Objectives:

Hemangiopericytomas are relatively uncommon and arise from the Zimmermann pericytes that line the walls of small blood vessels. The conventional treatment approach involves gross total resection (GTR), followed by adjuvant radiotherapy. However, due to their tendency to invade the dural sinuses, high vascularity, and their anatomical inaccessibility, radical resection may be unsafe with substantial risk of recurrence. To address this challenge, stereotactic radiosurgery (SRS) has been proposed as a postoperative adjuvant therapy. The current study aims to evaluate the role of CyberKnife SRS in the treatment of residual, recurrent, and metastatic hemangiopericytomas based on a retrospective analysis of patient data at Stanford University Medical Center.

Methods:

Over the course of 24 years from 1998 to 2023, 27 patients with 101 tumors underwent CyberKnife SRS, with a median patient age of 51 years at the time of treatment. The median follow-up period from SRS was 103 months. All patients underwent upfront surgical resection.

Results:

The median tumor volume was 1.5 cc. The median marginal and maximum radiosurgical doses to the tumors were 20 Gy and 26.9 Gy, delivered in 1 to 5 fractions. The results showed that 24 of the 101 (23.8%) treated tumors progressed, with a median time to recurrence of 30 months. At 10 years, the rates of local tumor control (LTC), overall survival (OS), and progression-free survival (PFS) were 74.3%, 80.8%, and 67%, respectively. In patients with residual lesions, the LTC rates were significantly greater when compared to those with residual and metastatic tumors. Regarding the OS and PFS, there was no significant difference between patients with residual, recurrent, and metastatic hemangiopericytomas. No cases of radiation necrosis were detected.

Conclusion(s):

This is the largest single-institutional retrospective series with the longest follow-up of hemangiopericytomas treated with SRS, up to date. SRS leads to excellent LTC, PFS and OS at 10 years, with negligible risk for radiation necrosis. Thus, SRS is an effective and safe management option for residual, recurrent, and metastatic hemangiopericytomas.