VOLUME CHANGES FOLLOWING GAMMA-KNIFE RADIOSURGERY OF INTRACRANIAL TUMORS

BACKGROUND The primary goal of radiosurgery for brain tumors is the pr evention of further growth, The purpose of this article is to evaluate temporal changes of tumor volume after Gamma Knife radiosurgery on in tracranial tumors. METHOD Some 137 patients with 148 intracranial tumo rs who were treated with Gamma Knife radiosurgery and underwent radiol ogical follow-up were reviewed, The tumors with high radiosensitivitie s to conventional external radiation were excluded. RESULT The median radiological follow-up period was 12 months (range 1.5-38 months), Vol ume decreased after radiosurgery in 15 of 45 meningiomas; 10 of 37 sch wannomas; 6 of 21 pituitary adenomas; 4 of 15 benign gliomas, includin g both of 2 subependymal giant cell astrocytomas; and 2 of 8 malignant gliomas. Some 87% of meningiomas and 60% of schwannomas whose volume had decreased began to shrink within 12 months and after 12 months, re spectively, Transitory increase in volume preceded shrinkage in 16.2% of schwannomas, 13.3% of benign gliomas, 4.8% of pituitary adenomas, a nd 2.2% of meningiomas. Marked shrinkage occurred in 17 of 19 metastat ic tumors and in all 3 neurocytomas shortly after radiosurgery. Of eig ht malignant gliomas, five began to grow 2-14 months (median = 5 month s) after radiosurgery. CONCLUSION Several points should be considered carefully while following up on patients after radiosurgery: the possi bility of transient volume increase, tumor-specific volume change patt erns, and the tumor-specific goals of radiosurgery. (C) 1997 by Elsevi er Science Inc.