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PubMed2002

[Ambulatory radiosurgery in cerebral metastatic renal cell carcinoma. 5-year outcome in 58 patients].

Brain metastases (BM) indicate an advanced stage of renal cell cancer (RCC). They pose an increasing challenge to urologists as a result of improved survival due to modern therapy. Median survival of untreated patients with BM who often suffer from neurological deficits is 3 months. Radiosurgery with the Gamma Knife (GK) has increased in use as an alternative to whole brain radiation therapy (WBRT) and/or surgery. This study reports the results of a consecutive series of RCC patients treated for BM by GK radiosurgery during a 5-year period. Between 1994 and 1999, 58 patients with a total of 277 BM and 3.0 (1-19) BM/patient were treated. Because of recurrent BM, 23 (40%) patients received repeated (multiple) GK sessions. The median tumor volume was 3.4 cm3 (0.1-19.1). The median interval between diagnosis of RCC and GK treatment was 2.2 years (0.1-17.2). Symptomatic side effects were detected in 9 (16%) of 58 patients. The median actuarial survival time was 9.9 months. Local tumor control could be achieved in 95% of patients. The GK therapy induced a significant tumor remission accompanied by rapid neurological improvement in 70% of patients. Compared to standard radiotherapy, GK radiosurgery is more effective, less time consuming, and can be repeated. Compared to surgery, radiosurgery is less invasive and better suited to treat multiple metastases in one single session. Surgery and radiosurgery, however, are supplementary methods that are highly effective to control intracerebral metastasizing RCC.

Actuarial Analysis↗
PubMed2000

Stereotactic radiosurgery for hemangioblastomas of the brain.

OBJECTIVE: To assess the effectiveness of stereotactic radiosurgery in achieving tumor control and improving survival in patients with hemangioblastoma, we evaluated results from patients who were managed at the University of Pittsburgh and the Mayo Clinic. PATIENTS AND METHODS: Twenty-seven patients with 29 hemangioblastomas had stereotactic radiosurgery over a 10 year interval. The mean patient age was 32 years (range, 14-75 years). The tumor volumes varied from 0.36 to 27 ml (mean, 3.2 ml), and the mean tumor margin dose was 16 Gy (range, 11.7-20). Clinical and neuroimaging follow-up was obtained for all patients between 0.5 and 9 years (mean, 4 years) after radiosurgery. RESULTS: At this assessment, 21 patients (79%) were alive and six (21%) had died. The median survival after radiosurgery was 6.5 years (actuarial 5 year survival = 75.1 +/- 11.5%). The median survival from the initial diagnosis was 15 years. Twenty two of 29 evaluable tumors were controlled locally. The two-year actuarial control rate was 84.5 +/- 7.1% and at five years, 75.2 +/- 8.9%. Multivariate testing of factors affecting good outcome indicated that smaller tumor volume and higher radiosurgical dose (> 18 Gy) were significant. CONCLUSION: For small to moderate size hemangioblastomas, multiple or recurrent tumors, and for patients who are not surgical candidates, radiosurgery is a safe and effective option to control disease and improve survival.

Adolescent↗
PubMed2005

Linac radiosurgery as a tool in neurosurgery.

Stereotactic radiosurgery is a radiation technique that uses a high radiation dose focused on a stereotactic defined intracranial target in single fraction with high precision. In the 1980s, linear accelerators were introduced as a tool for radiosurgery beneath the already accepted gamma unit. Technique and mechanical precision of LINACs have become equal to the gamma unit and LINAC radiosurgery became more and more used recently. From January 1996 to August 2003 we have treated 237 patients with LINAC radiosurgery. A combination of the University of Florida system and the X Knife System, developed by Radionics, was used in all patients. A number of 110 patients had 161 brain metastases treated, whereas the local tumor control rate was 89.4%. The 1-year survival rate was 54.9% with a median survival of 54 weeks. In 55 patients we have treated 57 meningiomas, mostly located at the skull base (37 out of 55 patients). Local tumor control rate in our patients with skull base meningiomas at 5-year follow up was 97.2%. In this time period, we have also treated acoustic schwannoma, glioma, pituitary adenoma, arteriovenous malformations and patients with trigeminal neuralgia. LINAC radiosurgery has become a daily tool in neurosurgery and changed treatment strategies especially in the treatment of brain metastases and skull base meningiomas towards a less aggressive and multimodality approach. It is not only an alternative to open surgery, but also a very effective adjuvant treatment modality in many neuro-oncological patients, which helps us to enhance tumor control rate, minimize morbidity and increase postoperative quality of life.

