Faculty Bibliography

BACKGROUND: Stereotactic radiosurgery (SRS) to the resection bed of a brain metastasis is an important treatment option. OBJECTIVE: To identify factors associated with tumor progression after SRS of the resection bed of a brain metastasis and to evaluate patterns of failure for patients who eventually had tumor progression. METHODS: We performed a retrospective analysis of 120 patients who underwent tumor bed radiosurgery after an initial gross total resection. The mean imaging follow-up time was 55 weeks. The median margin dose was 16 Gy. Forty-seven patients (39.2%) underwent whole-brain radiation therapy before or shortly after SRS. RESULTS: Local tumor control was achieved in 103 patients (85.8%). Progression-free survival was 96% at 6 months, 87% at 12 months, and 74% at 24 months. Recurrence most commonly occurred deep in the cavity (65%) outside the planned treatment volume (PTV) margin (53%). PTV, cavity diameter, and a margin dose < 16 Gy significantly correlated with local failure. For patients with PTVs >/= 8.0 cm, local progression-free survival declined to 93% at 6 months, 83% at 12 months, and 65% at 24 months. Development or progression of distant metastases occurred in 40% of patients. Whole-brain radiation therapy was not associated with improved local control. CONCLUSION: Resection bed SRS for brain metastases provided excellent local control. The cavity PTV is predictive of tumor control. Because failure usually occurs outside the PTV, inclusion of a judicious 2- to 3-mm margin beyond the area of postoperative enhancement may be prudent. ABBREVIATIONS: ARE, adverse radiation effectPTV, planned treatment volumeSRS, stereotactic radiosurgeryWBRT, whole-brain radiation therapy.

Intrinsic meningiomas of the superior sagittal sinus pose a significant technical challenge, particularly in the posterior two-thirds of the sinus. Resection is curative but frequently is not possible because of the involvement of critical vascular structures. Here, the authors present the case of a 49-year-old woman with a recurrent meningioma located exclusively in the posterior two-thirds of the sagittal sinus. The patient was treated with a margin dose of 12 Gy and a maximum dose of 24 Gy to the length of the tumor, which measured 16 cm. Five years after treatment, the tumor remains stable and the patient is symptom free. This case demonstrates the unique role that stereotactic radiosurgery can play in the management of meningiomas that are surgically unresectable and have no accepted form of treatment. To the authors' knowledge, 16 cm also represents the longest segment of tumor treated using stereotactic radiosurgery.

To retrospectively evaluate the clinical benefit and imaging response of bevacizumab when used to treat refractory adverse radiation effects (ARE) after stereotactic radiosurgery. Twenty-nine patients with brain tumors or vascular malformations developed clinical and/or imaging evidence of ARE after SRS and were treated using bevacizumab. Patients received an average dose of 7.4 mg/kg over a mean of 5.7 weeks at a median of 16 months following SRS. Initial diagnosis, SRS dose, bevacizumab treatment protocols, magnetic resonance imaging T2/FLAIR and T1 paramagnetic contrast enhanced edema volumes were compared before and after bevacizumab administration. Ninety percent (18/20) with clinically symptomatic ARE had neurological improvement after bevacizumab therapy. Twenty-six patients had a decrease of 62 % of T2/FLAIR volumes and a 50 % decrease in magnetic resonance imaging intravenous contrast enhancement volumes. Two patients showed progression of the T2/FLAIR and contrast enhancement volumes. One patient had progression of post-Gd-enhancement but regression of T2/FLAIR volume. Symptoms recurred in 11 of the 20 patients after discontinuing therapy. Patients who experienced a return of enhancement received a lower marginal dose during SRS. Our experience provides additional evidence that bevacizumab reduces both symptoms and reactive imaging changes in patients with ARE. After SRS, refractory ARE unresponsive to initial corticosteroids or other agents may benefit from a bevacizumab trial. The necessary duration and optimum dose of therapy is unknown and provides a further impetus to conduct a prospective trial.

Stereotactic radiosurgery is used for many indications. In functional neurosurgery, it is used to modulate the function of axons, neurons, and related brain circuits. In this article, indications, current techniques, and outcomes are discussed.

Object The authors sought to better define the clinical response of patients who underwent stereotactic radiosurgery (SRS) for brain metastases located in the region of the motor cortex. Methods A retrospective analysis was performed in 2026 patients with brain metastasis who underwent SRS with the Gamma Knife between 2002 and 2012, and multiple factors that affect motor function before and after SRS were evaluated. Ninety-four patients with tumors >/= 1.5 cm in diameter located in or adjacent to the motor strip were identified, including 2 patients with bilateral motor strip metastases. Results Motor function improved after SRS in 30 (31%) of 96 cases, remained stable in 48 (50%), and worsened over time in 18 (19%) instances. Forty-seven patients had no motor weakness prior to radiosurgery; 10 (22%) developed new Grade 3/5-4/5 weakness. Thirty (68%) of 44 patients with >/= 3/5 pre-SRS weakness improved, 6 (14%) remained stable, and 8 (18%) worsened. Three of 5 patients with < 3/5 pre-SRS motor function improved. Motor deficits prior to SRS did not correlate with a worse outcome; however, worse outcomes were associated with larger tumor volumes. The median tumor volume in patients whose function improved or remained stable was 5.3 cm(3), but it was 9.2 cm(3) in patients who worsened (p < 0.05). Tumor volumes > 9 cm(3) were associated with a higher risk of worsening motor function. Adverse radiation effects occurred in 5 patients. Conclusions Most intact patients with brain metastases in or adjacent to motor cortex maintained neurological function after SRS, and most patients with symptomatic motor weakness remained stable or improved. Larger tumor volumes were associated with less satisfactory outcomes.

PURPOSE: Gamma knife radiosurgery (RS) may be an alternative to open surgery for mesial temporal lobe epilepsy (MTLE), but morbidities and the anticonvulsant mechanisms of RS are unclear. Examination of visual field defects (VFDs) after RS may provide evidence of the extent of a postoperative fixed lesion. VFDs occur in 52-100% of patients following open surgery for MTLE. METHODS: This multicenter prospective trial of RS enrolled patients with unilateral hippocampal sclerosis and concordant video-electroencephalography (EEG) findings. Patients were randomized to low (20 Gy) or high (24 Gy) doses delivered to the amygdala, hippocampal head, and parahippocampal gyrus. Postoperative perimetry were obtained at 24 months after RS. Visual field defect ratios (VFDRs) were calculated to quantify the degree of VFDs. Results were contrasted with age, RS dose and 50% isodose volume, peak volume of radiation-induced change at the surgical target, quality of life measurements, and seizure remission. KEY FINDINGS: No patients reported visual changes and no patients had abnormal bedside visual field examinations. Fifteen (62.5%) of 24 patients had postoperative VFDs, all homonymous superior quadrantanopsias. None of the VFDs were consistent with injury to the optic nerve or chiasm. Clinical diagnosis of VFDs correlated significantly with VFDRs (p = 0.0005). Patients with seizure remission had smaller (more severe) VFDRs (p = 0.04). No other variables had significant correlations. SIGNIFICANCE: VFDs appeared after RS in proportions similar to historical comparisons from open surgery for MTLE. The nature of VFDs was consistent with lesions of the optic radiations. The findings support the hypothesis that the mechanism of RS involves some degree of tissue damage and is not confined entirely to functional changes in neuromodulation.