Results Of Gamma Knife Surgery Research Articles

Gamma Knife Thalamotomy for a Medically Refractory Tremors: Longitudinal Evaluation of Clinical Effects and MRI Response Patterns.

The present longitudinal study evaluated the results of Gamma Knife surgery (GKS) for medically refractory tremors. The outcome after Gamma Knife thalamotomy targeting the ventral intermediate nucleus (VIM) was analyzed in 17 patients (9 men and 8 women; mean age 72years) with either Parkinson's disease or an essential tremor, who were followed up for at least 2years after treatment. Clinical and magnetic resonance imaging (MRI) examinations were done before and every 3months after GKS. The mean rates of symptom improvement (a decrease in the tremor frequency) were 6%, 39%, 63%, and 64% at 3, 6, 12, and 24monthsafter treatment, respectively. The defined MRI response patterns included a minimum reaction (in 3 patients), a normal reaction (in 11 patients), and a hyperreaction (in 3 patients). They were not associated with any evaluated pretreatment, radiosurgical, or outcome parameter, although 2 patients with a hyperreaction exhibited mild-to-moderate motor weakness in the contralateral limbs. Linear contrasting of the border between the thalamus and the internal capsule adjacent to the lesion site was noted on follow-up MRI in 13 cases and was associated with a higher symptom improvement rate. GKS allows effective and safe management of medically refractory tremors. The treatment is characterized by variable MRI response patterns. Some imaging findings during follow-up may be associated with clinical effects.

Gamma knife radiosurgery on the trigeminal ganglion for idiopathic trigeminal neuralgia: Results and review of the literature.

Background:In the present study, we evaluate the results of gamma knife surgery (GKS) for the treatment of trigeminal neuralgia (TN) using the trigeminal ganglion (TG’) and the adjacent fibers of trigeminal nerve as a target.Methods:From February 2013 to July 2017, we treated 30 cases of TN with GKS. In this group, all patients had an idiopathic typical TN. The radiosurgical target was conformed through two isocenters, 8 and 4 mm at the cavum de Meckel. The maximum dose was 86 Gy using the isodose line of 50%. The median age of the patients was 58.5 (range 28–94) years old, and the median time from diagnosis to GKS was 94 months (range 13–480 months). The median follow-up was 28.5 (range 12–49) months. Clinical outcomes were analyzed. Univariate and multivariate analyses were performed to evaluate factors that correlated with a favorable, pain-free outcome.Results:The mean time to relief of pain was 7 (range 1–40) days. The percentage of patients with significant pain relief was 93.3%. Relapse in pain was noted in four patients at 3, 16, 19, and 36 months. Nine patients were treated in acute status. Fourteen patients had intense pain between 1 and 7 days before the procedure. Among those with the recurrence of their symptoms, one patient had a microvascular decompression. Multivariate regression adjusted for age and sex suggests that, by 40 months, 70% of the patients treated with radiosurgery will remain pain free. At the last follow-up, GKS resulted in pain relief in 86.6% of patients. Our analysis suggests that, using this technique, we can expect that approximately 70% of patients with TN will have some degree of pain improvement at 3 years’ post radiosurgery.Conclusions:GKS on TG appears to be a reasonable treatment option with short latency period, minor collateral effects, and high percentage of pain control. The mechanism of action of radiosurgery could be related to the inactivation of the satellite glial cells in the TG.