Brain Neoplasms↗
PubMed1992

Defining the role of radiosurgery in the management of brain metastases.

The role of stereotactic radiosurgery in the management of recurrent and newly diagnosed brain metastases was evaluated prospectively. From December 1988 to March 1991, 58 lesions in 40 patients were treated with accelerator-based stereotactic radiosurgery. All patients were followed for a minimum of 6 months or to death. The primary purpose was to determine the impact of radiosurgery on local control and its subsequent effects on quality of life. An overall tumor control rate of 82% with a complete response rate of 43% were achieved. As anticipated, the response rate for smaller tumors was substantially better than that for larger tumors (78% for lesions < 2 cm3; 50% for lesions > or = 10 cm3). Although the overall in-field progression rate was 18.5%, only 1/23 (4%) complete responders subsequently recurred. The in-field failure rate is highly comparable with recently published surgical data. Progression outside the brain was noted in two-thirds of patients. One quarter of the deaths were neurologic. The median survival for this minimally selected patient population was 6.5 months. Stereotactic radiosurgery was also associated with improved quality of life as measured by Karnofsky score, neurologic function, and steroid dependence. Long-term steroid dependence was encountered in only four patients. We conclude that stereotactic radiosurgery can be used effectively in patients with brain metastases. In this series, a high tumor response rate was achieved which was associated with improved quality of life.

Adult↗
PubMed1994

Stereotactic radiosurgery for glioblastoma multiforme: report of a prospective study evaluating prognostic factors and analyzing long-term survival advantage.

PURPOSE: Prospective evaluation of the toxicity and efficacy of radiosurgery with external beam radiotherapy in the management of newly diagnosed glioblastoma. METHODS AND MATERIALS: From 5/89 to 12/92, 31 out of 51 patients with glioblastoma multiforme underwent radiosurgery, in addition to 54 Gy in 1.8 Gy/fraction following biopsy (n = 12) or resection (n = 19). Eligibility required supratentorial glioblastoma, tumor not > 4 cm in > 1 axis, age > 18 years, and location > 1 cm from optic chiasm. Patient characteristics were: age 20-78 years (median = 57); 22 male, 9 female; Karnofsky score 20-90 (m = 70), and volume of 2.3-59.7 c.c. (m = 17.4). Eighteen patients were treated with 1 collimator, 5 with 2, 7 with 3, and 1 with 4; peripheral isodoses were 40-90% (m = 72.5) and minimum and maximum tumor dose ranges were 10-20 (m = 12) and 15-35 Gy (m = 18.75). Patients were followed clinically and radiographically every 8-12 weeks to analyze survival, quality of life, and toxicity. RESULTS: With a follow-up of 12-171 weeks, 8 out of 31 (26%) patients are alive. Median survival is 42 weeks. Twelve and 24-month actuarial survival are 38 and 28%. Comparison of the 2-year survival with previous Radiation Therapy Oncology Group patients was carried out using a nonparametric recursive partitioning technique and the observed vs. expected values are 28 vs. 9.7% (p < 0.05). Extent of resection and performance status were associated with improved survival in a multivariate analysis. No significant acute toxicity was encountered. Four patients (13%) developed clinically significant necrosis verified by biopsy or positron emission tomography scan at 9-59 weeks after radiosurgery. CONCLUSION: The improvement in median survival in broadly selected glioblastoma patients treated with radiosurgery is difficult to determine, but the 2-year survival may be superior. Future randomized trials of radiosurgery are recommended, and ad hoc use of this modality should be discouraged.

