The Study: Phthalates happen to be used in the manufacture of time-release medication capsules. Biologically these chemicals can mimic the behavior of hormones, which has raised pre-clinical concern of their potential influence on breast cancer. What country could give us some really good epidemiological data on this subject? Facebook! No, but close. Denmark! Correct, and it was our second choice too. Because the Danes record everyone’s medications, they have very accurate records of exactly what medications contain phthalates and can therefore estimate a person’s medication-related phthalate exposure and related risk. The cohort consisted of over 1.1 million women of whom 14% filled prescriptions for phthalate medications. And there was a pretty broad phthalate content ranging from 0.003 to 150 milligrams per capsule. There were just over 27,000 cases of breast cancer, of which 85% were estrogen receptor(+). Among women with “very high” (10K mg cumulatively) phthalate exposure, there was a 2-fold increase in the risk of estrogen receptor(+) breast cancer, while women with lower exposure had no increased risk.
Bottom Line: A high threshold of phthalate exposure from medications appears to be associated with an increased risk of developing estrogen receptor(+) breast cancer. | Ahern, J Clin Oncol 2019