The Relationship Of Hormone Exposure In Breast Cancer And Subsequent Risk Of High Grade Gliomas

Abstract BACKGROUND Women have a lower incidence of high grade gliomas (HGGs), which is thought to be related to sex differences and hormone exposure. The association between hormone dependent tumors in women and HGGs remains poorly investigated. METHODS The Surveillance, Epidemiology, and End Results (SEER) database of 18 Registries (2000–2017) was used to assess age-adjusted incidence rates and temporal trends of breast cancer (BC) and HGG. Female BC patients 18 years of age or older and with ductal or lobular BC were then assessed for the risk of subsequent HGG, calculated as the standardized incidence ratio (SIR). RESULTS A total of 976,134 patients diagnosed with BC between 2000–2017 were identified. The temporal trend of BC and HGG incidence rates remained comparable throughout the study, with a higher incidence of BC and lower incidence of HGGs in females. Female BC patients had a 22% lower risk of developing a HGG (SIR 0.78 [0.69–0.87], p< 0.05) compared to general population. HGG risk by age groups in BC females was significant, with a lower risk found in pre-menopausal women (Ages 18–50, SIR 0.66 [0.45–0.94] vs Ages 50+ SIR 0.79 [0.70–0.89], p< 0.05 for both). Among HGG tumors, a decreased risk of developing glioblastoma (SIR 0.83 [0.75–0.93], p< 0.05) and anaplastic astrocytoma (SIR 0.58 [0.35–90, p< 0.05), was found, but not for anaplastic oligodendrogliomas. CONCLUSIONS The findings of our study allude to the protective effect of hormone exposure in the development of HGGs, as shown by the lower risk in female patients with BC compared to the general population.