Adult↗
PubMed1993

Tolerance of cranial nerves of the cavernous sinus to radiosurgery.

PURPOSE: Stereotactic radiosurgery is becoming a more accepted treatment option for benign, deep seated intracranial lesions. However, little is known about the effects of large single fractions of radiation on cranial nerves. This study was undertaken to assess the effect of radiosurgery on the cranial nerves of the cavernous sinus. METHODS AND MATERIALS: We examined the tolerance of cranial nerves (II-VI) following radiosurgery for 62 patients (42/62 with meningiomas) treated for lesions within or near the cavernous sinus. Twenty-nine patients were treated with a modified 6 MV linear accelerator (Joint Center for Radiation Therapy) and 33 were treated with the Gamma Knife (University of Pittsburgh). Three-dimensional treatment plans were retrospectively reviewed and maximum doses were calculated for the cavernous sinus and the optic nerve and chiasm. RESULTS: Median follow-up was 19 months (range 3-49). New cranial neuropathies developed in 12 patients from 3-41 months following radiosurgery. Four of these complications involved injury to the optic system and 8 (3/8 transient) were the result of injury to the sensory or motor nerves of the cavernous sinus. There was no clear relationship between the maximum dose to the cavernous sinus and the development of complications for cranial nerves III-VI over the dose range used (1000-4000 cGy). For the optic apparatus, there was a significantly increased incidence of complications with dose. Four of 17 patients (24%) receiving greater than 800 cGy to any part of the optic apparatus developed visual complications compared with 0/35 who received less than 800 cGy (p = 0.009). CONCLUSION: Radiosurgery using tumor-controlling doses of up to 4000 cGy appears to be a relatively safe technique in treating lesions within or near the sensory and motor nerves (III-VI) of the cavernous sinus. The dose to the optic apparatus should be limited to under 800 cGy.

Abducens Nerve↗
PubMed1996

Radiosurgery for cerebral arteriovenous malformations: assessment of early phase magnetic resonance imaging and significance of gadolinium-DTPA enhancement.

PURPOSE: To evaluate the initial changes within the nidus of arteriovenous malformations (AVMs) and to assess the reaction to the brain tissue surrounding AVMs after radiosurgery by serial magnetic resonance (MR) imaging. METHODS AND MATERIALS: Twenty-one patients, treated using 60Co gamma knife unit with cerebral AVMs, were retrospectively evaluated. Forty-seven follow-up MR images of the 21 patients were performed including 10 patients with two or more serial gadolinium enhanced studies (Gd-MR). Two or more sequential MR angiographies (MRA) were obtained in 13 patients. Three-dimensional (3D) time-of-flight MRA and two-dimensional (2D) phase contrast MRA were used in 13 patients for evaluating the flow changes of AVMs. The follow-up period after radiosurgery ranged from 3 to 30 months (average 10.8 months) and the interval time of MRI ranged from 34 days to 13 months (average 4.9 months). RESULTS: Reduction of nidus size was observed in 14 of 21 patients (67%) between 4 to 13 months on spin echo (SE) images. Complete obliteration was observed on SE images in 4 of these 14 patients; three were confirmed by conventional angiography. New hyperintense areas surrounding the nidus on T2s-weighted images (T2WI) developed in 9 of the 14 patients who showed nidus reduction between 5 to 17 months after radiosurgery; in three patients, size of the hyperintense area started to decrease between 6 to 7 months after its appearance. Probable radiation necrosis of pons developed in one patient 26 months after radiosurgery. The irradiated area within the AVM nidus was significantly enhanced in 8 of the 10 patients who underwent Gd-MR. The degrees of enhancement within the nidus increased with time in 7 of the 10 patients. Overall, total enhancement of irradiated areas was observed in four of the 10 patients; in three of the four, the enhancement decreased in size and degree, indicating nidus reduction. In three patients who had a partial volume irradiation within the nidus, the enhancing areas corresponded with the exact portions of irradiated volume. The nidus reduction was observed in 7 of the 13 patients on MRA during 5 to 13 months after radiosurgery. MRA was more useful compared to SE images in four of the seven patients in evaluating the size change of AVM nidus, feeding arteries, and draining veins. CONCLUSION: Magnetic resonance imaging and MRA were useful in assessing the progress of nidus reduction. T2-weighted imaging was sensitive to radiation-induced reaction in and around the AVM nidus. The enhancement within the AVM nidus on Gd-MR may represent the initial sign of nidus reduction and demonstrates the exact location of irradiation in the nidus. The changes of the enhancement pattern are presumed to represent the processes of nidus reduction and irradiated reaction within the AVM nidus.

