HIGH-PRECISION EXTERNAL RADIOTHERAPY OF BRAIN-TUMORS

The combination of patient fixation and localization systems and compu ter-assisted three-dimensional treatment planning. has led to sophisti cated high-precision external irradiation treatment techniques. Radios urgery was first described 1951 by Leksell, but not realized for routi ne clinical use until 1971 with the design of the Gamma Knife system. In the 1980s this method was transferred to modern linear accelerators . The further development led from stereotactic single-dose convergent beam irradiation to fractionated stereotactically guided conformation radiotherapy. Steep decrease of dose allows the selective destruction of small intracranial lesions, while the surrounding brain tissue is optimally protected. Radiosurgery of arteriovenous malformations achie ved complete obliteration rates from 71% up to 82% with complication r ates df 3%. Local tumor control rates between 85% and 95% were obtaine d in the treatment of acoustic neurinoma and brain metastases. One of the most important technical advances in radiooncology is the stereota ctic fractionated 3D conformation radiotherapy. It allows escalation o f radiation dose to the tumor volume without increasing dose to the su rrounding healthy tissue. There is a potential benefit in improving lo cal tumor control and cure rates. Therefore, are have selected treatme nt results of tumors of the cranial base, optic nerve sheath meningiom as, and high-grade gliomas. As conclusion the pros and cons of each tr eatment method and the clinical results are discussed. In addition, fu ndamental aspects of radiobiology are described. For high-precision ra diotherapy and radiosurgery a multidisciplinary team work is an indisp ensable prerequisite. This requires a close cooperation between neuros urgeons, neuroradiologists, radiooncologists, and biophysicists.