Media splashy headlines can distort. There was a recently published study from Denmark showing an increase risk for breast cancer in women with progesterone IUDs. The increase? 1 in 204 to 1.4 in 204 patients. The splashy headline? 40% increased risk! PLEASE SEE HOW THE ABSOLUTE RISK IS LOW, and this is the SAME as the increased risk of breast cancer shown in most birth control pills. The rate of breast cancer is 12% (1 in 8). For those with IUDs, the “40% increase” was a super tiny increase in absolute numbers. (From 1 to 1.4 for every 200+ people. This difference of 0.4/204 women = .019% increase, but that is not a splashy headline.)
Study:
- 78,595 women in Denmark
- ages 15-49
- Had progesterone IUDs (like Mirena, Litella, Kyleena- NOT a copper IUD which has no hormone)
- “Those who used progesterone IUDs had a 40% higher chance of developing breast cancer.”
The NY Times did a great article on this, and they quoted a Dr. from Mayo Clinic stating, “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.”
In one of my doctor chat groups, doctors brought up other great points:
- This is an association study, not causation
- The absolute risk is very very low.
- These IUDs have other benefits- reduce endometrial and ovarian cancer, prevent blood transfusions for those with super heavy bleeding with periods
- There are no reversible contraceptives as effective. Pregnancy is always more risky than an IUD
- Other confounding factors- did the IUD users have fewer pregnancies (pregnancy and breastfeeding are protective against breast cancer)
So for those reading this, particularly in this time of super deceptive media and headlines, please use a trusted source (like my blog I am hoping) to interpret the information. At first glance, the large number of people studied makes this study seem valid. The slight increase is real. But you need to understand the context, and the headline of “40% increase” is just terribly deceptive.
The study was published in JAMA October 2024, “Breast Cancer in Users of Levonorgesterel-Releasing Intrauterine Systems.” See the original article HERE.