Adolescent↗
PubMed2004

Radiation-induced changes of brain tissue after radiosurgery in patients with arteriovenous malformations: correlation with dose distribution parameters.

PURPOSE: To investigate the correlation of radiation-induced changes of brain tissue after radiosurgery in patients with cerebral arteriovenous malformations (AVMs) with treatment planning and dose distribution parameters. METHODS AND MATERIALS: The data from 73 AVM patients with complete follow-up information who underwent stereotactic linear accelerator radiosurgery at our institution between 1993 and 1998 were analyzed. Patients were treated with 11-14 noncoplanar fields shaped by a micromultileaf collimator. A median dose of 19 Gy (range, 13.3-22 Gy) was prescribed to the 80% isodose, which completely encompassed the target. Patients were followed at 3-month intervals the first year and then every 6 months with MRI and neurologic examinations. No patient developed radiation necrosis. The end point of radiation-induced tissue changes on follow-up neuroimaging (i.e., edema, blood-brain barrier breakdown [BBBB], and edema and/or BBBB combined) was evaluated. Each end point was further differentiated into four levels with respect to the extent of the image change (i.e., small, intermediate, large, and very large). The correlation of each end point was investigated for several treatment planning parameters, including prescribed dose and the absolute size of the AVM target volume. In addition, a number of dose-volume variables were calculated from each patient's dose distribution in the brain, including the mean dose to a specified volume of 16 and 20 cm(3) that was given the highest dose (Dmean16 and Dmean20, respectively), and the absolute and percentage of brain volume (including the AVM target) receiving a dose of at least 8, 10, and 12 Gy (V8-V12, and V8(rel)-V12(rel), respectively). These parameters were also determined excluding the AVM target volume from the considered volume (subscript "excl"). The correlation of all treatment planning and dose-volume parameters with outcome was assessed in univariate Cox proportional hazards models. The results were assessed by p values (statistical significance for p < or =0.05), residual deviance (ResDev) of the fits, and odds ratios. RESULTS: The prescribed dose was not predictive of outcome (p >0.05 for all end points). The AVM target volume correlated significantly with large edema, as well as large edema and/or BBBB. V12 and Dmean20 were significantly associated with all end points, except very large edema and large BBBB. Patients with V12 of 27.6 cm(3) (Dmean20 of 18.9 Gy) had a 2.8-fold (fourfold) higher risk of developing edema and/or BBBB with large extent than those with V12 of 4.2 cm(3) (Dmean20 of 8.4 Gy). For all end points, V12(rel) correlated worse with outcome compared with V12 (e.g., end point of large edema and/or BBBB: ResDev = 85.8 and 86.5 for V12 and V12(rel), respectively). Excluding the AVM target volume from the considered irradiated volume led to only small changes in the resulting correlations (e.g., end point of small edema and/or BBBB: ResDev = 99.0 and 98.7 for V12 and V12(excl), respectively, and ResDev = 96.1 and 96.1 for Dmean20 and Dmean20(excl), respectively). Throughout the analysis, V8-V12, Dmean20, and Dmean16 yielded similar results and none of these parameters could be favored over the others. CONCLUSION: Radiation-induced changes of brain tissue after AVM radiosurgery can be well predicted by single dose distribution parameters that are a function of both dose and volume. These can be used to quantify dose-volume response relations. Studies of this nature will eventually help to improve our current understanding of the mechanisms leading to radiation-induced tissue changes after AVM radiosurgery and to optimize radiosurgery treatment planning.

