307P - Exposure to Di-2-ethylhexyl phthalate and breast cancer incidence: A cohort study

Background

Phthalates are ubiquitous environmental endocrine disruptors. As the predominant phthalate, di-2-ethylhexyl phthalate (DEHP) has been considered possibly carcinogenic to humans but large-scale longitudinal evidence is needed to further clarify its carcinogenicity. To examine the association between DEHP exposure and incidence of breast cancer, specifically focusing on hormone receptor-positive breast cancer.

Methods

A total of 273,295 women from UK Biobank cohort were followed up for a median of 13.5 years. Disease information was collected from National Health Service Cancer Registry and National Death Index. Baseline and yearly-average level of DEHP exposure were estimated for each individual by linking chemical monitoring record of European Environment Agency with home address of the participants by Kriging interpolation model. Cox proportional hazard model was employed to estimate the association between DEHP exposure and breast cancer.

Results

The median (IQR) of baseline and yearly-average DEHP concentration were 8,000.25 (interquartile range: 6,657.85-11,948.83) and 8,000.25 (interquartile range: 1,819.93-11,359.55) μg/L. No association between baseline DEHP exposure and breast cancer incidence was found. As for yearly-average exposure, each quartile of DEHP was positively associated with higher risk of breast cancer (HR,1.05; 95%CI, 1.03,1.07, p<0.001). The third quartile of yearly-average DEHP was associated with 3.94 fold risk of hormone receptor-positive breast cancer (95%CI, 3.212, 4.81, p<0.001). Stratification analyses showed that the risk of hormone receptor-positive breast cancer is higher than that of hormone receptor-negative breast cancer (p = 0.039). Furthermore, no significant modification effect on the DEHP-neoplasm relationship by menopausal status or ethnicity but a suggestive higher risk in younger women and those who underwent oral contraceptive pill therapy. In sensitivity analysis, the associations remained when excluding the cases diagnosed within 2 years post baseline.

Conclusions

Real-world level of DEHP exposure was associated with higher risk of breast cancer. Because of the health risks associated with DEHP, its release to the environment should be managed.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.