Conventional fractionated radiation therapy vs. radiosurgery for selected benign intracranial lesions (arteriovenous malformations, pituitary adenomas, and acoustic neuromas).

Abstract

Despite growing interest in radiosurgery, the precise role of radiosurgery relative to that of conventional fractionated external-beam radiation therapy is not fully clear. A critical review of the available data suggests that radiosurgery is both a safe and effective treatment for small arteriovenous malformations, pituitary adenomas and acoustic neuromas. For arteriovenous malformations, the effectiveness of radiosurgery is clearly reduced as the size of the malformation increases. Conventional external-beam radiation therapy is also an effective treatment for pituitary adenomas and acoustic neuromas, while the results for arteriovenous malformations are less encouraging. However, most arteriovenous malformations that have been treated with fractionated radiation therapy were large and received relatively low doses of radiation. One can speculate that high doses (> or = 50 Gy) of fractionated radiation therapy may be effective in the treatment of small arteriovenous malformations. Differences in the apparent effectiveness of radiosurgery and conventional fractionated radiation therapy are partly due to patient selection. A single fraction of approximately 20 Gy (a dose frequently used during radiosurgery) is probably 'biologically equivalent' to approximately 50 to 110 Gy of fractionated radiation therapy (at 2 Gy/fraction based on the linear quadratic model). In this regard, radiosurgery may be just a means of dose escalation. It remains to be shown that the possible benefit of radiosurgery could not be achieved by simply escalating the doses of fractionated radiation. Further clinical experience is needed to better define the role of radiosurgery. Randomized trials comparing conventional fractionated radiation vs. radiosurgery at approximately equal complication levels may be possible.