Stereotactic radiosurgery for brain metastases from breast cancer

BACKGROUND

Stereotactic radiosurgery is an alternative to resection or to radiotherapy alone for patients with brain metastases. Outcomes after radiosurgery for patients with brain metastases specifically from breast cancer have not been defined.

METHODS

We retrospectively studied survival and tumor control for all patients with brain metastases from breast cancer who underwent gamma knife stereotactic radiosurgery at the University of Pittsburgh. Univariate and multivariate analyses were used to determine which prognostic factors significantly affected survival.

RESULTS

Thirty patients underwent radiosurgery between 1990 and 1997. A total of 58 metastases were treated. The median length of survival for all patients was 13 months from radiosurgery and 18 months from diagnosis of brain metastases. The tumor control rate on follow-up imaging was 93%. On multivariate analysis, the only factor that correlated with longer survival was the absence of multiple brain metastases. Age, presence of systemic disease, previous whole brain radiation, location, and total tumor volume did not significantly affect survival. Four patients had tumors with evidence of radiation-induced edema after radiosurgery but did not require resection. Two patients underwent delayed resection for tumor growth after radiosurgery.

CONCLUSIONS

Stereotactic radiosurgery is an effective treatment for brain metastases from breast cancer and is associated with a low complication rate.

Successful management of sellar and suprasellar arachnoid cysts with stereotactic intracavitary irradiation: an expanded report of four cases

OBJECTIVE

Sellar and suprasellar arachnoid cysts may be asymptomatic or may cause headache, optic nerve compression, endocrine dysfunction, or hydrocephalus. We propose a minimally invasive treatment strategy when intervention is indicated.

METHODS

Four patients with sellar and suprasellar arachnoid cysts presented with headache, visual compromise, and endocrine dysfunction. Two of the four patients previously had undergone unsuccessful surgical intervention. The imaging studies of two patients were diagnostic of an arachnoid cyst.

RESULTS

All four patients underwent stereotactic intracavitary radiation with cyst regression and symptomatic improvement. In each patient, the optic chiasm was decompressed successfully. There were no complications from the procedure.

CONCLUSION

Stereotactic intracavitary irradiation of arachnoid cysts proved to be safe and effective. The procedure obviated the need for open cyst fenestration or shunting.

Histological effects of trigeminal nerve radiosurgery in a primate model: implications for trigeminal neuralgia radiosurgery

OBJECTIVE

Stereotactic radiosurgical treatment of the proximal trigeminal nerve is used to relieve the pain of trigeminal neuralgia. The mechanism of the radiosurgical effect is not understood.

METHODS

Two adult baboons underwent stereotactic magnetic resonance imaging-guided radiosurgery, using a gamma knife. A single 4-mm isocenter was targeted to each proximal trigeminal nerve, just anterior to the pons, to deliver a maximal dose of 80 or 100 Gy (total of four nerves). A nonirradiated baboon brain and nerves served as control specimens. Six months after treatment, magnetic resonance imaging was again performed and the brains and nerves were studied using light and electron microscopy.

RESULTS

Magnetic resonance imaging indicated a 4-mm-diameter area of contrast enhancement at the target site in each nerve. All irradiated nerves exhibited axonal degeneration and mild edema at the target, with remnants of some myelinated axons. Large and small myelinated and unmyelinated fibers were affected. No inflammation was observed. Nerve necrosis was identified after 100-Gy treatment. The trigeminal ganglion appeared normal.

CONCLUSION

Radiosurgery at 80 Gy causes focal axonal degeneration of the trigeminal nerve. At higher doses, partial nerve necrosis is observed. We think that these effects influence the physiological features of trigeminal neuralgia.

Development of a model to predict permanent symptomatic postradiosurgery injury for arteriovenous malformation patients. Arteriovenous Malformation Radiosurgery Study Group

PURPOSE

To better predict permanent complications from arteriovenous malformation (AVM) radiosurgery.

