[Radiosurgery by linear accelerators in the treatment of 84 arteriovenous malformations]

We have treated in 1990 and 1991, 84 arteriovenous malformations (AVMs) by radiosurgery. Irradiation was realized by 5 to 7 arcs with 15 MV X rays circular minibeams of a GE-CGR Saturne 43 Linac diameter, at 100 cm 6 to 20 mm; the Betti arm chair and the Talairach frame. The prescribed peripheral dose containing the nidus was 25 Gy corresponding to the 60-70% isodose range (100% was the maximum dose). For the irradiation planning we used the 'associated targets methodology' and the ARTEMIS-3D TPS, both of which have been developped in the radiotherapy departement of the Tenon hospital. Evaluation was performed in February 1995, the follow-up range was 38 to 62 months. In 1990, 46 cases were treated for cure and were all evaluable, whereas in 1991, among the 38 irradiated cases one patient was not evaluable because of lack of arteriographic control. Thus this series consisted in 84 evaluable cases. The overall obliteration rate was 65/84 (78%), partial obliteration was seen in 18/84 (21%) and no change in 1 case. According to AVM volume, obliteration rate was: AVMs < 4200 mm3: 82% (46/56). For lesions > 4200 mm3 it was 68% (19/28). In one isocenter irradiation, the obliteration rate was 42/47 (89%); whereas it was 23/37 (62%) in multi-isocenters treatments. The obliteration rate was better for not previously treated cases: 39/44 (89%) than for previously treated nidus (mostly embolisation) 65% (26/40). In 23 spheroid AVMs obliteration rate was 87% (20/23) in 43 ellipsoid AVMs the obliteration rate was 77% (33/43); and in irregular rounded nidus, it was 67% (12/18). The peripheral dose of 25 Gys has been used in 78 cases (93%), the obliteration rate was 63/78 (81%); in 6 other cases treated with 15-23.5 Gy, it was 2/6 (33%). We observed two recurrences of haemorrhage at 4 and 6 months after radiosurgery (recurrent haemorrhage rate 2/84 = 2.4%) with total neurological recovery in one of the two patients. One patient died of myocardial infarctus 11 months after radiosurgery (there was a partial obliteration of his AVM at 8 months after radiosurgery). There was no AVM related death. One patient developed an epilepsy.