Linac radiosurgery for cerebral arteriovenous malformations: results in 169 patients

Purpose: To present the SALT group results using Linac radiosurgery (RS) for AVM in 169 evaluable patients treated from January 1990 thru December 1993. Methods and Materials: Median age was 33 years (range 6–68 years). Irradiation was the only treatment in 55% patients. Other treatment modalities had been used prior to RS in 45%: one or more embolizations in 36%, surgery in 6%, and embolization and surgery in 3% patients. Nidus were supratentorial in 94% patients, infratentorial in 6% patients. Circular 15 MV x-ray minibeams (6–20 mm) were delivered in coronal arcs by a GE-CGR Saturne 43 Linac. Patient set-up included a Betti arm-chair, a Talairach frame. Prescribed peripheral dose was 25 Gy on the 60%–70% isodose (max dose 100%). Arteriographic results were reassessed in December 1997 at 48 to 96 months follow-up. Results: The overall obliteration rate (OR) was 64% (108/169). AVM volumes ranged from 280 to 19,920 mm 3, median 2460 mm 3. OR was 70% for AVM ≤ 4200 mm 3 vs. 51% for AVM > 4200 mm 3 ( p = 0.02). The largest nidus dimension ranged from 8 to 51 mm, median 22 mm. OR was 70% for nidus ≤ 25 mm vs. 54% for nidus > 25 mm ( p = 0.04). OR was 71%, in the absence of embolization, vs. 54% for previously embolized nidus ( p = 0.03). OR was 71% for monocentric RS vs. 54% for multi-isocenters ( p = 0.03). Peripheral doses (Pd) ranged from 15 to 28Gy, median 25 Gy, OR was 52% in patients receiving Pd ≤ 24.1 Gy or > 25.9 Gy and 70% for 25 Gy (NS). Peripheral isodoses ranged from 50%–90%, median 70%: OR was 67% for peripheral isodoses of 65% and 70% vs. 61% for peripheral isodoses of 50%–60% (NS). The mean lesion doses (MLd) ranged from 14 to 36 Gy, median 29 Gy: OR was 72% for MLd > 28 Gy vs. 55% for values ≤ 28 Gy ( p = 0.02). The mean lesion isodoses (MLi) ranged from 53 to 90 Gy, median 79%: OR was 75% for MLi > 79% vs. 57% for lower values ( p = 0.03). The minimum lesion doses (mLd) ranged from 3.6 to 23, median 16 Gy: OR was 69% for mLd > 17 Gy, vs. 59% for mLd ≤ 16 Gy ( p = 0.05). The minimum lesion iodoses (mLi) ranged from 9%–65%, median 45%: OR was 71% for mLi > 40%, vs. 54% for mLi ≤ 40% ( p = 0.05). The coverage ratio (CR) ranged from 33%–100%, median 85%: OR was 68% for CR > 85% vs. 60% for CR ≤ 84% (NS). For patients treated according to our protocol, i.e., 24–26 Gy on the 60%–70% isodoses, OR was higher (68%) than for other patients (47%) ( p = 0.02). After multivariate analysis, absence of previous embolization and mono isocentric-irradiation