Although-single fraction radiosurgery is of proven value for many types of intracranial disease, situations exist for which it cannot be used effectively. For example, consider an 8-year-old patient with residual craniopharyngioma after aggressive subtotal surgical resection. The residual tumor is densely adherent to the optic chiasm and hypothalamus. Single-fraction radiosurgery would therefore deliver the same dose of radiation to those structures as it would to the tumor capsule. A dose of >8Gy has an unacceptable risk of injuring the optic structures and is clearly too low to achieve long-term tumor control. An alternative is to deliver a conventionally fractionated course of external radiotherapy. This treatment has proven efficacy, but it also has substantial risk of causing long-term cognitive deficits. The ideal treatment would incorporate conventional fractionation to spare the critical neurologic structures, but it would use stereotactic targeting and dosimetry techniques to reduce the volume of normal brain exposed to potentially harmful doses of radiation; hence, stereotactic radiotherapy (SRT).
KeywordsMold Fractionation Immobilization Meningioma Chordoma
Unable to display preview. Download preview PDF.