A Report of Tamoxifen and Parkinson's Disease in a US Population and a Review of the Literature

Background: Tamoxifen, a selective estrogen receptor modulator, has been shown to variably affect Parkinson's disease (PD) risk. Objective: The aim of this study was to review epidemiological literature and evaluate the rate of PD in women with breast cancer with tamoxifen exposure in a US population. Methods: A literature search was conducted to identify relevant studies. We performed a retrospective cohort analysis using the Nurses' Health Study Version One to report descriptive statistics. Results: Most studies suggest there may be a time-dependent effect of tamoxifen on PD risk, with the risk increasing with time from exposure. However, rates of PD in persons exposed to tamoxifen overall appear to be low. In our cohort, PD was evident in 6.2 per 1,000 of those with tamoxifen use and 3.6 per 1,000 of those without tamoxifen use. Time from breast cancer to PD diagnosis was 9.7 years among women with tamoxifen exposure and 11.7 among women without. Conclusions: Tamoxifen may be associated with an increased risk for PD. Further research is needed to elucidate the role of estrogen and selective estrogen antagonism in PD.