Previous studies suggest that
hormone therapy may play an important role in the development of
meningioma. However, it is unclear whether medication with
tamoxifen can prevent
meningioma. Our study cohort included all women who were diagnosed with
breast cancer between 1961 and 2010, and a total of 227 535 women were identified with
breast cancer with a median age at diagnosis of 63 years. Women diagnosed with
breast cancer after 1987 were defined as
tamoxifen exposed; those diagnosed with
breast cancer before or during 1987 were defined as not exposed to
tamoxifen. Standardized incidence ratios (SIRs) were used to calculate the risk of subsequent
meningioma. Of these women, 223 developed
meningioma. For women without
tamoxifen exposure, the risk of
meningioma was significantly increased, with an SIR of 1.54 (95% confidence interval 1.30-1.81); the risk was not increased in those with
tamoxifen exposure (SIR=1.06, 95% confidence interval 0.84-1.32). The increased risk of
meningioma in women without
tamoxifen exposure persisted during 10 years of follow-up. In this historical cohort study, we found that women diagnosed with
breast cancer but not treated with
tamoxifen had an increased incidence of
meningioma, whereas the incidence was close to that of the general population in patients treated with
tamoxifen. This suggests that
tamoxifen may prevent the development of
meningioma.