METHODS AND MATERIALS

Data from 85 AVM patients who developed symptomatic complications following gamma knife radiosurgery and 337 control patients with no complications were evaluated as part of a multi-institutional study. Of the 85 patients with complications, 38 patients were classified as having permanent symptomatic sequelae (necrosis). AVM marginal doses varied from 10-35 Gy and treatment volumes from 0.26-47.9 cc. Median follow-up for patients without complications was 45 months (range: 24-92).

RESULTS

Multivariate analysis of the effects of AVM location and the volume of tissue receiving 12 Gy or more (12-Gy-Volume) allowed construction of a significant postradiosurgery injury expression (SPIE) score. AVM locations in order of increasing risk and SPIE score (from 0-10) were: frontal, temporal, intraventricular, parietal, cerebellar, corpus callosum, occipital, medulla, thalamus, basal ganglia, and pons/midbrain. The final statistical model predicts risks of permanent symptomatic sequelae from SPIE scores and 12-Gy-Volumes. Prior hemorrhage, marginal dose, and Marginal-12-Gy-Volume (target volume excluded) did not significantly improve the risk-prediction model for permanent sequelae (p >/= 0.39).

CONCLUSION

The risks of developing permanent symptomatic sequelae from AVM radiosurgery vary dramatically with location and, to a lesser extent, volume. These risks can be predicted according to the SPIE location-risk score and the 12-Gy-Volume.

Radiosurgery: where we were, are, and may be in the third millennium

Radiosurgery will celebrate its Golden Jubilee in the year 2001. More than 100,000 patients throughout the world have undergone radiosurgery since Lars Leksell first described the technique in 1951. Rapid developments in neuroimaging and even robotic technology in the past decade have contributed to improved outcomes and wider applications for radiosurgery. A variety of different radiosurgical techniques have been developed in the past two decades. Numerous studies have examined the benefits and risks of radiosurgery performed with various devices. The long-term results of radiosurgery are now available, and these results have established radiosurgery as an effective noninvasive treatment method for intracranial vascular malformations and many tumors. Additional applications of radiosurgery for the treatment of malignant tumors and functional disorders are being assessed. Radiosurgery is an impressive combination of minimally invasive technologies administered by a multidisciplinary team of surgeons, oncologists, medical physicists, and engineers.

Effects of stereotactic radiosurgery on an animal model of hippocampal epilepsy

OBJECTIVE

Stereotactic radiosurgery has been shown in small clinical series to reduce or abolish seizures in patients with lesion-related or idiopathic epilepsy. The radiation dose necessary to eliminate epileptogenesis is unknown, and the histological and metabolic effects of radiosurgery remain undefined. We hypothesized that in a rat model of kainic acid-induced hippocampal epilepsy, radiosurgery could provide a significant reduction in seizure frequency while limiting biochemical and structural histological damage to the brain.

METHODS

Kainic acid (8 g) was injected into the rat hippocampus using stereotactic targeting. Focal seizures so generated were identified with scalp and depth electroencephalography (EEG). Epileptic rats were randomized to a control group (n = 20) and to radiosurgery groups in which maximum doses of 20, 40, 60, or 100 Gy (8-9 animals per group) were administered. Over a 42-day period, seizure frequency was determined by direct observation for 8 hours per week. Scalp EEG was performed weekly in all animals. Magnetic resonance imaging (MRI) studies (T1- and T2-weighted water-proton and quantitative sodium images) were obtained on Days 7, 21, and 42.

RESULTS

As compared with the control group, treated animals showed significant reductions in the number of seizures during each successive week after 20-Gy radiosurgery (P = 0.01-0.002). When we combined the number of seizures observed in the latter half of the study (Weeks 4-6), we found a significant reduction in seizures after 20-Gy (P = 0.007), 40-Gy (P = 0.03), 60-Gy (P = 0.03), and 100-Gy (P = 0.03) radiosurgery as compared with control animals. Increasing doses of radiosurgery correlated with higher percentages of rats that became seizure-free by EEG criteria. MRI-determined total sodium concentration in the injected hippocampus was 49.8+/-3 mmol/L, compared with 42.8 mmol/L on the contralateral side (within normal limits). This significant increase in sodium concentration was present in control rats (because of the kainic acid) and did not change with increasing radiosurgery dose. No parenchymal effects from radiosurgery were identified after 20, 40, and 60 Gy, and only two rats had necrosis at 100 Gy. All animals showed hippocampal injury from kainic acid by proton MRI and histological examination.

