Linac radiosurgery for cerebral arteriovenous malformations: Results in 169 patients

Purpose: To present the SALT group results using Linac radiosurgery (RS) fo r AVM in 169 evaluable patients treated from January 1990 thru December 199 3, Methods and Materials: Median age was 33 years (range 6-68 gears). Irradiat ion 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 minibe ams (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 pe ripheral dose was 25 Gy on the 60%-70% isodose (max dose 100%). Arteriograp hic 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 less than or equal to 4200 mm(3) vs. 51% for AVM > 4200 mm(3) (p = 0.02). The l argest nidus dimension ranged from 8 to 51 mm, median 22 mm, OR was 70% for nidus less than or equal to 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-isocenter s (p = 0.03), Peripheral doses (Pd) ranged from 15 to 28Gy, median 25 Gy, O R was 52% in patients receiving Pd less than or equal to 24.1 Gy or > 25.9 Gy and 70% for 25 GS' (NS). Peripheral isodoses ranged from 50%-90%, median 70%: OR was 67% for peripheral isodoses of 65% and 70% vs, 61% for periphe ral 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 less th an or equal to 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 1 6 Gy: OR was 69% for mLd > 17 Gy, vs. 59% for mLd I 16 Cy (p = 0.05), The m inimum lesion iodoses (mLi) ranged from 9%-65%, median 45%: OR was 71% for mLi > 40%, vs. 54% for mLi less than or equal to 40% (p = 0.05), The covera ge ratio (CR) ranged from 33%-100%, median 85%: OR was 68% for CR > 85% vs. 60% for CR less than or equal to 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, ab sence of previous embolization and mono isocentric-irradiation were indepen dent factors predicting obliteration. Complications were: recurrent hemorrh age, 4 patients (1 patient died); brain necrosis on MRI, 2 patients; subseq uent epilepsy, 1 patients; other subsequent neurologic deficits, 3 patients . Conclusion: Overall OR was 64% (48-96 months follow-up), After monovariate analysis higher ORs were associated with smaller volumes less than or equal to 4200 mm(3), smaller nidus size I 25 mm, absence of prior embolization, monoisocentric RS, higher values for mean and minimum lesion doses and comp liance to our protocol. Higher values for the peripheral dose and isodose t ended to give better results. Multivariate analysis showed that the absence of prior embolization and monoisocentric irradiation were independent fact ors predicting successfull irradiation. (C) 2000 Elsevier Science Inc.