Epidemiology of gliomas in women diagnosed with breast cancer supports the protective role of estrogenic exposure.

Gliomas represent the most common type of brain cancers, but their etiology is still poorly understood and understanding of their risk factors is limited. The role of sex hormones in the development of brain cancers has been suggested by epidemiological and experimental studies and clinical observations, which highlighted the need for more evidence before hormone-modulating interventions are developed for prevention or treatment of gliomas. The results of this retrospective cohort study using data from SEER 9 cancer registries demonstrate a decreased risk of brain cancers in women diagnosed with breast cancers at 40+ years, which is consistent with hypothesis that estrogenic exposure reduces the risk of development of gliomas. In contrast, women diagnosed with breast cancer at < 40 years display an increased risk of subsequent brain cancers than women in general population, which likely reflects the role of shared genetic risk factors. These findings support the protective role of estrogens against development of gliomas and suggest the importance of early diagnosis and development of preventive approaches for women diagnosed at younger age (Tab. 2, Fig. 1, Ref. 37).