CONCLUSION

In this rat hippocampal epilepsy model, stereotactic radiosurgery was followed by a significant dose-dependent reduction in the frequency of observed and EEG-defined seizures. These effects were not accompanied by increased radiation-induced structural or metabolic brain injury as assessed by proton and sodium MRI or histological examination. The role of radiosurgery as a new, nondestructive surgical therapy for idiopathic epilepsy warrants further investigation.

Iatrogenic pneumocephalus secondary to intravenous catheterization. Case report

The presence of pneumocephalus in a patient without a history of undergoing intracranial or intrathecal procedures is a significant radiographic finding that portends a violation of the dural barrier or the presence of infection. The authors report a case of iatrogenic pneumocephalus that confounded the evaluation of a patient with unrelated neurological disorders, resulting in unnecessary transfer of the patient and utilization of medical resources. A review of 100 sequential computerized tomography scans obtained in patients for any indication in the emergency department revealed a 6% incidence of iatrogenic intravenous pneumocephalus. Computerized tomography scans revealing pneumocephalus had been obtained for altered mental status, focal motor deficit, seizure, and trauma. More careful intravenous catheterization and recognition of the condition on imaging may avoid similar problems.

Stereotactic radiosurgery for brainstem metastases

OBJECT

Brainstem metastases portend a dismal prognosis. Surgical resection is not part of routine management and radiation therapy has offered little clinical benefit. Radiosurgery provides a safe and effective treatment for many patients with brain metastasis, but its role in the brainstem has not been evaluated. In this study the authors examine the role of radiosurgery in the treatment of brainstem metastases.

METHODS

The authors reviewed the outcomes after stereotactic radiosurgery in 26 patients with 27 brainstem metastases. Tumor locations included the pons (21 tumors) and midbrain (six tumors): 14 patients had additional tumors in other locations. Twenty patients presented with brainstem signs. The median dose to the tumor margin was 16 Gy (range 12-20 Gy). Twenty-four patients received fractionated whole-brain radiation therapy (WBRT) and 12 underwent additional chemotherapy or immunotherapy. The median follow-up time in these patients was 9.5 months (range 1-43 months). After radiosurgery, the local control rate in brainstem tumors was 95%. In one patient in whom the tumor initially decreased in size, tumor enlargement was seen 7 months later. The median survival time was 11 months after diagnosis and 9 months after radiosurgery. Thirteen patients improved, 10 were stable, and three deteriorated. Eventually, 22 patients died, 18 of progression of their extracranial disease, three of new tumor growth (including one hemorrhage into a new brain metastasis), and one of extracranial disease plus new brain tumor growth.

CONCLUSIONS

Although they have slightly lower than the expected survival rates of patients with nonbrainstem tumors, patients with brainstem metastases may achieve effective palliation after stereotactic radiosurgery and WBRT.

Restorative neurosurgery: opportunities for restoration of function in acquired, degenerative, and idiopathic neurological diseases

Historically, neurosurgery has improved the environment of the nervous system to promote maximal spontaneous recovery of function. The population of patients whom we treat at present is a small portion of those who suffer from disabling neurological illnesses. Based on a combination of new technology, and advances in neuroscience, restorative neurosurgery is advancing the frontiers of our specialty, and providing the potential to restore lost function. Significant advancements in gene therapy, the discovery and delivery of neurotrophic factors, and cell transplantation now require neurosurgeons to broaden the scope of our practice so that it includes the restoration of function in an enormous number of patients with acquired, degenerative and idiopathic neurological diseases. In order to meet the present challenge, neurosurgeons must broaden our vision, our role, and our future educational goals. In this review, we summarize the landmark advances in the basic and clinical neurosciences and the results of clinical trials that are driving our evolution from passive reaction to disease to active attempts to restore lost central nervous system function.

Dose reduction improves hearing preservation rates after intracanalicular acoustic tumor radiosurgery

OBJECTIVE

To assess the potential for long-term serviceable hearing preservation in intracanalicular acoustic tumor patients who underwent stereotactic radiosurgery.

