Intrauterine contraceptive (progestogen) and breast cancer risk

A Danish study (78,595 new users; 78,595 non-users) found link between levonorgestrel-releasing intrauterine systems (LNG-IUSs) and increased breast cancer risk in females aged 15-49 years, vs non-use (hazard ratio 1.4; 95% confidence interval, 1.2-1.5) (1)

• the absolute risk low but there was excess risk of 14/10 000
• the risk did not increase with duration of use

The Danish study evidence contrasts with the results from a systematic review and meta-analysis by Heting et al (2):

• results suggested that LNG-IUS was not a risk factor for breast cancer
• the study authors note though that:
  • since there were six articles that were not included in the meta-analysis and their data were not used, we should be cautious about this conclusion

Reference:

1. Mørch LS, Meaidi A, Corn G, Hargreave M, Wessel Skovlund C. Breast Cancer in Users of Levonorgestrel-Releasing Intrauterine Systems. JAMA. Published online October 16, 2024.
2. Heting M et al. Levonorgestrel intrauterine system and breast cancer risk: An updated systematic review and meta-analysis of observational studies. Heliyon. 2023 Mar 22;9(4):e14733.