P17.04 Gamma knife surgery for Cavernous sinus cavernous hemangioma - comparative results to surgery and radiation therapy

Objectives: Cavernous hemangiomas occur very rarely in the cavernous sinus. These lesions share the same histologic features as intracerebral lesions, but their clinical picture is quite different. The objectives of this study are to evaluate the efficacy of Gamma Knife Surgery (GKS) on cavernous sinus cavernous hemangiomas (CSCHs) and to compare the results of GKS to those of surgical treatment and fractionated radiation therapy (FRT). Methods: Before 2000, we operated 7 cases of CSCHs. We have performed GKS for 26 cases and FRT for 4 cases since 2000. Among 26 cases that were treated by GKS, two patients were performed other treatment before GKS (surgery and FRT). Thirteen patients were diagnosed incidentally during the work up of other reason such as headache or head trauma. Most common symptom was cranial nerve palsy (ptosis, diplopia and facial sense change) in 12 cases. Results: Of 7 surgically treated cases, 4 patients had already had extraocular muscle palsy preoperatively. Gross total resection (GTR) was achieved using extradural approach in all 7 cases and there has been no tumor recurrence during follow up. However, 2 new trigeminal nerve deficits developed after operation. FRT was performed for 4 cases, usually large ones. All 4 tumors were well controlled, however, symptomatic radiation necrosis was developed at brainstem in 1 case. Twenty-six patients were treated by GKS. The mean tumor volume was 9.7 cm3 (range 0.5-31.6). The prescription dose to the tumor margin varied from 13 to 15 Gy by the proximity to the optic pathway. The mean follow up period was 46.1 months (range 11.1-131.1). Eleven patients showed marked clinical improvement within 3 months. All the cases showed significant shrinkage of the tumors was noted within 6 months and 11 patients had complete remission at the last follow up (34%). Mean residual volume comparing to pre-GKS initial volume was 20.8% (range 0-70%). There was no complication related to GKS during their follow up. Conclusion: Even though surgical resection for CSCHs is curative treatment, it is not always easy and safe. Because of the radiosensitive nature of CSCHs, FRT could be another treatment option in case of large CSCHs, but it has potential radiation-related risk. GKS is an effective and safe treatment modality and could be a treatment of choice for CSCHs.

Gamma Knife Surgery for Metastatic Brain Tumors from Gynecologic Cancer

The incidences of metastatic brain tumors from gynecologic cancer have increased. The results of Gamma Knife surgery (GKS) for the treatment of patients with brain metastases from gynecologic cancer (ovarian, endometrial, and uterine cervical cancers) were retrospectively analyzed to identify the efficacy and prognostic factors for local tumor control and survival. The medical records were retrospectively reviewed of 70 patients with 306 tumors who underwent GKS for brain metastases from gynecologic cancer between January 1995 and December 2013 in our institution. The primary cancers were ovarian in 33 patients with 147 tumors and uterine in 37 patients with 159 tumors. Median tumor volume was 0.3 cm(3). Median marginal prescription dose was 20 Gy. The local tumor control rates were 96.4% at 6 months and 89.9% at 1 year. There was no statistically significant difference between ovarian and uterine cancers. Higher prescription dose and smaller tumor volume were significantly correlated with local tumor control. Median overall survival time was 8 months. Primary ovarian cancer, controlled extracranial metastases, and solitary brain metastasis were significantly correlated with satisfactory overall survival. Median activities of daily living (ADL) preservation survival time was 8 months. Primary ovarian cancer, controlled extracranial metastases, and higher Karnofsky Performance Status score were significantly correlated with better ADL preservation. GKS is effective for control of tumor progression in patients with brain metastases from gynecologic cancer, and may provide neurologic benefits and preservation of the quality of life.