METHODS

Between August 1987 and December 1997, 29 patients with intracanalicular acoustic tumors underwent stereotactic radiosurgery at our center using the Leksell gamma knife (Elekta Instruments, Inc., Atlanta, GA). Fifteen assessable patients had serviceable preradiosurgery hearing (pure tone average, < or = 50 dB; speech discrimination score, > or = 50%). We retrospectively analyzed our hearing results and compared hearing preservation in patients who received a minimal tumor dose of 14 Gy or less versus those who received more than 14 Gy to the tumor margin.

RESULTS

No perioperative patient morbidity or mortality was observed. Serviceable hearing was preserved in 11 (73%) of 15 assessable patients (actuarial rate, 65%). Long-term follow-up demonstrated serviceable hearing preservation in 10 (100%) of 10 patients who received marginal tumor doses of 14 Gy or less but in only one of five patients who received more than 14 Gy. Preradiosurgery Gardner-Robertson class was preserved in 49%, and testable hearing was present in 68% of patients who had any testable hearing at presentation. Five patients demonstrated improvement in hearing (three had serviceable and two had nonserviceable hearing before radiosurgery). No patient developed a facial or trigeminal neuropathy. Seven of 13 patients with preoperative tinnitus continued to experience tinnitus in follow-up. Episodic vertigo continued in 3 of the 11 patients who presented with vertigo.

CONCLUSION

Gamma knife radiosurgery (using conformal dose planning, small-beam geometry, and < or = 14 Gy to the margin) prevents tumor growth and achieves excellent hearing preservation rates.

Use of cytological preparations for the intraoperative diagnosis of stereotactically obtained brain biopsies: a 19-year experience and survey of neuropathologists

OBJECT

The goals of this study were to analyze the accuracy of cytological techniques, consisting of touch and smear preparations, for the intraoperative diagnosis of stereotactically obtained brain biopsy samples, and to determine the prevalence of the use of these methods among neuropathologists.

METHODS

A survey regarding preferred methods for intraoperative diagnosis of stereotactically obtained brain biopsy samples was completed by 92 (62%) of 148 neuropathologists. Twenty-three percent of respondents chose frozen-section examination alone; 13% chose one or more cytological methods alone; and the remainder (64%) chose a combination of frozen-section examination and cytology. At the University of Pittsburgh, the neuropathology records for all stereotactic brain biopsies performed from May 1979 through May 1998 were retrospectively reviewed. Of the 946 stereotactic brain biopsies, 316 cases were excluded because the intraoperative neuropathological consultation was not recorded. Thirty-five cases were excluded because frozen-section examinations were performed. Therefore, a total of 595 cases were suitable for analysis. Intraoperative cytological investigation correlated with the final diagnosis in 90% of cases (52% complete correlation and 38% partial correlation). In 11% of cases there was no correlation between the intraoperative and final diagnoses. Intraoperative diagnoses were most accurate in cases of abscess, germinoma, lymphoma, metastasis, and malignant glioma. Overall, 91% of biopsy specimens were diagnostic when examined using the paraffin-embedded section technique. The sensitivity of cytological preparations in detecting a diagnostic specimen was 96% and the specificity in detecting a nondiagnostic specimen was 75%.

CONCLUSIONS

Intraoperative cytological preparations correlated with the final diagnoses in 90% of stereotactic biopsies and had a 96% sensitivity in detecting diagnostic specimens. The highest rate of correlation was noted in cases of abscess, germinoma, lymphoma, metastasis, and malignant glial tumor.

Stereotactic radiosurgery plus whole brain radiotherapy versus radiotherapy alone for patients with multiple brain metastases

PURPOSE

Multiple brain metastases are a common health problem, frequently diagnosed in patients with cancer. The prognosis, even after treatment with whole brain radiation therapy (WBRT), is poor with average expected survivals less than 6 months. Retrospective series of stereotactic radiosurgery have shown local control and survival benefits in case series of patients with solitary brain metastases. We hypothesized that radiosurgery plus WBRT would provide improved local brain tumor control over WBRT alone in patients with two to four brain metastases.

