title: Cancer risk in women using the levonorgestrel-releasing intrauterine system in Finland.
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).
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  II.
authors.affiliation: Department of Obstetrics and Gynecology, Hyvinkää Hospital, Hyvinkää, the Department of Obstetrics and Gynecology, Turku University Hospital, and the University of Turku, Turku, the Schools of Medicine and Health Sciences, University of Tampere, and the Department of Obstetrics and Gynecology, Tampere University Hospital, Tampere, and the Department of Obstetrics and Gynecology, Helsinki University Hospital, the University of Helsinki, and the Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland.
authors.forename: Tuuli
authors.initials: T
authors.lastname: Soini
authors.forename: Ritva
authors.initials: R
authors.lastname: Hurskainen
authors.forename: Seija
authors.initials: S
authors.lastname: Grénman
authors.forename: Johanna
authors.initials: J
authors.lastname: Mäenpää
authors.forename: Jorma
authors.initials: J
authors.lastname: Paavonen
authors.forename: Eero
authors.initials: E
authors.lastname: Pukkala
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology; D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology; D003271:Contraceptive Agents, Female / Q000008:administration & dosage*; D016889:Endometrial Neoplasms / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007436:Intrauterine Devices, Medicated; D016912:Levonorgestrel / Q000008:administration & dosage*; D008175:Lung Neoplasms / Q000453:epidemiology; D008595:Menorrhagia / Q000628:therapy; D008875:Middle Aged; D009369:Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D010051:Ovarian Neoplasms / Q000453:epidemiology; D010190:Pancreatic Neoplasms / Q000453:epidemiology; D012042:Registries
chemical_list: D003271:Contraceptive Agents, Female; D016912:Levonorgestrel