title: Risk of cancer among women with polycystic ovary syndrome: a Danish cohort study.
abstract: OBJECTIVE
  To assess the association between polycystic ovary syndrome (PCOS) and cancer, especially of the endometrium, breast and ovary.
  
  
  METHODS
  The Danish National Patient Register was used to identify 12,070 in- and outpatients in whom PCOS was diagnosed when they were aged 9-49 years during 1977-2012. Using the Danish Cancer Registry, we followed the cohort through 2012 and compared the women's cancer incidence with that of the general Danish female population by means of standardized incidence ratios (SIRs).
  
  
  RESULTS
  Cancer was diagnosed in 279 women with PCOS (SIR = 1.19; 95% CI = 1.06-1.34). We found an almost fourfold increased risk for endometrial cancer (numbers observed (N) = 16, SIR = 3.9; 95% CI = 2.2-6.3), the large majority of cases being type 1 (N = 14, SIR = 4.7; 95% CI = 2.6-7.9). We found no association between PCOS and breast (N = 59, SIR = 1.1; 95% CI = 0.8-1.4) or ovarian cancer (N = 10, SIR = 1.8; 95% CI = 0.8-3.2); however, significantly increased risks were found for kidney, colon and brain cancers.
  
  
  CONCLUSIONS
  The results of this large cohort study support those of case-control studies showing that women with PCOS are at increased risk for endometrial cancer, whereas their risks for breast and ovarian cancer are similar to those of women in the general population. Our finding that women with PCOS also are at increased risk for cancers of the kidney, colon and brain requires further study.
authors.affiliation: Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Gottschau
authors.affiliation: Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen, Denmark; Department of Gynecology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen DK-2100, Denmark.
authors.forename: Susanne Krüger
authors.initials: SK
authors.lastname: Kjaer
authors.affiliation: Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
authors.forename: Allan
authors.initials: A
authors.lastname: Jensen
authors.affiliation: Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Munk
authors.affiliation: Virus, Lifestyle and Genes, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen, Denmark. Electronic address: lene@cancer.dk.
authors.forename: Lene
authors.initials: L
authors.lastname: Mellemkjaer
mesh_terms: D000293:Adolescent; D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology*; D002648:Child; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D016889:Endometrial Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology*; D011085:Polycystic Ovary Syndrome / Q000453:epidemiology*; D012042:Registries; D055815:Young Adult
keywords: All cancer sites; Breast cancer; Cohort study; Endometrial cancer; Ovarian cancer; Polycystic ovary syndrome