Heavy-charged-particle radiosurgery for intracranial arteriovenous malformations.

We have treated over 400 patients with symptomatic inoperable intracranial arteriovenous malformations (AVMs) with stereotactic heavy-charged-particle Bragg peak radiosurgery at the University of California at Berkeley in a collaborative program with Stanford University Medical Center and the University of California Medical Center, San Francisco. A long-term dose-searching clinical trial protocol has been developed and we have followed more than 250 patients for more than 2 years. Initially, radiation doses ranged from 45 to 35 GyE, and now doses of 25, 20, 15 and, under special circumstances, 10 GyE, depending on a number of factors, are being evaluated. The characteristics of charged-particle beams provide a relatively homogeneous dose distribution with the 90% isodose contour to the periphery of the lesion. When the entire arterial phase of the AVM core is included in the treatment field, the rates for complete obliteration 3 years after treatment are: 90-95% for volumes less than or equal to 4 cm3; 90-95% for volumes greater than 4 and less than or equal to 14 cm3; and 60-70% for volumes greater than 14 cm3. The total obliteration rate for all volumes up to 70 cm3 is approximately 80-85%. For complete radiation-induced obliteration there is a relationship of dose and volume primarily, and location secondarily. Results on relationships between dose, AVM obliteration, and complications and sequelae of the radiosurgical procedure are presented and discussed.