Is Intrauterine Hormonal Contraception Associated With Increased Breast Cancer Risk?

By: Chris Schimpf, MSW
Posted: Tuesday, November 26, 2024

Use of contraceptive levonorgestrel-releasing intrauterine systems may be associated with an increased risk of breast cancer, according to the findings of a Danish study published as a research letter in JAMA. Charlotte Wessel Skovlund, MSc, PhD, of The Danish Cancer Institute, Copenhagen, and colleagues found in their nationwide study of women between the ages of 15 and 49 that breast cancer risk increased by 14 per 10,000 women when using the popular hormonal contraception. No increase in risk was observed with the duration of use.

“Given the increase in [use of this method of contraception] 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,” the researchers stated.

A total of 78,595 new users of levonorgestrel-releasing intrauterine systems and 78,595 nonusers of hormonal contraceptives were included in the study, drawn from nationwide Danish registers. All users of the intrauterine systems began using them between 2000 and 2019 and were matched 1:1 with nonusers by birth year. The mean age of participants was 38 (standard deviation = 7.7 years).

The investigators reported that the hazard ratio for breast cancer was found to be 1.4 with use of the intrauterine systems compared with nonuse of hormonal contraceptives entirely (95% confidence interval [CI] = 1.2–1.5). Regarding the duration of use, the hazard ratios were 1.3 for 0 to 5 years (95% CI = 1.1–1.5), 1.4 for more than 5 to 10 years (95% CI = 1.1–1.7), and 1.8 for more than 10 to 15 years (95% CI = 1.2–2.6) compared with corresponding durations of nonuse. This resulted in an excess of 14 (95% CI = 6–23), 29 (95% CI = 9–50), and 71 (95% CI = 15–127) breast cancer diagnoses per 10,000 users, respectively.

Disclosure: The study authors reported no conflicts of interest.

JAMA