CLINICAL AND RADIOLOGICAL EVALUATION OF LONG-TERM RESULTS OF STEREOTAXIC PROTON-BEAM RADIOSURGERY IN PATIENTS WITH CEREBRAL ARTERIOVENOUS-MALFORMATIONS

Within a period of nearly 10 years, from October, 1980, to May, 1990, a total of 68 patients with a cerebral arteriovenous malformation (AVM ) were referred to a radiosurgical center in the United States for ste reotactic Bragg peak proton beam therapy. Radiosurgery was chosen as a n alternative treatment, either because the AVM was considered to be o f high surgical risk due to its size and/or location, or because the p atient refused surgery. In 63 patients (92.6%), complete clinical and radiological follow-up examinations were available. Clinical and radio logical longterm results were correlated to size and to the Spetzler-M artin scale of the AVM. With increasing size or higher grade on the Sp etzler-Martin scale, the clinical results of proton beam therapy becam e progressively worse. Of 37 patients with an AVM between 3 and 6 cm i n diameter, only one-third showed amelioration of their clinical sympt oms, and two-thirds remained the same or even deteriorated after radia tion treatment. The same results apply to patients with very large AVM 's, of whom only one-third profited from proton beam therapy. Although 85.7% of the patients in Spetzler-Martin Grades I and II showed posti rradiation amelioration of their clinical symptoms, this compares to o nly 54.2% of the patients in Grade III, and only 24% in Grade IV. In r egard to the radiological results of proton beam therapy, complete obl iteration during long-term observation was only detectable in 10 patie nts or 15.9%, which is less than one-sixth of the whole group of 63 pa tients. All of these obliterated AVM's were smaller than 3 cm. Almost 85% of the patients treated using stereotactic proton beam therapy did not show any angiographic change in the radiological appearance of th eir AVM. The results reported here indicate that radiosurgery using st ereotactic proton beam therapy is ineffective for the treatment of med ium- or large-sized AVM's and should not be recommended for patients h arboring an AVM larger than 3 cm. If proton beam treatment is contempl ated, it should be restricted to AVM's that are less than 3 cm in size and whose location makes them easily accessible only for proton beam therapy.