Progesterone-releasing IUD associated with a Higher than expected Incidence of Breast Cancer

Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland

Finnish researchers found that certain forms of IUD may actually put women at higher risk for breast cancer. The Hyvinkää Hospital study looked at the levonorgestrel-releasing intrauterine system (LNG-IUS) – or progesterone-releasing IUD – used as a contraceptive and also to treat women who suffer from heavy periods, endometriosis, and chronic pelvic pain.

Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland

Abstract

Obstetrics & Gynecology logo
Levonorgestrel-releasing intrauterine system use was associated with a higher than expected incidence of breast cancer.

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.

Sources:
  • Cancer Risk in Women Using the Levonorgestrel-Releasing Intrauterine System in Finland,
    NCBI, PMID: 25004338, Obstet Gynecol. 2014 Jul 7
  • IUD may carry higher risk for breast cancer in certain women,
    CNN, July 9, 2014
  • Breast Cancer Risk for Women Increases With IUD Study Suggests,
    GuardianLV, July 10, 2014

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