Gamma Knife Surgery for Brain Metastasis from Hepatocellular Carcinoma

ObjectivesThe authors evaluated the results of Gamma knife surgery (GKS) for the treatment of metastatic brain tumors from hepatocellular carcinoma (HCC).Methods and ResultsThe authors conducted a retrospective review of the clinical characteristics and treatment outcomes in 14 patients with metastatic brain tumors from HCC who underwent GKS. Twelve (85.7%) patients were male. The mean age of the patients was 53±12 years. There were totally 22 brain metastases in 14 patients and 8 patients (57.1%) presented with a single brain lesion. Intracranial hemorrhages occurred in 13 (59.1%) of the 22 lesions. The mean KPS score was 81±14 (range 50–100). Eleven (78.6%) patients were classified as RTOG RPA Class 2. The mean tumor volume was 8.16±8.15 cm3 (range 0.59–27.0 cm3). The mean marginal dose prescribed was 18.7±3.2 Gy (range 10.0–22.0 Gy). The mean number of shots administered was 10±9 (range 1–27). The median overall survival time after GKS was 5.0±0.93 months (95% CI 3.2–6.8). No complications related to the radiosurgical treatment were identified. Multivariate analysis showed that the total volume of brain metastases, the RTOG RPA class and serum AFP level were significantly correlated with patients’ survival time.ConclusionsAlthough survival was extremely poor in patients with brain metastasis (BM) from HCC, GKS was shown to lead to prolongation of the survival time. Accordingly, GKS can be considered as a valuable treatment option for proper patients with HCC BM.

Results of Gamma Knife surgery for Cushing's disease

Cushing's disease is a challenging neuroendocrine disorder. Although resection remains the primary treatment option for most patients, the disease persists if there is residual or recurrent tumor. Stereotactic radiosurgery has been used to treat patients with persistent Cushing's disease after a prior resection. The authors report on the long-term risks and benefits of radiosurgery for Cushing's disease. A retrospective review of a prospectively collected database of radiosurgery patients was undertaken at the University of Virginia. All patients with Cushing's disease treated with Gamma Knife surgery (GKS) were identified. Those without at least 12 months of clinical and radiological follow-up were excluded from this analysis. Rates of endocrine remission, tumor control, and adverse events were assessed. Statistical methods were used to identify favorable and unfavorable prognostic factors. Ninety-six patients with the required follow-up data were identified. The mean tumor margin dose was 22 Gy. The median follow-up was 48 months (range 12-209.8 months). At the last follow-up, remission of Cushing's disease occurred in 70% of patients. The median time to remission among all patients was 16.6 months (range 1-165.7 months). The median time to remission in those who had temporarily stopped taking ketoconazole at the time of GKS was 12.6 months, whereas it was 21.8 months in those who continued to receive ketoconazole (p < 0.012). Tumor control was achieved in 98% of patients. New loss of pituitary function occurred in 36% of patients. New or worsening cranial neuropathies developed in 5 patients after GKS, with the most common involving cranial nerves II and III. Gamma Knife surgery offers a high rate of tumor control and a reasonable rate of endocrine remission in patients with Cushing's disease. The cessation of cortisol-lowering medications around the time of GKS appears to result in a more rapid rate of remission. Delayed hypopituitarism and endocrine recurrence develop in a minority of patients and underscore the need for long-term multidisciplinary follow-up.

Clinical results of Gamma Knife surgery for cavernous sinus hemangiomas

The purpose of this study was to gain an understanding of the efficacy and safety of Gamma Knife surgery (GKS) for the treatment of cavernous sinus hemangiomas (CSHs). The authors report on 16 patients who underwent GKS as a primary or adjuvant treatment for CSH. Sixteen patients harboring CSHs (14 women and 2 men ranging in age from 21 to 65 years [mean 41.3 years]) underwent GKS at West China Hospital. In 4 patients the diagnosis was based on histological findings; in the other 12 patients it was based on findings on MR images. After patients were given a local anesthetic agent, the treatments were performed using a Leksell Gamma Knife model C. Gadolinium-enhanced MR images of T1-weighted, T2-weighted, and FLAIR sequences were obtained to determine the pretreatment location of the lesion. A mean peripheral dose of 13.3 Gy (range 11-14 Gy) was directed to the 40%-50% isodose line. The mean follow-up time in this study was 21.5 months (range 12-36 months). In 11 of 12 patients with symptoms, clinical improvement was reported at an average of 3.3 months (range 1-8 months) after GKS. Significant or partial tumor shrinkage was observed in 14 patients (87.5%) at the last follow-up. No new neurological impairments were reported after GKS. Magnetic resonance imaging may play an important role in the preoperative diagnosis of CSHs. Gamma Knife surgery may be a safe and effective primary or adjuvant treatment option for CSHs; however, long-term follow-up with more cases is needed to verify the benefits of this treatment.

