title: Long-term use of 5α-reductase inhibitors and the risk of male breast cancer.
abstract: BACKGROUND
  The 5α-reductase inhibitors (5-ARI) finasteride and dutasteride are indicated for the treatment of lower urinary tract symptoms caused by benign prostatic hyperplasia. Case reports have suggested that 5-ARIs increase the risk for male breast cancer, with no conclusive evidence. The objective of this study was to quantify the association between use of 5-ARIs and the risk for male breast cancer.
  
  
  METHODS
  A case-control study was conducted with data from the United Kingdom Clinical Practice Research Datalink database among all men aged 45 years and older in the period 1 January 1992 to 31 December 2011. Cases of men diagnosed with breast cancer were matched to up 10 controls on age and general practice. Crude and adjusted odds ratios were estimated for the risk of breast cancer associated with the use of 5-ARIs.
  
  
  RESULTS
  Three hundred and ninety-eight cases were identified and matched to 3,930 controls. Ever use of 5-ARIs was associated with an adjusted odds ratio for breast cancer of 1.08 (95 % CI 0.62-1.87) compared to non-users. Increasing cumulative duration of treatment showed no increasing risks: adjusted odds ratios for use for less than 280, for 280 to 1,036 and for more than 1,036 days were 1.21 (95 % CI 0.47-3.10), 0.94 (95 % CI 0.36-2.41) and 1.29 (95 % CI 0.54-3.08), respectively.
  
  
  CONCLUSIONS
  In this study, there was no evidence of an association between short- or long-term treatment with 5-ARIs and the risk for breast cancer in older men.
authors.affiliation: Division of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands, R.G.Duijnhoven@uu.nl.
authors.forename: Ruben G
authors.initials: RG
authors.lastname: Duijnhoven
authors.forename: Sabine M J M
authors.initials: SM
authors.lastname: Straus
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Souverein
authors.forename: Anthonius
authors.initials: A
authors.lastname: de Boer
authors.forename: J L H Ruud
authors.initials: JL
authors.lastname: Bosch
authors.forename: Arno W
authors.initials: AW
authors.lastname: Hoes
authors.forename: Marie L
authors.initials: ML
authors.lastname: De Bruin
mesh_terms: D058891:5-alpha Reductase Inhibitors / Q000008:administration & dosage / Q000009:adverse effects*; D000368:Aged; D000369:Aged, 80 and over; D018567:Breast Neoplasms, Male / Q000453:epidemiology* / Q000209:etiology; D016022:Case-Control Studies; D000068538:Dutasteride / Q000008:administration & dosage / Q000009:adverse effects; D018120:Finasteride / Q000008:administration & dosage / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D011470:Prostatic Hyperplasia / Q000188:drug therapy; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D058891:5-alpha Reductase Inhibitors; D018120:Finasteride; D000068538:Dutasteride