Adolescent↗
PubMed2004

Gamma knife radiosurgery for GH-secreting microadenoma with empty sella.

We report a case of a growth hormone secreting microadenoma associated with empty sella treated by gamma knife radiosurgery and we evaluate the effectiveness of radiosurgery for this lesion. A 58-year-old female complained of an acromegalic appearance for 10 years. Magnetic resonance imaging revealed an enlarged sella floor with a compressed, but slightly enlarged pituitary gland. Serum GH values were 8.52 ng/ml. From these results, we diagnosed the presence of a GH-secreting pituitary microadenoma with empty sella. Stereotactic gamma knife radiosurgery was performed to treat the adenoma. The treatment dose was 30 Gy for the tumour margin (50% isodose). The patient was monitored for 5 years without any reported problem. Serum GH values were gradually decreased to 4.1 and 3.5 ng/ml at 1.6 and 3 years. Serum GH values at 5 years after radiosurgery were 1.8 ng/ml within 2 h after glucose load and serum IGF-1 was normalized. We conclude that gamma knife radiosurgery can be an useful alternative treatment modality for GH-secreting adenoma with empty sella in the selected patients when surgery is contraindicated as the primary treatment.

Adenoma↗
PubMed2000

Radiosurgery for bilateral neurinomas associated with neurofibromatosis type 2.

OBJECTIVE: The clinical course of bilateral acoustic tumors associated with neurofibromatosis (NF2) is generally troublesome, and no definite treatment strategy has been established. Follow-up results of bilateral acoustic tumors after radiosurgery are reported herein. METHODS: The current indications for radiosurgery are 1) a growing tumor less than 30 mm in mean diameter, 2) the ipsilateral ear has no serviceable hearing, and 3) there is risk of brain stem compression or brain stem dysfunction. Twenty cases of bilateral acoustic tumors were treated with the gamma knife, including 7 males and 13 females. The mean age was 38.2 years and the mean tumor size 24.4 mm. The tumors were treated with mean maximum and marginal doses of 26.8 Gy and 13.0 Gy, respectively. Among them, 12 patients had profound hearing loss in the ipsilateral (treated) ear, but the other 8 had serviceable hearing. RESULTS: Tumors treated with radiosurgery showed central necrosis in 60% of the cases at 6 months and in 70% at 9 months after radiosurgery. Thereafter, the tumors often demonstrated slow regression. The rate of tumor shrinkage was 20% at 12 months, 35% at 24 months, and almost 60% at 36 months. At the last follow-up (mean 33.6 months), the tumors demonstrated shrinkage in 50% and tumor control in 100%. The contralateral tumors were stable in 12 (60%) and enlarged in 8 (40%). Preservation of serviceable hearing ipsilaterally was obtained in 33.3%. Deterioration of ipsilateral facial nerve function, either in the natural course or as a complication, occurred in 10%. CONCLUSIONS: Because of good tumor control and tumor shrinkage as well as an acceptable complication rate, radiosurgery should be incorporated in the treatment strategy for bilateral acoustic tumors associated with NF2.

Adolescent↗
PubMed1998

The effect of incomplete patient follow-up on the reported results of AVM radiosurgery.