METHODS

Patients with two to four brain metastases (all < or =25 mm diameter and known primary tumor type) were randomized to initial brain tumor management with WBRT alone (30 Gy in 12 fractions) or WBRT plus radiosurgery. Extent of extracranial cancer, tumor diameters on MRI scan, and functional status were recorded before and after initial care.

RESULTS

The study was stopped at an interim evaluation at 60% accrual. Twenty-seven patients were randomized (14 to WBRT alone and 13 to WBRT plus radiosurgery). The groups were well matched to age, sex, tumor type, number of tumors, and extent of extracranial disease. The rate of local failure at 1 year was 100% after WBRT alone but only 8% in patients who had boost radiosurgery. The median time to local failure was 6 months after WBRT alone (95% confidence interval [CI], 3.5-8.5) in comparison to 36 months (95% CI, 15.6-57) after WBRT plus radiosurgery (p = 0.0005). The median time to any brain failure was improved in the radiosurgery group (p = 0.002). Tumor control did not depend on histology (p = 0.85), number of initial brain metastases (p = 0.25), or extent of extracranial disease (p = 0.26). Patients who received WBRT alone lived a median of 7.5 months, while those who received WBRT plus radiosurgery lived 11 months (p = 0.22). Survival did not depend on histology or number of tumors, but was related to extent of extracranial disease (p = 0.02). There was no neurologic or systemic morbidity related to stereotactic radiosurgery.

CONCLUSIONS

Combined WBRT and radiosurgery for patients with two to four brain metastases significantly improves control of brain disease. WBRT alone does not provide lasting and effective care for most patients.

Stereotactic radiosurgery for jugular foramen schwannomas

BACKGROUND

Jugular foramen schwannomas pose difficult management problems because of the surgical risk of lower cranial neuropathy. The indications and results of stereotactic radiosurgery are not well documented.

METHODS

We reviewed our 10-year experience in the management of 17 patients who had jugular foramen schwannomas managed with the gamma knife. Thirteen patients previously had undergone surgery (range, 1-6 resections). Four patients had multiple cranial nerve deficits before microsurgical resection; 12 developed multiple lower cranial nerve palsies after resection. Four patients underwent radiosurgery based on imaging criteria alone. Conformal dose planning (tumor margin dose of 12-18 Gy) successfully encompassed the irregular tumor volumes in all patients.

RESULTS

Follow-up varied from 6 to 74 months. Tumor size decreased in eight patients, remained stable in eight, and increased in one patient during the average follow-up interval of 3.5 years. Six patients improved and 10 others retained their preradiosurgery clinical status. One patient had an increase in tumor size and clinical deterioration 6 months after radiosurgery and underwent microsurgical resection. No patient developed new cranial nerve or other neurological deficits after radiosurgery.

CONCLUSIONS

We believe that gamma knife radiosurgery is an effective alternative to microsurgical resection for patients who have small tumors and intact lower cranial nerve function. It is also effective for patients who have residual or recurrent tumors after microsurgical resection.

Stereotactic radiosurgery for management of deep brain cavernous malformations

The indications for stereotactic radiosurgery for patients with cavernous malformations of the brain are discussed. Specific reference is made to technique and dose selection and to the results and potential complications of this approach. Radiosurgery is an alternative to microsurgical resection for some patients with malformations in high-risk brain locations.

Long-term outcomes after meningioma radiosurgery: physician and patient perspectives

OBJECT

Stereotactic radiosurgery is a primary or adjuvant management approach used to treat patients with intracranial meningiomas. The goal of radiosurgery is long-term prevention of tumor growth, maintenance of the patient's neurological function, and prevention of new neurological deficits. The object of this study is to report longer-term patient outcomes.