Long-term results of Gamma Knife surgery for uveal melanomas

Object Gamma Knife surgery (GKS) is currently believed to be a safe and minimally invasive modality in the treatment of uveal melanomas. It could be used as an alternative treatment to enucleation, preserving the eyeball as well as visual function. The authors report their experiences with GKS for uveal melanomas for the period from February 1998 to December 2006. Methods Twenty-two patients with uveal melanoma were enrolled in this study. The population consisted of 12 men and 10 women with a mean age of 53.4 years (range 24–79 years). The mean tumor volume was 877 mm3, and the mean margin dose was 45.6 Gy. The median follow-up period was 67 months (range 3–126 months). All of the patients had received a diagnosis and referral from an ophthalmology clinic; the patients underwent a preoperative orbital examination that included MRI. Results Tumor regression was achieved in 20 patients (90.9%), whereas tumor progression was observed in 2 patients (9.1%) 3 years after GKS. The cumulative 1-year and 2-year mean rates of tumor thickness reduction were 18.8% and 42.8%, respectively. The mean rate of tumor volume reduction was 63.7%. The rate of eye retention 5 years after radiosurgery was 77.3% (17 of 22 patients). Overall visual acuity was reduced after GKS in all patients; 14 patients (63.6%) displayed preserved visual function better than hand-movement perception. The most frequent side effect was cataract, which was detected in 9 patients (40.9%); this was followed in frequency by radiation-induced retinopathy in 5 patients (22.7%). Conclusions Gamma Knife surgery provides excellent local control of uveal melanomas with a decrease in volume over time. This procedure not only preserves the eyeball and its potential visual function, but also decreases the potential for hematological dissemination and achieves sufficient local tumor control with a gradual reduction in volume.

Long-term Results of Gamma Knife Surgery for Partially Embolized Arteriovenous Malformations

The effectiveness and risk of gamma knife surgery (GKS) in the management of partially embolized cerebral arteriovenous malformations (AVMs) remain to be elucidated. To evaluate the long-term imaging and clinical outcomes of GKS in AVM patients who had undergone previous partial embolization and compare the results with patients treated with GKS alone. A total of 215 embolized AVMs were analyzed. The mean patient age was 32.9 years. The mean volume of the nidus was 4.6 mL (range, 0.1-29.4 mL), and the mean prescription dose was 19.6 Gy (range, 4-28 Gy). This group was compared with 729 nonembolized AVMs. After embolization and GKS, angiographically confirmed total obliteration of the AVMs was significantly lower (33%) compared with patients in whom GKS was used alone (60.9%; P < .001). However, the mean nidus size was larger and the Spetzler-Martin grade was higher for the embolized AVMs compared with the nonembolized AVMs. Radiation-induced changes occurred more often in the embolized (43.4%) than the nonembolized (33.4%) AVMs (P = .028). Permanent neurological deficits associated with radiation-induced changes occurred in 2.7% of the embolized compared with 1.3% of the nonembolized patients (P = .14). In our retrospective and historical series, the long-term results suggest that the obliteration rate is significantly lower in embolized AVMs compared with nonembolized AVMs, also because of the fact that the combined treatment is applied to higher grade AVMs; the percentage of grade III-V AVMs was 58.6% and 48.8% for nonembolized AVMs.

