title: Male breast cancer and 5α-reductase inhibitors finasteride and dutasteride.
abstract: OBJECTIVE
  We examined the association between 5α-reductase inhibitors and male breast cancer.
  
  
  METHODS
  Study participants were men 40 to 85 years old, with prescription and medical coverage, enrolled in the United States IMS LifeLink™ Health Plan claims database between 2001 and 2009. Cases required a primary breast cancer diagnosis (ICD-9-CM 175.x) on 2 different dates and a procedural code for mastectomy or lumpectomy/partial mastectomy with evidence of continuous care (radiation/chemotherapy or diagnoses in 2 or more months). Eligible controls were within 5 years in age and had duration of prior health care enrollment within 6 weeks. Risk set sampling selected 20 controls per case. We assessed the rate ratio for male breast cancer with 5α-reductase inhibitor exposure using conditional logistic regression. Analyses were stratified by duration of health care enrollment before diagnosis (1 year or more, 2 years or more and 3 years or more), each incremental 180 and 365 days of cumulative 5α-reductase inhibitor exposure, and period specific time frames before diagnosis (years 1, 2 and 3).
  
  
  RESULTS
  We identified 339 breast cancer cases matched to 6,780 controls. No statistically significant associations were observed between 5α-reductase inhibitors and breast cancer regardless of exposure assessment before the index date (1 year or more-RR 0.70, 95% CI 0.34-1.45; 2 years or more-RR 0.59, 95% CI 0.24-1.48; or 3 years or more-RR 0.75, 95% CI 0.27-2.10). Each subsequent 180 days (RR 1.02, 95% CI 0.67-1.53) and 365 days (RR 1.03, 95% CI 0.45-2.37) of cumulative 5α-reductase inhibitor therapy and period specific rate ratios also showed null associations.
  
  
  CONCLUSIONS
  The lack of an association in our study suggests that the development of breast cancer should not influence the prescribing of 5α-reductase inhibitor therapy.
authors.affiliation: U.S. Department of Health and Human Services/U.S. Food and Drug Administration/Center for Drug Evaluation and Research/Office of Pharmacovigilance and Epidemiology, Office of Surveillance and Epidemiology/Department of Epidemiology, Silver Spring, Maryland; Department of Pharmaceutical Outcomes & Policy, College of Pharmacy, University of Florida, Gainesville, Florida.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Bird
authors.forename: James M
authors.initials: JM
authors.lastname: Brophy
authors.forename: Abraham G
authors.initials: AG
authors.lastname: Hartzema
authors.forename: Joseph A C
authors.initials: JA
authors.lastname: Delaney
authors.forename: Mahyar
authors.initials: M
authors.lastname: Etminan
mesh_terms: D058891:5-alpha Reductase Inhibitors / Q000009:adverse effects*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001378:Azasteroids / Q000009:adverse effects*; D018567:Breast Neoplasms, Male / Q000139:chemically induced* / Q000453:epidemiology*; D000068538:Dutasteride; D018120:Finasteride / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D058891:5-alpha Reductase Inhibitors; D001378:Azasteroids; D018120:Finasteride; D000068538:Dutasteride
keywords: 5-alpha reductase inhibitors; 5ARI; 5α-reductase inhibitor; FDA; Food and Drug Administration; PPV; breast neoplasms; male; positive predictive value