BACKGROUND: The reported efficacy of AVM radiosurgery--80-85% 2-year obliteration rate--is based exclusively on the results of follow-up arteriography in a small percentage of treated patients; it is therefore inaccurate. We examined the effect of incomplete follow-up on the results of AVM radiosurgery. METHODS: We reviewed the results of AVM radiosurgery in 82 patients after a minimum of 24 months of follow-up. Patients were not preselected to undergo arteriography on the basis of any other imaging study. Data were analyzed using the Kaplan-Meier method and stratified by size of AVM. Results were compared with those obtained from the same data using the reporting techniques described in the literature. RESULTS: When data analysis was limited to patients who had follow-up arteriography, the 2-, 3-, and 4-year obliteration rates were 37%, 73%, and 84% after a minimum 24-month follow-up. Using Kaplan-Meier analysis the 2-, 3-, and 4-year obliteration rates were 32%, 55%, and 55% (95% CI = +/-18%), respectively. The 2-year obliteration rate was 43% for AVMs <30 mm in diameter and 16% for AVMs >30 mm in diameter, respectively. CONCLUSION: If data analysis is limited to the patients who undergo follow-up arteriography, the obliteration rate of AVM radiosurgery is overestimated. The actual 2-year obliteration rate if all data is considered is in the range of 40% rather than the commonly reported 80%. Therefore, treated patients are exposed to the risk of intracerebral hemorrhage for a longer period than previously appreciated. Compulsive long-term follow-up is required to document the true AVM obliteration rate after treatment by radiosurgery.

Algorithms↗
PubMed1999

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.

Adult↗
PubMed2004

Whole brain radiation therapy with or without stereotactic radiosurgery boost for patients with one to three brain metastases: phase III results of the RTOG 9508 randomised trial.

BACKGROUND: Brain metastases occur in up to 40% of all patients with systemic cancer. We aimed to assess whether stereotactic radiosurgery provided any therapeutic benefit in a randomised multi-institutional trial directed by the Radiation Therapy Oncology Group (RTOG). METHODS: Patients with one to three newly diagnosed brain metastases were randomly allocated either whole brain radiation therapy (WBRT) or WBRT followed by stereotactic radiosurgery boost. Patients were stratified by number of metastases and status of extracranial disease. Primary outcome was survival; secondary outcomes were tumour response and local rates, overall intracranial recurrence rates, cause of death, and performance measurements. FINDINGS: From January, 1996, to June, 2001, we enrolled 333 patients from 55 participating RTOG institutions--167 were assigned WBRT and stereotactic radiosurgery and 164 were allocated WBRT alone. Univariate analysis showed that there was a survival advantage in the WBRT and stereotactic radiosurgery group for patients with a single brain metastasis (median survival time 6.5 vs 4.9 months, p=0.0393). Patients in the stereotactic surgery group were more likely to have a stable or improved Karnofsky Performance Status (KPS) score at 6 months' follow-up than were patients allocated WBRT alone (43% vs 27%, respectively; p=0.03). By multivariate analysis, survival improved in patients with an RPA class 1 (p<0.0001) or a favourable histological status (p=0.0121). INTERPRETATION: WBRT and stereotactic boost treatment improved functional autonomy (KPS) for all patients and survival for patients with a single unresectable brain metastasis. WBRT and stereotactic radiosurgery should, therefore, be standard treatment for patients with a single unresectable brain metastasis and considered for patients with two or three brain metastases.

Adult↗
PubMed2000

Calculation of cranial nerve complication probability for acoustic neuroma radiosurgery.

