A new study adds to the evidence on hormonal contraceptives and breast cancer. But experts stressed the overall risk remains low.
A study published Wednesday found that women using contraceptive intrauterine devices that deliver a certain hormone are at increased risk of breast cancer, though risk of the disease in these women remained low overall.
The research looked at 78,595 women in Denmark between the ages of 15 to 49 years who used levonorgestrel IUDs, which in the United States are known by the brand names Mirena, Liletta, Kyleena and Skyla. Researchers compared them to 78,595 women who did not use the devices but otherwise had similar profiles. Those who used levonorgestrel IUDs had a 40 percent higher chance of developing breast cancer. For women in their 30s in the United States, that would take the risk of breast cancer from about 1 in 204 to about 1.4 in 204. It’s about the same increase in breast cancer risk that has been shown with oral contraceptive pills.
Even with that increased risk, breast cancer remains rare among women under 50, and extremely rare for women under 30.
Dr. Daniel Breitkopf, the chair of the department of obstetrics and gynecology at the Mayo Clinic in Rochester, Minn., said that when he discusses the risks of hormonal contraceptives, he makes this clear. “The way I talk to patients about that is, if I tell you I’m going to double your chances of winning the lottery, you’re not going to go out and buy a lottery ticket — because the chances of winning are still very, very low.”
And he stressed that for many patients at average risk of breast cancer, the benefits of the contraceptives often outweigh the risks.
Hormonal IUDs, which have become increasingly popular in recent years, prevent pregnancy in part by delivering small amounts of hormones inside the uterus. In Denmark, where the study took place, hormonal IUDs are the preferred form of contraception among women who have given birth, said Lina Morch, the head of the research team at the Danish Cancer Institute. Dr. Morch was the lead author of the new paper, which was published in JAMA.