- High cumulative exposure to dibutyl phthalate (DBP) is associated with increased breast cancer risk, according to a Danish nationwide population-based study.
Why this matters
- Women exposed to DBP should be considered for more frequent mammography.
- Mesalazine, budesonide, lithium, and bisacodyl exceed the DBP exposure limit of 0.01 mg/kg/day.
- Population-based cohort of 1.12 million breast-cancer-free women on January 1, 2005, using a Danish Medicines Agency ingredient database, the National Prescription Registry, and the Danish Cancer Registry.
- Phthalate exposure based on prescription claims.
- Funding: Susan G. Komen for the Cure; NIH.
- More than 9.99 million women-years of follow-up (median, 10 years); 27,111 cases of invasive breast cancer occurred (estrogen receptor [ER] positive, 84%).
- Approximately 14% of the cohort (n=161,737) used phthalate-containing medications.
- Near-null associations were found for invasive breast cancer and diethyl phthalate, cellulose acetate phthalate, hypromellose phthalate, and polyvinyl acetate phthalate.
- Associations remained near-null in ER-specific models.
- The highest level of cumulative DBP exposure (≥10,000 cumulative mg) was associated with nearly doubled risk for incident breast cancer (aHR, 2.0; 95% CI, 1.1-3.6), driven entirely by an association with ER+ breast cancer (aHR, 1.9; 95% CI, 1.1-3.5).
- ER− breast cancer: aHR, 0.99; 95% CI, 0.14-7.0.
- Study could not adjust for adiposity.
- Observational design.