- 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.
- 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.
- 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).
- Observational design.