Hypofractionated stereotactic radiotherapy for large or involving critical organs cerebral arteriovenous malformations
Background. Treatment of large arteriovenous malformations (AVMs) or AVMs involving eloquent regions of the brain remains a challenge. For inoperable lesions, observation, volume-staged radiosurgery or hypofractionated stereotactic radiotherapy (HFSRT) are proposed.
Objective. The aim of our study was to assess the safety and efficiency of HFSRT for large AVMs located in eloquent areas of the brain.
Methods. Analysis of records of 49 patients irradiated for cerebral AVMs with mean dose of 19.9 Gy (12 - 28 Gy) delivered in 2-4 fractions with planned gap (at least one week) between fractions. Actuarial obliteration rates and annual bleeding hazard were calculated using Kaplan-Meier survival analysis and life tables.
Results. Annual bleeding hazard rates were 4.5% and 1.6% after one and two years of follow-up, respectively. Actuarial total obliteration rates were 7%, 11%, and 21% and total response rate (total and partial obliterations) 22%, 41%, and 55% after one, two and three years of follow-up, respectively . There was a trend towards larger total obliteration rate in patients irradiated with fraction dose >= 8 Gy and total dose > 21 Gy for lesions of volume <= 8.18 ccm which was not observed in case of partial obliterations.
Conclusions. HFSRT results with relatively low obliteration rate but is not associated with significant risk of permanent neurological deficits if total and fraction dose are adjusted to size and location of the lesion. Predictive factors for total and partial obliterations can be different; this observation however is not firmly supported and requires further studies.