METHODS

The authors evaluated 99 consecutive patients who underwent radiosurgery for meningioma between 1987 and 1992. Evaluation was performed using serial imaging tests, clinical evaluations, and a patient survey that was administered between 5 and 10 years after radiosurgery. Four patients underwent two radiosurgery procedures for separate meningiomas. The average tumor margin dose was 16 Gy and the median tumor volume was 4.7 ml (range 0.24-24 ml). Fifty-seven patients (57%) had undergone prior resection, of which 12 procedures were considered "total." Five patients received fractionated radiation therapy before radiosurgery. Eighty-nine patients (89%) had skull base tumors. The clinical tumor control rate (no resection required) was 93%. Sixty-one (63%) of 97 tumors became smaller, 31 (32%) remained unchanged in size, and five (5%) were enlarged. Resection was performed in seven patients (7%), six of whom had undergone prior resection. New neurological deficits developed in five patients (5%) 3 to 31 months after radiosurgery. Twenty-seven (42%) of 65 responding patients were employed at the time of radiosurgery and 20 (74%) of these remained so. Radiosurgery was believed to have been "successful" by 67 of 70 patients who completed an outcomes questionnaire 5 to 10 years later. At least one complication was described by nine patients (14%) and in four patients the complications resolved.

CONCLUSIONS

Five to 10 years after radiosurgery, 96% of surveyed patients believed that radiosurgery provided a satisfactory outcome for their meningioma. Overall, 93% of patients required no other tumor surgery. Incidences of morbidity in this early experience were usually transitory and relatively mild. Radiosurgery provided long-term tumor control associated with high rates of neurological function preservation and patient satisfaction.

Morbidity and survival after 1,3-bis(2-chloroethyl)-1-nitrosourea wafer implantation for recurrent glioblastoma: a retrospective case-matched cohort series

OBJECTIVE

To determine the risks and survival benefit associated with implantation of an absorbable, 1,3-bis(2chloroethyl)-1-nitrosourea-impregnated polymer wafer, we prospectively studied patients with recurrent glioblastoma multiforme and compared them with a demographically matched cohort group.

METHODS

Over a 29-month period, 62 patients underwent operations. All had tumor growth despite standard treatment, a Karnofsky performance score of > or =70, and histopathological confirmation of glioblastoma. Seventeen patients underwent gross total resection with placement of 1,3-bis(2-chloroethyl)-1-nitrosourea wafers (wafer group) at a median 44 weeks from diagnosis (6 women, 11 men; median age, 56 years). A cohort group of 45 patients undergoing surgery for recurrent glioblastoma during the same time period, but not receiving wafers, was identified. Surgery was performed at a median 47 weeks from diagnosis (14 women, 31 men; median age, 54 years).

RESULTS

Within 6 weeks of surgery, 13 complications were identified in 8 patients in the wafer group. In the cohort group, 6 patients sustained 8 complications. We were unable to identify any survival advantage using Kaplan-Meier analysis. In the wafer group, median survival was 58 weeks from diagnosis and 14 weeks from wafer implantation. In the cohort group, median survival was 97 weeks from diagnosis and 50 weeks from operation.

CONCLUSION

1,3-bis(2-chloroethyl)-1-Nitrosourea wafer implantation for recurrent glioblastoma was associated with a higher risk of postoperative complications, particularly those related to infection and wound healing. No clear survival benefit associated with wafer implantation was identified.

Stereotactic radiosurgery for trigeminal schwannomas

OBJECTIVE

Schwannomas that arise from the trigeminal nerve are rare and are usually managed by surgical resection. The role of radiosurgery in the care of patients with these basal tumors remains to be defined.

METHODS

We reviewed the clinical presentation, management, and outcomes for 16 trigeminal schwannoma patients who underwent gamma knife stereotactic radiosurgery. Fifteen of the 16 patients presented with trigeminal sensory dysfunction. Nine patients had tumors in the region of the ganglion, six in the region of the trigeminal nerve root, and one in the region of the mandibular branch. Six patients had undergone one or more previous resections before radiosurgery. Ten underwent radiosurgery as the first procedure. The mean tumor volume was 5.3 cc (range, 1-17.8 cc). The mean tumor margin dose was 15.3 Gy (range, 12-20 Gy).

RESULTS

During the average imaging follow-up of 44 months (range, 8-116 mo), the tumor control rate was 100% (regression in nine patients and no further tumor growth in seven patients). Five patients had improvement of clinical symptoms, and 11 remained unchanged. No new cranial nerve deficit developed in any patient.

