Dose prescription and dose-volume effects in radiosurgery

The optimal use of radiosurgery as a treatment technique requires thorough planning, including careful fitting of the high-dose treatment volume to the target volume, and an understanding of the effects of high-dose single-fraction irradiation on both the target volume and the surrounding normal brain. The integrated logistic formula appears to be useful as an aid for predicting the risks of complications from radiosurgery, but greater understanding of the radiation tolerance for all the different areas of the brain (particularly the cranial nerves) is needed. The risk of developing MR imaging-defined changes after radiosurgery for AVMs was significantly related to predictions from the integrated logistic formula. The obliteration rate of AVMs after radiosurgery was volume dependent. Our assessment of the integrated logistic formula to date also indicates that it provides a reasonable guide for predicting complications in the radiosurgical treatment of meningiomas and in the treatment of solitary brain metastases using a combination of fractionated whole-brain irradiation and radiosurgery. The formula did not adequately predict complications in the treatment of AOVMs, however. In the treatment of acoustic tumors, the risks of injury to cranial nerves V, VII, and VIII clearly varied with treatment volume. Further data are needed to fully understand the therapeutic dose-response functions and volume effects for the obliteration of AVMs, the prevention of rebleeding from AOVMs, and growth arrest of meningiomas and acoustic neuromas.