Finasteride treatment and male breast cancer

a register-based cohort study in four Nordic countries

Mathias Meijer, Lau Caspar Thygesen, Anders Green, Martha Emneus, Klaus Brasso, Peter Iversen, Eero Pukkala, Kristian Bolin, Knut Stavem, Annette K Ersbøll

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Abstract

A potential link has been suggested between dispensed finasteride and increased risk of male breast cancer (MBC). Due to the rare occurrence of MBC, it remains to be established if such a relationship exists. The purpose of this study was to combine nationwide registers in four countries to assess the potential association between dispensed finasteride and MBC. A cohort of all males with dispensed finasteride in Denmark, Finland, Norway, and Sweden (1,365,088 person years) was followed up for up to 15 years for breast cancer, and compared to a cohort of males unexposed to finasteride. Individual-level register data included country, dates of dispensed finasteride, MBC diagnosis, and death. Incidence rate ratios (IRRs) were estimated using a generalized linear model with a Poisson distribution. An increased risk of MBC was found among finasteride users (IRR = 1.44, 95% confidence interval [95% CI] = 1.11-1.88) compared to nonusers. The IRR increased to 1.60 (95% CI = 1.20-2.13) when users in Norway and Sweden with short follow-up time were excluded. The highest IRR was seen among men with medium duration of dispensed finasteride, medium accumulated consumption of finasteride, and among men with first dispensed finasteride prescription 1-3 years prior to diagnosis. The analyses suggested possible ascertainment bias and did not support a clear relationship between dispensed finasteride and MBC. In conclusion, a significant association between dispensed finasteride and MBC was identified. However, due to limited data for adjustment of potential confounding and surveillance bias in the present study, further research is needed to confirm these results.

Original languageEnglish
JournalCancer Medicine
Volume7
Issue number1
Pages (from-to)254–260
ISSN2045-7634
DOIs
Publication statusPublished - Jan 2018

Fingerprint

Male Breast Neoplasms
Finasteride
Scandinavian and Nordic Countries
Cohort Studies
Incidence
Norway
Confidence Intervals
Poisson Distribution
Denmark
Finland
Prescriptions
Linear Models
Research Design

Keywords

  • Breast neoplasms male
  • Nordic countries
  • finasteride
  • pharmacoepidemiology
  • prostatic neoplasms
  • registers

Cite this

Meijer, Mathias ; Thygesen, Lau Caspar ; Green, Anders ; Emneus, Martha ; Brasso, Klaus ; Iversen, Peter ; Pukkala, Eero ; Bolin, Kristian ; Stavem, Knut ; Ersbøll, Annette K. / Finasteride treatment and male breast cancer : a register-based cohort study in four Nordic countries. In: Cancer Medicine. 2018 ; Vol. 7, No. 1. pp. 254–260.
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title = "Finasteride treatment and male breast cancer: a register-based cohort study in four Nordic countries",
abstract = "A potential link has been suggested between dispensed finasteride and increased risk of male breast cancer (MBC). Due to the rare occurrence of MBC, it remains to be established if such a relationship exists. The purpose of this study was to combine nationwide registers in four countries to assess the potential association between dispensed finasteride and MBC. A cohort of all males with dispensed finasteride in Denmark, Finland, Norway, and Sweden (1,365,088 person years) was followed up for up to 15 years for breast cancer, and compared to a cohort of males unexposed to finasteride. Individual-level register data included country, dates of dispensed finasteride, MBC diagnosis, and death. Incidence rate ratios (IRRs) were estimated using a generalized linear model with a Poisson distribution. An increased risk of MBC was found among finasteride users (IRR = 1.44, 95{\%} confidence interval [95{\%} CI] = 1.11-1.88) compared to nonusers. The IRR increased to 1.60 (95{\%} CI = 1.20-2.13) when users in Norway and Sweden with short follow-up time were excluded. The highest IRR was seen among men with medium duration of dispensed finasteride, medium accumulated consumption of finasteride, and among men with first dispensed finasteride prescription 1-3 years prior to diagnosis. The analyses suggested possible ascertainment bias and did not support a clear relationship between dispensed finasteride and MBC. In conclusion, a significant association between dispensed finasteride and MBC was identified. However, due to limited data for adjustment of potential confounding and surveillance bias in the present study, further research is needed to confirm these results.",
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Finasteride treatment and male breast cancer : a register-based cohort study in four Nordic countries. / Meijer, Mathias; Thygesen, Lau Caspar; Green, Anders; Emneus, Martha; Brasso, Klaus; Iversen, Peter; Pukkala, Eero; Bolin, Kristian; Stavem, Knut; Ersbøll, Annette K.

