Hemangiopericytomas are very rare malignant vascular tumors that represent 2 to 4% of meningeal tumors. These highly vascularized tumors exhibit a high incidence of local recurrence and distant metastasis.

     Radiosurgical treatment of hemangiopericytomas has been reported in only few studies, and evolution of the tumor volume after Gamma Knife radiosurgery (GKR) has not been specifically studied.

     We report data from a patient harbouring multifocal hemangiopericytomas after several surgical removals, whole brain radiotherapy and chemotherapy.

     Gamma Knife treatment was performed to control the different tumor locations and was repeated when new lesions appeared in non-irradiated areas. Evolution of tumors volume after irradiation were measured and analyzed in serial MRI co-registered with the initial MRI on GammaPlan®.

     A total of 10 lesions were treated in 3 different Gamma Knife sessions. The mean tumor volume was 2.75cc (range 0.73-10.5cc). The median follow-up period was 24 months. The mean margin dose was 16.9 Gy (range 15-18 Gy); the mean maximum dose was 33.7 Gy (range 30-36 Gy). Of the 10 lesions irradiated, 6 have completely disappeared on the last follow-up MRI and 4 lesions showed a >90% reduction of their size.

     This is a retrospective study.

     GKR can be an effective treatment of multifocal hemangiopericytomas.

     A very important reduction of the size of these tumors can occur, even for large lesions, when a high radiation dose is used (margin dose >15 Gy).