Long-acting intrauterine contraceptive device may raise breast cancer risk

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.”