Background: Heavy-charged-particle radiation has several advantages over protons and photons for the treatment of intracranial lesions; it has an improved physical distribution of the dose deep in tissue, a small angle of lateral scattering, and a sharp distal falloff of the dose.
Methods: We present detailed clinical and radiologic follow-up in 86 patients with symptomatic but surgically inaccessible cerebral arteriovenous malformations that were treated with stereotactic helium-ion Bragg-peak radiation. The doses ranged from 8.8 to 34.6 Gy delivered to volumes of tissue of 0.3 to 70 cm3.
Results: Two years after radiation treatment, the rate of complete obliteration of the lesions, as detected angiographically, was 94 percent for lesions smaller than 4 cm3, 75 percent for those of 4 to 25 cm3, and 39 percent for those larger than 25 cm3. After three years, the rates of obliteration were 100, 95, and 70 percent, respectively. Major neurologic complications occurred in 10 patients (12 percent), of whom 8 had permanent deficits. All these complications occurred in the initial stage of the protocol, before the maximal dose of radiation was reduced to 19.2 Gy. In addition, hemorrhage occurred in 10 patients from residual malformations between 4 and 34 months after treatment. Seizures and headaches were less severe in 63 percent of the 35 and 68 percent of the 40 patients, respectively, who had them initially.
Conclusions: Given the natural history of these inaccessible lesions and the high risks of surgery, we conclude that heavy-charged-particle radiation is an effective therapy for symptomatic, surgically inaccessible intracranial arteriovenous malformations. The current procedure has two disadvantages: a prolonged latency period before complete obliteration of the vascular lesion and a small risk of serious neurologic complications.