20-year study nixes link between fertility drugs, breast cancer

  • Guleria S & al.
  • Cancer Epidemiol Biomarkers Prev
  • 18 Sep 2019

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • A nationwide Danish cohort study with 20 years of follow-up failed to find an association between fertility drugs and breast cancer.

Why this matters

  • Findings ought to be reassuring to women treated with fertility drugs.

Study design

  • Nationwide retrospective cohort, using several Danish registries, of 1,330,852 women aged 20-44 years (1995-2011).
  • Funding: Danish Cancer Society; Novo Nordisk Foundation; others.

Key results

  • 7.3% of the cohort was infertile and 1.5% of the cohort was diagnosed with breast cancer during a median follow-up of 20.9 years.
  • Infertile women treated with any fertility drugs (vs fertile women) were not at increased risk for breast cancer (HR, 1.02; 95% CI, 0.95-1.10).
  • Individual analysis by drug type found no association for:
    • Clomiphene citrate (HR, 1.02; 95% CI, 0.93-1.12).
    • Gonadotropins (HR, 1.01; 95% CI, 0.92-1.11).
    • Human chorionic gonadotropin (HR, 1.01; 95% CI, 0.92-1.10).
    • Gonadotropin-releasing hormone analogs (HR, 1.05; 95% CI, 0.94-1.16).
    • Progesterone (HR, 1.07; 95% CI, 0.96-1.19).
  • No association was found with fertility drugs by breast cancer subtype:
    • Ductal: HR, 1.01 (95% CI, 0.93-1.10).
    • Lobular: HR, 1.12 (95% CI, 0.87-1.44).
    • Mucinous: HR, 0.90 (95% CI, 0.43-1.87).

Limitations

  • Observational design.