Faculty Bibliography

Stereotactic radiosurgery is effective in controlling brain metastasis at presentation and those that recur after radiotherapy. It is the treatment of choice for most patients with small solitary brain metastasis by virtue of its low morbidity, high-effectiveness, and cost.

PURPOSE: Between June 1988 and June 1994. 38 hemangioblastomas were treated with stereotactic radiosurgery (SR) at three SR centers to evaluate the efficacy and potential toxicity of this therapeutic modality as an adjuvant or alternative treatment to surgical resection. METHODS AND MATERIALS: SR was performed using either a 201-cobalt source unit or a dedicated SR linear accelerator. Of the 18 primary tumors treated, 16 had no prior history of surgical resection and were treated definitively with SR and two primary lesions were subtotally resected and subsequently treated with SR. Twenty lesions were treated with SR after prior surgical failure (17 tumors) or failure after prior surgery and conventional radiotherapy (three tumors). Eight patients were treated with SR for multifocal disease (total, 24 known tumors). SR tumor volumes measured 0.05 to 12 cc (median: 0.97 cc). Minimum tumor doses ranged from 12 to 20 Gy (median: 15.5 Gy). RESULTS: Median follow-up from the time of SR was 24.5 months (range: 6-77 months). The 2-year actuarial over-all survival was 88 +/- 15% (95% confidence interval). Two-year actuarial freedom from progression was 86 +/- 12% (95% confidence interval). The median tumor volume of the lesions that failed to be controlled by SR was 7.85 cc (range: 3.20-10.53 cc) compared to 0.67 cc (range: 0.05-12 cc) for controlled lesions (p - 0.0023). The lesions that failed to be controlled by SR received a median minimum tumor dose of 14 Gy (range: 13-17 Gy) compared to 16 Gy (range: 12-20 Gy) for controlled lesions (p = 0.0239). Seventy-eight percent of the surviving patients remained neurologically stable or clinically improved. There were no significant permanent complications directly attributable to SR. CONCLUSIONS: This report documents the largest experience in the literature of the use of SR in the treatment of hemangioblastoma. We conclude that SR: (a) controls the majority of primary and recurrent hemangioblastomas; (b) offers the ability to treat multiple lesions in a single treatment session, which is particularly important for patients with Von Hippel-Lindau Syndrome; and that (c) better control rates are associated with higher doses and smaller tumor volumes.

A multiinstitutional study was conducted to evaluate the technique, dose-selection parameters, and results of gamma knife stereotactic radiosurgery in the management of trigeminal neuralgia. Fifty patients at five centers underwent radio-surgery performed with a single 4-mm isocenter targeted at the nerve root entry zone. Thirty-two patients had undergone prior surgery, and the mean number of procedures that had been performed was 2.8 (range 1-7). The target dose of the radiosurgery used in the current study varied from 60 to 90 Gy. The median follow-up period after radiosurgery was 18 months (range 11-36 months). Twenty-nine patients (58%) responded with excellent control (pain free), 18 (36%) obtained good control (50%-90% relief), and three (6%) experienced treatment failure. The median time to pain relief was 1 month (range 1 day-6.7 months). Responses remained consistent for up to 3 years postradiosurgery in all cases except three (6%) in which the patients had pain recurrence at 5, 7, and 10 months. At 2 years, 54% of patients were pain free and 88% had 50% to 100% relief. A maximum radiosurgical dose of 70 Gy or greater was associated with a significantly greater chance of complete pain relief (72% vs. 9%, p = 0.0003). Three patients (6%) developed increased facial paresthesia after radiosurgery, which resolved totally in one case and improved in another. No patient developed other deficits or deafferentation pain. The proximal trigeminal nerve and root entry zone, which is well defined on magnetic resonance imaging, is an appropriate anatomical target for radiosurgery. Radiosurgery using the gamma unit is an additional effective surgical approach for the management of medically or surgically refractory trigeminal neuralgia. A longer-term follow-up review is warranted.

