[HYPOFRACTIONATED RADIOSURGERY FOR BENIGN BRAIN LESIONS--THE BEST OF ALL WORLDS]

Despite advances in neurosurgical technique, postoperative morbidity continues to taint open complete removal of many benign cranial base tumors (meningioma, pituitary adenomas, schwannomas). The incidence of temporary and permanent cranial nerve deficits is reported to be as high as 44% and 56% respectively, with postoperative mortality rates as high as 9%. As a consequence, many neurosurgeons choose to perform partial resections in order to preserve neurological functions. Progression rates after partial removal of a meningioma with no radiosurgery have been reported to be as high as 70%, compared to > 90% post-radiosurgical progression free survival rates. This resulted in a change of paradigms from an attempted radical resection to a combined neurosurgical-radiosurgical approach due to the high surgical morbidity the former entails. Radiosurgery has traditionally been used to treat lesions < 3.5-4 cm (or 14-16 cm³). Radiosurgery is thought to inactivate target cells regardless of their mitotic activity or inherent radio-sensitivity. When the distance between the tumor and anterior visual pathways is < 3 mm, radiosurgery is contraindicated because of the difficulty in delivering an effective dose to the tumor while maintaining a tolerable dose to the optic apparatus. Fractionated Radiosurgery (Temporal or spatial fractionation) may help overcome these limitations associated with larger volume target and dose fall-off. It should be considered in patients with sellar, parasellar or para-acoustic tumors involving major vasculature or when there is broad contact with the optic apparatus or cranial nerves. Fractionated radiosurgery offers a substantial reduction in radiation-related toxicity and with maintaining high tumor control rates.