Radiochirurgie des malformations artérioveineuses cérébrales : élaboration d’un algorithme de prescription

Abstract: Purpose: To study prognostic factors of obliteration and risk factors of brain radiation necrosis in order to propose an algorithm for radiosurgery prescription for cerebral arteriovenous malformations (cAVM). Material and methods: One hundred and seventy-nine patients were analysed. Radiosurgery delivered 6 or 10MV X-rays by arc therapy in 84% of cases, or by fixed field in 16% of cases using two different micro-multileaf collimators (micro-MLC). Follow-up consisted of screening radiation necrosis by MRI every 6 months, and assessing local control by arteriography every 2 years. Obliteration was defined as at least 95% reduction of cAVM volume. Cox proportional hazard model was used to evaluate the local control and the appearance of radiation necrosis over time. Results: Local control rate was 82.7% with the mean follow-up of 3.1 years (0.5–11). Significant prognostic factors were: simple nidus (RR=2.8, p <0.0001), number of embolizations before radiosurgery below4 (RR=2.9, p <0.0001), prescribed dose to the periphery of at least 18Gy (RR=2, p =0.0002), nidus volume below8cm3 (RR=1.9, p =0.0002), and number of table positions below six (RR=1.4, p =0.05). Radiation necrosis rate was 11.2% with a mean time to onset of 18 months. Significant predictive factors were: fixed field versus arc therapy (according to MLC RR=9.1, p <0.0001, and RR=15.1, p =0.01), age below 30 years (RR=2.5, p =0.04), depth of cAVM greater than or equal to 7cm (RR=7.6, p =0.008), and volume of brain tissue covered by the 12Gy isodose (V12Gy) of at least 11cm3 (RR=7.8, p =0.05). Conclusion: A radiosurgery prescription algorithm taking into account the prescribed dose to the periphery (≥ 18Gy) and reduction of V12Gy was elaborated from these data. [Copyright &y& Elsevier]