Immediate side effects of stereotactic radiotherapy and radiosurgery

Purpose: Despite increased utilization of fractionated stereotactic radiati on therapy (SRT) or stereotactic radiosurgery (SRS), the incidence and natu re of immediate side effects (ISE) associated with these treatment techniqu es are not well defined. We report immediate side effects from a series of 78 patients. Materials and Methods: Intracranial lesions in 78 adult patients were treat ed with SRT or SRS, using a dedicated linear accelerator. Those lesions inc luded 13 gliomas, 2 ependymomas, 19 metastatic tumors, 15 meningiomas, 12 a coustic neuromas, 4 pituitary adenomas, 1 optic neuroma, 1 chondrosarcoma, and 11 arteriovenous malformations (AVM). SRT was used in 51 and SRS in 27 patients. Mean target volume was 9.0 cc. Eleven patients received prior ext ernal-beam radiation therapy within 2 months before SRT/SRS. Any side effec ts occurring during and up to 2 weeks after the course of radiation were de fined as ISE and were graded as mild, moderate, or severe. The incidence of ISE and the significance of their association with several treatment and p retreatment variables were analyzed. Results: Overall, 28 (35%) of 78 patients experienced one or more ISE. Most of the ISE (87%) were mild, and consisted of nausea (in 5), dizziness/vert igo (in 5), seizures (in 6), and new persistent headaches (in 17). Two epis odes of worsening neurological deficit and 2 of orbital pain were graded as moderate. Two patients experienced severe ISE, requiring hospitalization ( 1 seizure and 1 worsening neurological deficit). ISE in 6 cases prompted co mputerized tomography of the brain, which revealed increased perilesional e dema in 3 cases. The incidence of ISE by diagnosis was as follows: 46% (6 o f 13) for gliomas, 50% (6 of 12) for acoustic neuromas, 36% (4 of 11) for A VM, 33% (5 of 15) for meningiomas, and 21% (4 of 19) for metastases. A high er incidence of dizziness/vertigo (4 of 12 = 33%) was seen among acoustic n euroma patients than among other patients (n < 0.01). There was no signific ant association of dizziness/vertigo with either a higher average and maxim um brainstem dose (p = 0.74 and 0.09, respectively) or with 2-Gy equivalent s of the average and maximum brainstem doses (p = 0.28 and 0.09, respective ly). Higher RT dose to the margin and higher maximum RT dose were associate d with a higher incidence of ISE (p = 0.05 and 0.01, respectively). However , when RT dose to the margin was converted to a 2-Gy dose-equivalent, it lo st its significance as predictor of ISE (p = 0.51). Recent conventional ext ernal-beam radiation therapy, target volume, number of isocenters, collimat or size, dose inhomogeneity, prescription isodose, pretreatment edema, dose of prior radiation, fraction size (2.0-7.0 Gy with SRT and 13.0-21.0 Gy wi th SRS), fractionation schedule, and dose to brainstem were not significant ly associated with ISE. ISE occurred in 26% (8) of 31 patients taking corti costeroids prior to SRT/SRS and in 20 (42%) of 47 patients not taking them (p = 0.15). Conclusion: ISE occur in one third of patients treated with SRT and SRS and are usually mild or moderate and self-limited. Dizziness/vertigo are commo n and unique for patients with acoustic neuromas and are not associated wit h higher brainstem doses. We are unable to detect a relationship between IS E and higher margin or maximum RT doses. No specific conclusion can be draw n with regard to the effect of corticosteroids, used prior to SRS/SRT, on t he occurrence of ISE. (C) 1999 Elsevier Science Inc.