CONCLUSION

As a minimally invasive alternative to microsurgery, gamma knife radiosurgery proved to be an alternative primary or adjuvant strategy that controlled tumor growth, did not cause new deficits, and often improved presenting symptoms.

Stereotactic radiosurgery in the management of acoustic neuromas associated with neurofibromatosis Type 2

OBJECT

Stereotactically guided radiosurgery is one of the primary treatment modalities for patients with acoustic neuromas (vestibular schwannomas). The goal of radiosurgery is to arrest tumor growth while preserving neurological function. Patients with acoustic neuromas associated with neurofibromatosis Type 2 (NF2) represent a special challenge because of the risk of complete deafness. To define better the tumor control rate and long-term functional outcome, the authors reviewed their 10-year experience in treating these lesions.

METHODS

Forty patients underwent stereotactic radiosurgery at the University of Pittsburgh, 35 of them for solitary tumors. The other five underwent staged procedures for bilateral lesions (10 tumors, 45 total). Thirteen patients (with 29% of tumors) had undergone a median of two prior resections. The mean tumor volume at radiosurgery was 4.8 ml, and the mean tumor margin dose was 15 Gy (range 12-20 Gy). The overall tumor control rate was 98%. During the median follow-up period of 36 months, 16 tumors (36%) regressed, 28 (62%) remained unchanged, and one (2%) grew. In the 10 patients for whom more than 5 years of clinical and neuroimaging follow-up results were available (median 92 months), five tumors were smaller and five remained unchanged. Surgical resection was performed in three patients (7%) after radiosurgery; only one showed radiographic evidence of progression. Useful hearing (Gardner-Robertson Class I or II) was preserved in six (43%) of 14 patients, and this rate improved to 67% after modifications made in 1992. Normal facial nerve function (House-Brackmann Grade 1) was preserved in 25 (81%) of 31 patients. Normal trigeminal nerve function was preserved in 34 (94%) of 36 patients.

CONCLUSIONS

Stereotactically guided radiosurgery is a safe and effective treatment for patients with acoustic tumors in the setting of NF2. The rate of hearing preservation may be better with radiosurgery than with other available techniques.

The role of stereotactic biopsy in the management of gliomas

Neurosurgeons must use accurate diagnostic techniques that confirm characteristics of individual glial neoplasms before recommending specific treatments. These diagnostic methods must reach all brain locations and be appropriate for patients of all ages and medical conditions. We believe that CT- or MR-based stereotactic biopsy is the best way to guide management in patients who do not require craniotomy for tumor mass effect. As our understanding of the biology of different tumors increases, we anticipate that even more specific therapeutic approaches will be developed that will require a histologic diagnosis and perhaps even new approaches to tumor classification and grading.

Dose selection in stereotactic radiosurgery

Selection of the prescription dose for radiosurgery is the final step in treatment planning. Dose selection should take into account the expectation of treatment success (i.e., tumor control, arteriovenous malformation [AVM] obliteration, and so forth) and complication risks at various doses. Accurately predicting complication risks for individual patients is a complex process that is highly dependent on the radiosurgery treatment volume, the target location, and the nature of the target tissue. Dose-response data for desired outcomes of radiosurgery are sparse and difficult to interpret for most indications, with perhaps the exception of AVM obliteration. This article reviews the principles governing dose-selection and the evolving body of data guiding dose selection in radiosurgery.

A multi-institutional analysis of complication outcomes after arteriovenous malformation radiosurgery

PURPOSE

To better understand radiation complications of arteriovenous malformation (AVM) radiosurgery and factors affecting their resolution.

METHODS AND MATERIALS

AVM patients (102/1255) who developed neurological sequelae after radiosurgery were studied. The median AVM marginal dose (Dmin) was 19 Gy (range: 10-35). The median volume was 5.7 cc (range: 0.26-143). Median follow-up was 34 months (range: 9-140).