In: Cancer Medicine, Vol. 7, No. 1, 01.2018, p. 254–260.

Research output: Contribution to journalJournal articleResearchpeer-review

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T1 - Finasteride treatment and male breast cancer

T2 - a register-based cohort study in four Nordic countries

AU - Meijer, Mathias

AU - Thygesen, Lau Caspar

AU - Green, Anders

AU - Emneus, Martha

AU - Brasso, Klaus

AU - Iversen, Peter

AU - Pukkala, Eero

AU - Bolin, Kristian

AU - Stavem, Knut

AU - Ersbøll, Annette K

N1 - © 2017 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

PY - 2018/1

Y1 - 2018/1

N2 - A potential link has been suggested between dispensed finasteride and increased risk of male breast cancer (MBC). Due to the rare occurrence of MBC, it remains to be established if such a relationship exists. The purpose of this study was to combine nationwide registers in four countries to assess the potential association between dispensed finasteride and MBC. A cohort of all males with dispensed finasteride in Denmark, Finland, Norway, and Sweden (1,365,088 person years) was followed up for up to 15 years for breast cancer, and compared to a cohort of males unexposed to finasteride. Individual-level register data included country, dates of dispensed finasteride, MBC diagnosis, and death. Incidence rate ratios (IRRs) were estimated using a generalized linear model with a Poisson distribution. An increased risk of MBC was found among finasteride users (IRR = 1.44, 95% confidence interval [95% CI] = 1.11-1.88) compared to nonusers. The IRR increased to 1.60 (95% CI = 1.20-2.13) when users in Norway and Sweden with short follow-up time were excluded. The highest IRR was seen among men with medium duration of dispensed finasteride, medium accumulated consumption of finasteride, and among men with first dispensed finasteride prescription 1-3 years prior to diagnosis. The analyses suggested possible ascertainment bias and did not support a clear relationship between dispensed finasteride and MBC. In conclusion, a significant association between dispensed finasteride and MBC was identified. However, due to limited data for adjustment of potential confounding and surveillance bias in the present study, further research is needed to confirm these results.

AB - A potential link has been suggested between dispensed finasteride and increased risk of male breast cancer (MBC). Due to the rare occurrence of MBC, it remains to be established if such a relationship exists. The purpose of this study was to combine nationwide registers in four countries to assess the potential association between dispensed finasteride and MBC. A cohort of all males with dispensed finasteride in Denmark, Finland, Norway, and Sweden (1,365,088 person years) was followed up for up to 15 years for breast cancer, and compared to a cohort of males unexposed to finasteride. Individual-level register data included country, dates of dispensed finasteride, MBC diagnosis, and death. Incidence rate ratios (IRRs) were estimated using a generalized linear model with a Poisson distribution. An increased risk of MBC was found among finasteride users (IRR = 1.44, 95% confidence interval [95% CI] = 1.11-1.88) compared to nonusers. The IRR increased to 1.60 (95% CI = 1.20-2.13) when users in Norway and Sweden with short follow-up time were excluded. The highest IRR was seen among men with medium duration of dispensed finasteride, medium accumulated consumption of finasteride, and among men with first dispensed finasteride prescription 1-3 years prior to diagnosis. The analyses suggested possible ascertainment bias and did not support a clear relationship between dispensed finasteride and MBC. In conclusion, a significant association between dispensed finasteride and MBC was identified. However, due to limited data for adjustment of potential confounding and surveillance bias in the present study, further research is needed to confirm these results.

KW - Breast neoplasms male

KW - Nordic countries

KW - finasteride

KW - pharmacoepidemiology

KW - prostatic neoplasms

KW - registers

U2 - 10.1002/cam4.1273

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VL - 7

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EP - 260

JO - Cancer Medicine

JF - Cancer Medicine

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