Cancer risk in women using the levonorgestrel-releasing intrauterine system in Finland

Obstet Gynecol. 2014 Aug;124(2 Pt 1):292-9. doi: 10.1097/AOG.0000000000000356.

Abstract

Objective: To examine the association between premenopausal use of the levonorgestrel-releasing intrauterine system and cancer incidence in Finland with a special focus on endometrial adenocarcinoma.

Methods: All Finnish women aged 30-49 years using a levonorgestrel-releasing intrauterine system for treatment of menorrhagia in 1994-2007 (n=93,843) were identified from the National Reimbursement Registry and linked to the Finnish Cancer Registry data. The incidence of cancers in levonorgestrel-releasing intrauterine system users was compared with that in the general population.

Results: A total of 2,781 cancer cases were detected in levonorgestrel-releasing intrauterine system users during the follow-up of 855,324 women-years. The standardized incidence ratio (observed-to-expected ratio) for endometrial adenocarcinoma was 0.50 (95% confidence interval [CI] 0.35-0.70; 34 observed compared with 68 expected cases) after the first levonorgestrel-releasing intrauterine system purchase and 0.25 (95% CI 0.05-0.73; three observed compared with 12 expected cases) after two purchases. The standardized incidence ratio for ovarian cancer was 0.60 (95% CI 0.45-0.76; 59 observed compared with 99 expected cases), for pancreatic cancer 0.50 (95% CI 0.28-0.81; 15 observed compared with 30 expected cases), and for lung cancer 0.68 (95% CI 0.49-0.91; 43 observed compared with 63 expected cases). The standardized incidence ratio for breast cancer among all levonorgestrel-releasing intrauterine system users was 1.19 (95% CI 1.13-1.25; 1,542 observed compared with 1,292 expected cases).

Conclusion: The levonorgestrel-releasing intrauterine system may have a protective effect against endometrial malignant transformation. Using the levonorgestrel-releasing intrauterine system for treatment of menorrhagia during reproductive years was associated with a lower incidence of endometrial, ovarian, pancreatic, and lung cancers than expected. Levonorgestrel-releasing intrauterine system use was associated with a higher than expected incidence of breast cancer.

Level of evidence: II.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / epidemiology
  • Adult
  • Breast Neoplasms / epidemiology
  • Contraceptive Agents, Female / administration & dosage*
  • Endometrial Neoplasms / epidemiology
  • Female
  • Finland / epidemiology
  • Follow-Up Studies
  • Humans
  • Incidence
  • Intrauterine Devices, Medicated*
  • Levonorgestrel / administration & dosage*
  • Lung Neoplasms / epidemiology
  • Menorrhagia / therapy
  • Middle Aged
  • Neoplasms / epidemiology*
  • Neoplasms / prevention & control
  • Ovarian Neoplasms / epidemiology
  • Pancreatic Neoplasms / epidemiology
  • Registries

Substances

  • Contraceptive Agents, Female
  • Levonorgestrel