, as Prempro, the postmenopausal hormone therapy pill. A landmark government study called the Women’s Health Initiative found that Prempro, a combination of estrogen and progestin, increased women’s breast cancer risk by 24 percent, while Premarin, which contains only estrogen, did not increase risk.

‘’Our hypothesis going into this study was that we did expect to see an increased risk of breast cancer associated with Depo-Provera,” says Dr. Christopher Li, a breast cancer epidemiologist at the Fred Hutchinson Cancer Research Center and lead author of the new study.

Data on the relationship between Depo-Provera and breast cancer risk are limited, the researchers write. Li and his coauthors say theirs is the first large-scale U.S. study specifically designed to evaluate the relationship. Results from similar studies conducted in other countries have been mixed, they write.

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