Touboul E, Schlienger M
Service d'Oncologie-Radiothérapie, Hôpital Tenon (AP-HP), 4, rue de la Chine, 75020 Paris.
Neurochirurgie. 2001 May;47(2-3 Pt 2):212-20.
To attempt to analyze the basic effects of radiosurgery as applied to cerebral arteriovenous malformations.
We reviewed and discussed the previous issues of the international literature concerning radiobiological principles of radiosurgery of arteriovenous malformations.
The irradiated volume contained both a target volume consisting of abnormal vessels of the nidus often embedded within connective tissue stroma and the surrounding normal brain tissue. These were late-responding tissues after the radiation and sensitive tissues to high dose per fraction. There was not resistant hypoxic cell that could be killed efficiently with fractionated treatment. The therapeutic ratio between damage in the arteriovenous malformation nidus and late complications in the surrounding tissues was independent of fractionation. Furthermore, sterilization of all clonogenic cells in the target volume was not necessary to obtain complete obliteration of arteriovenous malformation. Consequently, there was nothing to be gained by a fractionated course relative to a stereotactic high single-dose irradiation for a small targeted volume (<=25 mm in diameter or<=4 200 mm(3)). The minimum target dose (Dmin) seemed to be the dosimetric independent predicting factor for complete obliteration. The Dmin-response relationship suggested a threshold dose of 5 Gy to 10 Gy and the better effects following Dmin from 20 Gy to 25 Gy. A Dmin above 25 Gy significantly increased the risk of serious late complications. The treated volume seemed to be the significant independent predicting dosimetric factor for developing persistent symptomatic sequelae. The optimum dose to deliver to obtain complete obliteration of an arteriovenous malformation was selected by balancing the expected obliteration rate for each dose with the corresponding risks from radiosurgery depending on size, location, shape and dose distribution.
Although the basic pathological process is still uncertain there is a strong rationale for stereotactic radiotherapy delivered in a high single-dose for small arteriovenous malformations.
试图分析立体定向放射外科治疗脑动静脉畸形的基本疗效。
回顾并讨论了此前国际文献中有关动静脉畸形立体定向放射外科治疗的放射生物学原理的问题。
照射体积既包括由常包埋于结缔组织基质中的畸形血管团组成的靶体积，也包括周围正常脑组织。这些是放疗后的晚反应组织，对每次高剂量敏感。不存在能用分次治疗有效杀灭的抗辐射乏氧细胞。动静脉畸形畸形血管团损伤与周围组织晚期并发症之间的治疗比与分次照射无关。此外，要使动静脉畸形完全闭塞，并不需要杀灭靶体积内所有的克隆源性细胞。因此，对于小的靶体积（直径<=25 mm或体积<=4200 mm³），相对于立体定向单次大剂量照射，分次疗程并无优势。最小靶剂量（Dmin）似乎是完全闭塞的剂量学独立预测因素。Dmin与反应的关系表明阈值剂量为5 Gy至10 Gy, Dmin在20 Gy至25 Gy时效果更佳。Dmin高于25 Gy会显著增加严重晚期并发症的风险。治疗体积似乎是发生持续性症状性后遗症的重要独立剂量学预测因素。通过平衡每个剂量的预期闭塞率与取决于大小、位置、形状和剂量分布的立体定向放射外科相应风险，选择使动静脉畸形完全闭塞的最佳照射剂量。
尽管基本病理过程仍不确定，但对于小的动静脉畸形采用单次大剂量立体定向放射治疗有充分的理论依据。
