Use of the injectable contraceptive, Depo-Provera (depo-medroxyprogesterone acetate, or DMPA), may increase the likelihood that a young woman will develop invasive breast cancer, according to the first U.S. large-scale study to examine the issue. The study, which appears in the April 15th issue of Cancer Research, found that recent use of the progestin-only birth control method more than doubles the risk that a woman will develop breast cancer.
Depo-Provera provides protection against pregnancy for up to 14 weeks, but the shot must be received once every 12 weeks to remain fully protected. Recent figures from the Guttmacher Institute indicated that Depo-Provera is used by about 1.2 million U.S. women, or 3.2 percent of those who practice contraception.
According to a press release from the Fred Hutchinson Cancer Center, DMPA 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. A possible association between Depo-Provera and breast cancer in young women has never been studied, though research out of several countries has found a possible link between DMPA and the disease.
In order to add to the body of knowledge from international studies, researchers from the Fred Hutchinson Cancer Center compared data on 1,028 Seattle-area women ages 20 to 44 who had been diagnosed with breast cancer to 919 age-matched controls who did not have a history of breast cancer. About 10 percent of subjects in the study reported using DMPA.
The study found that 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. However, the risk lessened in the months after a woman stopped using Depo-Provera. Women who used DMPA 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 United States many women have numerous options for contraception, and so it is important to balance their risks and benefits when making contraceptive choices,” lead researcher Christopher I. Li, M.D., Ph.D., said.
“This study further confirms that some types of progestins are not healthy for the breast. For women who are at elevated risk to develop breast cancer based on family history, or even age, this type of contraception may not be a good choice for them,” Dr. Elizabeth Poynor, a gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital in New York City, told HealthDay News.