Stereotactic radiosurgery of cerebral arteriovenous malformations with a multileaf collimator and a single isocenter

To prospectively demonstrate the safety and efficacy of stereotactic radiosurgery for arteriovenous malformations (AVMs) of the brain with a linear accelerator fitted with a multileaf collimator.

A novel radiosurgery system was developed at the University of Michigan Medical Center with a standard multileaf collimator and a computer-controlled radiotherapy system. Data were accumulated prospectively on all patients undergoing treatment with this system since treatment began in 1995.

Thirty-six patients with 37 AVMs have undergone treatment to date. At more than 3 years since treatment, 15 of 16 AVMs with a volume of less than 10 cc were proven to be obliterated by angiography or magnetic resonance imaging, and one was considered a treatment failure. At more than 24 months since therapy, all four AVMs with a volume of 10 to 25 cc were obliterated. Four patients with AVMs with a volume of more than 25 cc have undergone staged therapy, treating the entire volume to 10 Gy twice, but none has been followed long enough to demonstrate a final outcome. There were four transient and no permanent complications.

Our early data indicate that stereotactic radiosurgery of cerebral AVMs with a linear accelerator and a multileaf collimator is safe and effective. Large AVMs may be especially suitable for this mode of therapy. Staged treatment of very large AVMs seems to be a promising addition to standard treatment, but longer follow-up is necessary to confirm that complete obliteration can be achieved.