PURPOSE: Estimations of complications from stereotactic radiosurgery usually rely simply on dose-volume or dose-diameter isoeffect curves. Due to the sparse clinical data available, these curves have typically not considered the target location in the brain, target histology, or treatment plan conformality as parameters in the calculation. In this study, a predictive model was generated to estimate the probability of cranial neuropathies as a result of acoustic schwannoma radiosurgery. METHODS AND MATERIALS: The dose-volume histogram reduction scheme was used to calculate the normal tissue complication probability (NTCP) from brainstem dose-volume histograms. The model's fitting parameters were optimized to provide the best fit to the observed complication data for acoustic neuroma patients treated with stereotactic radiosurgery at the University of Florida. The calculation was then applied to the remainder of the patients in the database. RESULTS: The best fit to our clinical data was obtained using n = 0.04, m = 0.15, and alpha/beta = 2.1 Gy(-1). Although the fitting parameter m is relatively consistent with ranges found in the literature, both the volume parameter, n, and alpha/beta are much smaller than the values quoted in the literature. The fit to our clinical data indicates that brainstem, or possibly a specific portion of the brainstem, is more radiosensitive than the parameters in the literature indicate, and that there is very little volume effect; in other words, irradiation of a small fraction of the brainstem yields NTCPs that are nearly as high as those calculated for entire volume irradiation. These new fitting parameters are specific to acoustic neuroma radiosurgery, and the small volume effect that we observe may be an artifact of the fixed relationship of acoustic tumors to specific regions of the brainstem. Applying the model to our patient database, we calculate an average NTCP of 7.2% for patients who had no cranial nerve complications, and the average NTCP for was 66% for patients who sustained a cranial neuropathy. For the entire patient population, the actual percentage of patients suffering either facial or trigeminal neuropathy was 14.7%, whereas the calculated average NTCP was 14.8%. DISCUSSION: NTCP calculations using brainstem dose-volume histograms can be used to estimate the rate of cranial neuropathies from acoustic neuroma radiosurgery. More clinical data and further study will lead to refinement of the model with time.

Brain Stem↗
PubMed2001

Stereotactic radiosurgery in the management of angiographically occult vascular malformations.

PURPOSE: To evaluate the role of stereotactic radiosurgery in the treatment of angiographically occult vascular malformations (AOVMs). METHODS AND MATERIALS: From 1987 to 1996, 21 patients, 10 males and 11 females, median age of 41 years (range: 7-75 years), with an intracerebral AOVM underwent stereotactic radiosurgery at our institution. All were considered at high risk for surgical intervention. The vascular lesions were located in the brainstem (17 patients), basal ganglia (2), occipital lobe (1), and cerebellum (1). Diagnosis was based on high-resolution magnetic resonance imaging (MRI). Clinical presentation at onset included previous intracerebral hemorrhage (20 patients) and epilepsy (1). All patients were treated with a linac-based radiosurgical technique. The median dose delivered was 25 Gy (range 13-50 Gy), typically prescribed to the 80-90% isodose surface (range 50-90%), which corresponded to the periphery of the vascular malformation. Patients were followed by clinical neurologic assessment and by MRI on a regular interval basis. RESULTS: Follow-up was obtained in 20 patients; clinical or MRI information was not available for 1 patient, and this patient was excluded from our analysis. At a median follow-up of 77 months (range: 4-141 months), follow-up MRIs postradiosurgery do not demonstrate any changes in the appearance of the AOVM. Four patients developed an intracranial bleed at 4, 8, 35, and 57 months postradiosurgery. Annual hemorrhage rates were considerably higher in the observation period preradiosurgery than postradiosurgery (30% vs. 3.2%, p < 0.001). Complications postradiosurgery were observed in 4 patients. Three patients developed mild to moderate edema surrounding the radiosurgical target, expressed at 5, 8, and 24 months, respectively. In all cases, the edema was transient and resolved completely on subsequent MRIs. One of the 4 patients developed radiation necrosis 8 months after radiosurgery. CONCLUSION: The use of stereotactic radiosurgery in the treatment of AOVM continues to be controversial. Our results appear to show a reduction in the risk of symptomatic hemorrhage post treatment. Patients with previous history of hemorrhage or progressive neurologic deficit and small, well circumscribed lesions may benefit from a trial of stereotactic radiosurgery.

Adolescent↗
PubMed2002

Conformal radiotherapy optimization with micromultileaf collimators: comparison with radiosurgery techniques.