RESULTS

Complications consisted of 80/102 patients with evidence of radiation injury to the brain parenchyma (7 also with cranial nerve deficits, 12 also with seizures, 5 with cyst formation), 12/102 patients with isolated cranial neuropathies, and 10/102 patients with only new or worsened seizures. Severity was classified as minimal in 39 patients, mild in 40, disabling in 21, and fatal in 2 patients. Symptoms resolved completely in 42 patients for an actuarial resolution rate of 54% +/- 7% at 3 years post-onset. Multivariate analysis identified significantly greater symptom resolution in patients with no prior history of hemorrhage (p = 0.01, 66% vs. 41%), and in patients with symptoms of minimal severity: headache or seizure as the only sequelae of radiosurgery (p < 0.0001, 88% vs. 34%).

CONCLUSION

Late sequelae of radiosurgery manifest in varied ways. Further long-term studies of these problems are needed that take into account symptom severity and prior hemorrhage history.

Can hearing improve after acoustic tumor radiosurgery?

Advances in noninvasive diagnostic techniques have enabled physicians to diagnose acoustic tumors early, while hearing is still present. Applications of advanced operative techniques have allowed surgeons to decrease progressively the operative mortality to virtually zero, to save facial nerve function in a large number of patients, and even to preserve serviceable hearing in selected patients. Documented improvement in hearing after acoustic tumor surgery is rare. During the last decade, stereotactic radiosurgery has evolved as a noninvasive surgical option for acoustic tumors. Hearing improvement after radiosurgery has not been reported. The authors observed hearing improvement in 21 out of 487 patients who had radiosurgery during a 10-year interval. This article reviews their experience of hearing improvement after radiosurgery and suggests possible reasons that hearing can not only be retained but also improved in selected patients.

The radiobiology of radiosurgery

Radiosurgery is the precise and complete destruction of a chosen target containing healthy or pathological cells, without significant concomitant or late radiation damage to adjacent cells. This article discusses briefly the many uses of radiobiology and considers variables in the treatment, such as dose rate, dose homogeneity, and the issue of possible pharmacological radioprotection for radiosurgery. Comparisons between radiosurgery and fractionation are also made.

Beneficial effects of the radioprotectant 21-aminosteroid U-74389G in a radiosurgery rat malignant glioma model

PURPOSE

To evaluate the radioprotectant effects of the 21-aminosteroid U-74389G on the rat C6 glioma model after stereotactic radiosurgery. Because radiosurgery causes both tumor cytotoxicity, as well as regional brain edema, we hypothesized that this drug might exhibit advantageous or deleterious effects on healthy and neoplastic tissue.

METHODS

Rats were implanted with 10(6) C6 glioma cells into the right frontal brain and randomized to a Control Group (n = 18), radiosurgery on Day 14 (50% isodose = 35 Gy) (n = 15), or radiosurgery preceded by a single 15 mg/kg intravenous dose of 21-aminosteroid (n = 27). All animals were killed by 90 days and evaluated for survival, tumor size, the presence or absence of regional parenchymal edema, or radiation-induced vasculopathy.

RESULTS

After tumor implantation, median survival in the Control Group was 23 days. Significant improvements in median survival were noted after RS alone (median, 31 days; p = 0.02), and RS plus 21-aminosteroid (median, 59 days; p < 0.0001). In the Control Group, mean tumor diameter was 5.4 mm. After RS alone, the mean diameter was 3.2 mm (p = 0.002), and after RS plus 21-aminosteroid, 2.9 mm (p = 0.0002). In the Control Group, the tumor grew as a hypercellular, compact mass. Only 3 of 18 animals had peritumoral edema. In contrast, 7 of 15 animals in the RS group had evidence of edema (p = 0.006), but rats that received 21-aminosteroid showed no increase compared to controls (p = 0.38). Similarly, 6 of 15 animals that had radiosurgery alone showed evidence of vasculopathy (p = 0.005) compared to no animals in the control group and only 2 of 27 aminosteroid-treated animals.

CONCLUSIONS

The 21-aminosteroid U-74389G exhibits a radioprotectant effect on normal brain tissue, but does not appear to protect the tumor in an in vivo rat radiosurgery model. We believe that the observed beneficial effects on healthy brain led to significant prolongation of animal survival; perhaps, by limiting the adverse effects of high-dose radiosurgery. This radioprotectant should now be evaluated in randomized clinical trials in patients with malignant brain tumors.