Gamma knife radiosurgery for residual or recurrent intracranial hemangiopericytomas.

Residual or recurrent hemangiopericytoma (HPC) has been treated with radiosurgery; however, its long-term outcome is not well known. This study is to investigate the long-term outcome of gamma knife radiosurgery (GKS) for residual or recurrent HPCs. We conducted a retrospective analysis of 18 patients who underwent gamma knife radiosurgery for residual or recurrent HPCs. Of the 18 patients, 10 patients had high-grade HPCs (27 tumors) and 8 had low-grade HPCs (13 tumors). Median overall survival (OS) after the first GKS was 134.7months and actuarial survival rate at 1, 5, and 10years was 85.6%, 85.6%, and 37.4%, respectively. At the last follow-up, local tumor control was achieved in 32 (80.0%) of the 40 GKS-treated tumors. New lesions developed out of initial GKS target in 8 patients (44.4%). They were also treated with additional GKS. The actuarial local control rate of 40 tumors at 1-, 3-, and 5-years was 89.3%, 60.9%, and 37.5%, respectively. The median local recurrence-free interval of 40 tumors after initial GKS for each lesion was 86.1months for low-grade and 40.5months for high-grade tumors (p=0.010). Extracranial metastases developed in 7 (38.9%) patients with high-grade pathology and became a cause of death in 3 patients. Intracranial tumor control can be achieved over the long term, though additional GKS is frequently necessary. Extracranial metastasis is common in HPC of high-grade pathology. Close surveillance and aggressive treatment is recommended not only for intracranial tumor but also for possible extracranial metastases.