Long-acting intrauterine contraceptive device may raise breast cancer risk
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Key takeaways:
- Levonorgestrel-releasing intrauterine system users vs. nonusers had an increased risk for breast cancer.
- Breast cancer risk increased with years of levonorgestrel-releasing intrauterine system use.
Using a levonorgestrel-releasing intrauterine system device to prevent pregnancy increased risk for breast cancer among women living in Denmark aged 15 to 49 years, according to a research letter published in JAMA.
“Levonorgestrel-releasing intrauterine system use constitutes the preferred hormonal contraception among Danish premenopausal women older than 30 years,” Lina Steinrud Mørch, MSc, PhD, team leader in the department of cancer and medicine at The Danish Cancer Institute in Denmark, and colleagues wrote. “However, whether use of an levonorgestrel-releasing intrauterine system is associated with breast cancer risk remains unclear.”
Mørch and colleagues conducted a nationwide study using data from Danish registers from 78,595 first-time initiators (mean age, 38 years) of any levonorgestrel-releasing intrauterine system at doses of 52 mg, 19.5 mg and 13.5 mg from 2000 to 2019. Researchers matched women using the intrauterine system with women who were hormonal contraceptive nonusers and followed all participants until breast cancer diagnosis, other cancer diagnosis, pregnancy, postmenopausal hormone therapy initiation, emigration, death or December 2022.
During a mean follow-up of 6.8 years, 1,617 participants had a breast cancer diagnosis, of whom 720 were levonorgestrel-releasing intrauterine system users.
Levonorgestrel-releasing intrauterine system users had an increased risk for breast cancer compared with hormonal contraceptive nonusers (HR = 1.4; 95% CI, 1.2-1.5). Breast cancer risk increased along with years of use for women who used levonorgestrel-releasing intrauterine systems for 0 to 5 years (HR = 1.3; 95% CI, 1.1-1.5), more than 5 to 10 years (HR = 1.4; 95% CI, 1.1-1.7) and more than 10 to 15 years (HR = 1.8; 95% CI, 1.2-2.6).
Per 10,000 users, the increased breast cancer risk corresponding to years of use resulted in an excess of 14 breast cancer diagnoses for 0 to 5 years, 29 diagnoses for more than 5 to 10 years and 71 diagnoses for more than 10 to 15 years.
“Although the absolute breast cancer risk is low in young women, this study found an excess risk of 14 per 10,000 females. The risk did not increase with duration of [levonorgestrel-releasing intrauterine system] use,” the researchers wrote. “Given the increase in levonorgestrel-releasing intrauterine system use among females at an age with some risk for breast cancer, and its likely long-term use, information about breast cancer risk should accompany discussions about benefits and risks.”
Perspective
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It is important to be intentional and accurate when we talk about data. When looking at the data in this study, you do see an association between levonorgestrel-releasing IUDs and a potential increased risk for breast cancer. It is a very small association — out of 10,000 women, there were 14 additional cases of breast cancer among those using the IUD for multiple years. This was a study done using a Danish registry database. Through this national database, the researchers compared hormonal IUD users and nonusers and did attempt to adjust for some potential confounding factors, though part of the issue here is there are many things that could be going on that cannot be accounted for in a study like this. It is fair to say the data suggest a potential, very small increased risk, as we see in studies of oral contraceptive pills. However, that association may be due to other differences between users and nonusers of IUDs and contraceptive pills in the databases that weren’t or can’t be accounted for using studies like this.
When I am caring for patients, they sometimes ask questions about contraception, and we do want to employ shared decision-making. It is reasonable to have a conversation and say, “You may have seen this recent study that was published that shows a potential very small increase in risk for breast cancer” and put that risk in context. With hormonal IUDs, there are also protective effects against other types of cancer. I would have that full conversation.
There is so much misinformation about birth control out there. We want to have conversations with patients that are centered on their needs and bring up the data, making sure we are presenting the data accurately and putting potential risks in context.
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