Stereotactic Radiosurgery: The Lyon Experience

From 10/1989 to 12/1992, 135 patients were treated, in Lyon, by Stereotactic Radiosurgery (RS) +/− External beam Radiotherapy (EBRT). Indications were AVMs or tumours that could not be cured by embolisation or/and surgery and are not larger than 30 to 35 mm. Lesions received 15 to 20 Gy (70% isodose) in one course. Among the 42 AVMs, only one rebled 6 months after RS and 9/15 had clinical improvement. Thirty-one had a radiological follow-up of 4 to 29 months after RS. Ten were totally obliterated, seven regressed more than 80% and six had a reduction of 50 to 80% of their AVM. Three grade 3 radio necrosis occurred for a cerebral trunk AVM and two large lesions. Three of the 15 treated meningiomas progressed after RS, 2 of them were controlled by conventional surgery. Four out of nine presenting symptoms had clinical improvement and, with a radiological follow-up of 4 to 24 months, 5 were stabilised and 6 regressed. Two grade three complications occurred for large lesions. The biological and radiological results of RS were good for the 42 treated pituitary adenomas but the high visual complication rate (12/42 with 8 grade 3) was too important and we stopped RS for these tumours except for small (less than 2cm) adenoma at some distance from the optic chiasma. The visual complications were related to the tumour volume, the distance between the adenoma and the visual tract and pre-existent visual alterations. The RS dose is now reduced for all lesions larger than 20 mm and a new fractionated technique will be developed to reduce the complication rate and to improve tumour control.