Dempsey, Jacqueline M.Kidwell, Kelley M.Gersch, Christina LPesch, Andrea MDesta, ZeruesenayStorniolo, Anna MariaStearns, VeredSkaar, Todd C.Hayes, Daniel FHenry, N LynnRae, James MHertz, Daniel L2020-11-092020-11-092019-06-13Dempsey, J. M., Kidwell, K. M., Gersch, C. L., Pesch, A. M., Desta, Z., Storniolo, A. M., Stearns, V., Skaar, T. C., Hayes, D. F., Henry, N. L., Rae, J. M., & Hertz, D. L. (2019). Effects of SLCO1B1 polymorphisms on plasma estrogen concentrations in women with breast cancer receiving aromatase inhibitors exemestane and letrozole. Pharmacogenomics, 20(8), 571–580. https://doi.org/10.2217/pgs-2019-00201462-2416https://hdl.handle.net/1805/24343Aim: This study tested for associations between SLCO1B1 polymorphisms and circulating estrogen levels in women with breast cancer treated with letrozole or exemestane. Patients & methods: Postmenopausal women with hormone-receptor positive breast cancer were genotyped for SLCO1B1*5 (rs4149056) and rs10841753. Pretreatment and on-treatment plasma estrogens and aromatase inhibitor (AI) concentrations were measured. Regression analyses were performed to test for pharmacogenetic associations with estrogens and drug concentrations. Results: SLCO1B1*5 was associated with elevated pretreatment estrone sulfate and an increased risk of detectable estrone concentrations after 3 months of AI treatment. Conclusion: These findings suggest SLCO1B1 polymorphisms may have an effect on estrogenic response to AI treatment, and therefore may adversely impact the anticancer effectiveness of these agents.en-USbreast cancerexemestaneletrozolepharmacogenomicsSLCO1B1Article