Tamoxifen prevention of meningioma and its proposal for the treatment of meningioma. Revisiting old data in the light of recent epidemiological observations.

Epidemiological studies reported in 2016 and 2019 demonstrated that breast cancer patients under tamoxifen treatment had significantly reduced risks of meningioma development. Tamoxifen treatment duration longer than 1500 days or with cumulative dosage higher than 26 320 mg have especially lowered risk of meningioma. Clinical long-term anticancer efficacy of tamoxifen shall associate with simultaneous suppression of estrogen receptor and downregulation of certain growth factor pathways, which may associate with - but not limited to - protein kinase-C (PKC) signaling. In this study, we will put the evidence together and indicate that tamoxifen may be effective in meningioma treatment in some patients who do not express estrogen receptor but expresses PKC, yet much higher doses of tamoxifen will be needed to treat meningiomas than those applied to treat breast cancer. We underline the fact that immunohistochemical analysis of both estrogen receptor and PKC (especially α, δ, λ and ι isoenzymes) may guide in patient stratification for selective benefitting from tamoxifen in management of meningiomas. Lastly, it would also be logical to test individual responses of meningiomas to tamoxifen in primary monolayer and spheroid cultures before starting treatment in each patient as the differential distribution of PCK isoenzymes may cause also untoward effects.