PURPOSE: Conformal radiotherapy (CRT) consists of irradiating the target volume while avoiding the healthy peripheral tissues and organs at risk as far as possible. One technique used to treat intracranial tumors consists of using micromultileaf collimators (MMLCs). Given the dose constraints involved, it is of interest to optimize MMLC irradiation parameters and compare the results of this technique with those of conventional radiosurgery (RT) techniques (Gamma Knife and linear accelerator stereotactic RT). METHODS AND MATERIALS: MMLC protocols are optimized in two stages. The orientation of the fields, delimited by a beam's eye view technique, is determined using a genetic algorithm method. The weighting of the fields and subfields when using intensity modulation and the position of the leaves are optimized using a simulated annealing method. We compared the results obtained for 8 clinical cases using 5 intensity-modulated fields with those obtained using the two radiosurgery techniques. The comparison indexes are those defined by the Radiation Therapy Oncology Group (RTOG). RESULTS: The results of this study demonstrated the advantages of using intensity modulation and the improvement obtained for the RTOG indexes in the case of CRT with MMLC, although the healthy peripheral tissues were less exposed to radiation with the radiosurgery techniques. The results also highlight the difficulty encountered with radiosurgery techniques in obtaining satisfactory dose homogeneity when the protocol is defined with numerous iosocenters. CONCLUSION: In CRT with MMLC, intensity modulation makes it possible to reduce the number of fields used. It is especially useful to optimize the orientations in the case of target volumes of complex shape or when volumes at risk are in the vicinity of the target. If used correctly, MMLC can be a valuable alternative to conventional radiosurgery techniques.

Algorithms↗
PubMed2003

A simple and reliable index for scoring rival stereotactic radiosurgery plans.

PURPOSE: A simple and robust index for ranking rival stereotactic radiosurgery plans is presented. METHODS: The radiosurgery plan score index, CGI (Conformity/Gradient Index), is an average of a conformity score and a gradient score. Computation of the CGI score is simple, requiring only three pieces of data: (1) the total volume irradiated to the prescription isodose level, (2) the volume of the target, and (3) the total volume irradiated at half of the prescription isodose level. The overall CGI Index is a simple function of these three pieces of data. RESULTS: When multiple sets of rival stereotactic radiosurgery plans were ranked with respect to this single score index, the resulting plan rankings closely matched the plan rankings according to biologic indices (calculated nontarget brain normal tissue complication probabilities). CONCLUSIONS: The CGI is a simple and fast plan evaluation tool that can assist the radiosurgery planner in evaluating and optimizing multiple candidate radiosurgery plans.

Adult↗
PubMed1998

Fractionated stereotactic radiosurgery and concurrent taxol in recurrent glioblastoma multiforme: a preliminary report.

PURPOSE: Surgery and systemic chemotherapy offer modest benefit to patients with recurrent glioblastoma multiforme. These tumors are associated with rapid growth and progressive neurological deterioration. Radiosurgery offers a rational alternative treatment, delivering intensive local therapy. A pilot protocol to treat recurrent glioblastoma was developed using fractionated stereotactic radiosurgery with concurrent intravenous (i.v.) Taxol as a radiation sensitizer. METHODS AND MATERIALS: The treatment outcome was analyzed in 14 patients with recurrent glioblastoma treated with fractionated stereotactic radiosurgery and concurrent Taxol. Median tumor volume was 15.7 cc and patients received a mean radiation dose of 6.2 Gy at 90% isodose line, 4 times weekly. The median dose of Taxol was 120 mg/m2. RESULTS: The median survival was 14.2 months, 1-year survival was 50%. CONCLUSIONS: Survival for this small group of patients was similar to or better than historical controls or patients treated with single-fraction radiosurgery alone. This data should stimulate the investigation of both fractionated radiosurgery and the development of radiation sensitizers to further enhance treatment.

Adult↗