Dramatic Shrinkage with Reduced Vascularization of Large Meningiomas After Cessation of Progestin Treatment

Background The relationship between long-term intake of progestin and meningioma growth is now well-known and has become a model of hormone-driven meningioma growth. Conversely, it has been demonstrated that cessation of treatment often leads to tumor regression. Consequently, watchful observation has become the strategy of choice in the case of multiple meningiomas in asymptomatic patients undergoing progestin treatment. Case Description In 2 patients with large tumors (>60 cm 3 ) scheduled for surgery, conservative management with cessation of progestin treatment produced a dramatic reduction of meningioma size from 64 to 11 cm 3 (−83%) and 68 to 13 cm 3 (−81%), respectively, during a 1-year period. This shrinkage was associated with spontaneous devascularization of the meningiomas as observed on T2-weighted images. Conclusions This observation adds new insights into the role of progesterone in meningioma tumorigenesis and could lead to future discoveries on the molecular relationships between meningioma tumorigenesis, progesterone dependence, and tumor vascularization.