To identify histological changes and effects on survival in rats harboring C6 gliomas, the authors compared radiosurgery to different fractionated radiation therapy regimens including doses of calculated biological equivalence. Rats were randomized to control (54 animals) or treatment groups after implantation of C6 glioma cells into the right frontal brain region. At 14 days, treated rats underwent stereotactic radiosurgery (35 Gy to tumor margin; 22 animals), whole-brain radiation therapy (WBRT) (20 Gy in five fractions; 18 animals), radiosurgery plus WBRT (13 animals), hemibrain radiation therapy (85 Gy in 10 fractions; 16 animals) or single-fraction hemibrain irradiation (35 Gy; 10 animals). When compared to the control group (median survival 22 days), prolonged survival was identified after radiosurgery (p < 0.0001), radiosurgery plus WBRT (p < 0.0001), WBRT alone (p = 0.0002), hemibrain radiation therapy to 85 Gy (p < 0.0001), and 35-Gy hemibrain single-fraction irradiation (p = 0.004). Compared to the control group (mean tumor diameter, 6.8 mm), the tumor size was reduced in all treatment groups except WBRT alone. Reduced tumor cell density was exhibited in rats that underwent radiosurgery (p = 0.006) and radiosurgery plus WBRT (p = 0.009) when compared with rats in the control group, a finding not observed after any fractionated regimen. Increased intratumoral edema was identified after radiosurgery (p = 0.03) and combined treatment (p = 0.05), but not after fractionated radiation therapy or 35-Gy single-fraction hemibrain irradiation. In this animal model, the addition of radiosurgery significantly increased tumor cytotoxicity, potentially at the expense of radiation effects to regional brain. We found no difference in survival benefit or tumor diameter in animals that underwent radiosurgery compared to the calculated biologically equivalent regimen of 10-fraction radiation therapy to 85 Gy. The histological responses after radiosurgery were generally greater than those achieved with biologically equivalent doses of fractionated radiation therapy.

This article reviews the authors' experience with image-guided surgery for brain metastases and discusses specifically the impact of the frameless viewing wand system on standard craniotomy techniques for this disorder. Topics discussed include patient selection, interactive image-guided neurosurgical resection of brain metastases, and other image-guided neurosurgical systems.

We evaluated the role of stereotactic radiosurgery (SRS) in 25 children with surgically incurable brain tumors of glial origin. Histological diagnoses were obtained at the time of craniotomy and attempted removal (n = 20) or by stereotactic biopsy (n = 5). Thirteen children had tumors with benign histological characteristics (pilocytic and low-grade astrocytomas), whereas 12 children had tumors with malignant characteristic (malignant astrocytomas and ependymomas). Eleven (10 with malignant tumors) of the 25 children had received fractionated irradiation before SRS. Radiosurgical doses (range to margin, 11-20 Gy) were calculated on the basis of tumor volume and location, with consideration given to prior radiation dose. Follow-up for the 13 children with benign tumors ranged from 6 to 48 months (median, 21 mo). Eleven of the 13 children with "benign" glial neoplasms had tumor control with SRS alone (no evidence of tumor, n = 4; decreased tumor, n = 5; and unchanged tumor, n = 2), and all 13 remain alive. Five children with malignant tumors are alive at 12, 45, 50, 72, and 72 months after radiosurgery. The other seven children with malignant tumors are dead, with a median survival of 6 months after radiosurgery. Three of 12 children with malignant glial neoplasms had tumor control after SRS. Two of these three children received fractionated irradiation as an adjunct to SRS. Complications occurring in four children were transient, associated with peritumoral edema, and responsive to oral glucocorticoids. There was no relationship between tumor volume and local control after radiosurgery. Radiosurgery alone is a safe and effective treatment modality for unresectable benign gliomas of childhood. Radiosurgery may have a role in the adjuvant management of unresectable malignant glial neoplasms of childhood if other therapies (irradiation or chemotherapy) are available.

To analyze the effect of stereotactic radiosurgery on the hemorrhage rate of arteriovenous malformations (AVMs), we reviewed the clinical and angiographic characteristics of 315 patients with AVMs before and after radiosurgery. One hundred ninety-six patients sustained 263 bleeds in 10,939 patient-years before radiosurgery, for an annual nonfatal hemorrhage rate of 2.4%. Clinical follow-up after radiosurgery was available in 312 patients (mean, 47 +/- 20 mo); follow-up > or = 24 months was obtained in 295 patients (94%). Twenty-one patients had AVM bleeds at a median of 8 months (range, 1-60 mo) after radiosurgery. Two additional patients had three aneurysmal bleeds (at 5, 27, and 32 mo, respectively) for a 7.4% total risk of hemorrhage per patient. The actuarial hemorrhage rate until AVM obliteration was 4.8% per year (95% confidence interval, 2.4-7.0%) during the first 2 years after radiosurgery and 5.0% per year (95% confidence interval, 2.3-7.3%) for the third to fifth years after radiosurgery. Multivariate analysis of clinical and angiographic factors demonstrated that the presence of an unsecured proximal aneurysm was associated with an increased risk of postradiosurgical hemorrhage (relative risk, 4.56; 95% confidence interval, 1.77-11.70%; P < 0.001). No AVM hemorrhages were observed after radiosurgery in seven patients with intranidal aneurysms. No protective effect against hemorrhage was observed in patients who received an "optimal" radiation dose (> or = 25 Gy to the AVM margin) compared with patients who received < 25 Gy to the AVM margin (P = 0.36). No patient suffered a hemorrhage after angiography had confirmed complete obliteration (n = 140) or suffered from an early draining vein without residual nidus (n = 19). Stereotactic radiosurgery was not associated with a significant change in the hemorrhage rate of AVMs during the latency interval before obliteration. No protective benefit was conferred on patients who had incomplete nidus obliteration in early (< 60 mo) follow-up after radiosurgery. AVM patients with unsecured proximal aneurysms should have aneurysms obliterated either before radiosurgery or at the time of surgical resection of their AVMs.

BACKGROUND: Treatment options for head and neck cancers that recur at the cranial base are limited. METHODS: Twelve patients with head and neck cancers recurrent after resection and fractionated radiotherapy (n = 11) at the cranial base had stereotactic radiosurgery using the gamma unit. The median dose to the tumor margin was 16 Gy. Imaging follow-up varied from 3 to 17 months; the longest clinical follow-up was at 35 months. RESULTS: Three of 8 tumors studied by postradiosurgery imaging remained unchanged in size, 3 decreased, and 2 were no longer visible. There was no morbidity or worsening of symptoms after radiosurgery. Four patients died between 4 and 8 months and did not have postradiosurgery imaging performed. Mean survival after radiosurgery was 10.5 months, with 7 patients (58%) still living. CONCLUSIONS: Radiosurgery proved safe and effective in providing local control for recurrent cranial base cancers arising from the extracranial head and neck. Radiosurgery should be considered for those patients who have failed prior fractionated radiation or surgical resection, those who have tumors in high-risk cranial locations, or those who are poor medical candidates. Although this study shows its potential adjuvant role, longer follow-up and increased clinical experience will be necessary to evaluate the overall role of radiosurgery in head and neck cancer.

Arteriovenous malformations (AVMs) that are located within the postgeniculate optic radiations or striate cortex are difficult to resect without creating postoperative visual defects. To reduce the risk of an AVM hemorrhage and to enhance the possibility of preserving visual function, the authors performed stereotactic radiosurgery in 34 patients with newly diagnosed or residual AVMs of the visual pathways. The mean AVM volume was 4.7 ml, and the average radiation dose to the AVM margin was 21 Gy. The median follow up was 47 months (range 16-83 months). Two (6%) of 34 patients had documented new visual field defects (central scotoma in one, and partial hemianopsia in one) after single-stage radiosurgery, but no patient developed a new permanent homonymous hemianopsia. Angiography was performed in all patients at a median of 26 months after radiosurgery: 22 (65%) had complete obliteration, 10 (29%) had a significant decrease in AVM volume, one (3%) had only a persistent early draining vein without residual nidus, and one (3%) had no change in the AVM. Thirteen (81%) of 16 patients with AVMs less of than 4 ml had complete obliteration. Five patients had second-stage stereotactic radiosurgery after angiography revealed a persistent AVM nidus; two patients eligible for follow-up angiography had complete obliteration, thereby increasing the overall series obliteration rate to 71%. The calculated annual risk of AVM bleeding (before radiographic evidence of obliteration) was 2.4%. No patient bled after angiographically confirmed obliteration. In most patients stereotactic radiosurgery obliterates visual pathway AVMs and also preserves preoperative visual function. Multimodality management (embolization, microsurgery, or staged radiosurgery) enhances AVM obliteration and visual preservation rates.