Editorial: Radiosurgery and deep arteriovenous malformations

Cheng et al.1 present the results of Gamma Knife surgery, collected over 3 decades, in 182 patients with basal ganglia (85) and thalamic (97) arteriovenous malformations (AVMs) followed up for more than 2 years. The mean nidus volume was 3.4 cm3 (range <1 to 29 cm3), and the mean margin dose was 21 Gy (range 10–28 Gy). Half of the AVMs were angiographically obliterated after a single GKS treatment, and roughly one-third of those retreated were angiographically obliterated, giving an overall definitive cure rate of 58%. If one includes MR imaging–suspected obliterations, the rate is about 66%, and if one includes lesions with only a residual venous shunt, the rate is close to 75%, but the authors rightly caution against doing so. These results were achieved at the cost of a 10% incidence of symptomatic radiationrelated necrosis and a 5% incidence of permanent new deficits related to radiation effect. As expected, predictors of angiographically confirmed obliteration were as follows: small lesion size, favorable shape (a surrogate for fewer isocenters), high margin dose, and no prior embolization. In a multivariate analysis, the only predictor of permanent deficits was unruptured status. Despite the fact that 76% of the lesions had previously bled and more than 98% were symptomatic, only 2 hemorrhages were noted in the posttreatment period (both cases fatal), and only 3 patients had symptoms progression. If one adds these patients, the overall morbidity rate was 7.5% and the mortality rate was 1.0% (8.5% combined). Given that 23% of the lesions were Spetzler-Martin Grade IV or V, 93% were Grade III or worse, and 31% had failed prior surgery or embolization, the results seem quite laudable. The authors conclude that in young patients with ruptured basal ganglia/thalamic AVMs in whom microsurgery is thought to pose a high risk by an experienced surgeon, radiosurgery is a reasonable alternative. I would concur, but ask a simple question: what is the definition of “experienced” when it comes to microsurgical treatment of basal ganglia and thalamic AVMs? I suspect that even busy surgeons in large cerebrovascular referral centers will not operate on more than 1 or 2 of these lesions a year and that surgeons associated with even the busiest radiosurgical units may operate on no more than 5 in a lifetime. Therefore, I suspect the truth, in most practice settings, is actually the reverse of what Cheng and colleagues propose. The first question asked is not, “Is this basal ganglia/thalamic AVM good for an ‘experienced microsurgeon?’” but rather, “Is it small enough and round enough that we’ll be able to get 20 Gy on the margin without causing a major radiation-induced deficit, and, if not, can we shrink the lesion with embolization to get it to that size and potentially obliterate the bleed site at the same time?” The data presented here do not necessarily invalidate this real-world approach, but they do not give us as much guidance as we’d like. For example, while there was a lower obliteration rate in the 38 patients treated with preradiosurgical embolic agents, the hemorrhage rate was far lower than what natural history studies would predict, given that 42% of patients were incompletely protected. Future prospective multicenter efforts will be needed if we are to ever really understand what is the best treatment for lesions so heterogeneous and rare, especially when the treatments are so dependent on user skill and experience and ongoing technological improvements. (http://thejns.org/doi/abs/10.3171/2011.10.JNS111419)

Long-term results of Gamma Knife surgery for optic nerve sheath meningioma

The goal of this study was to assess the long-term results of Gamma Knife surgery (GKS) in patients harboring an optic nerve sheath meningioma (ONSM). Thirty patients harboring an ONSM were treated with GKS between 1998 and 2003. Gamma Knife surgery was performed as the sole treatment option in 21 of these patients and resection had been performed previously in 9 patients. The mean volume of the tumor at the time of GKS was 3.6 cm(3) (range 1.4-9.7 cm(3)), and the mean prescription peripheral dose was 13.3 Gy (range 10-17 Gy). The mean number of isocenters used to treat these lesions was 8 (range 5-14 isocenters). At a median follow-up of 56 months, visual acuity improved in 11 patients, remained stable in 13 patients (including 4 patients who were completely blind before GKS), and deteriorated in 6 patients. Follow-up images were available in all patients and showed tumor regression in 20 patients and stable tumor in 8 patients. Persistent imaging evidence of progression was only present in 2 patients. With the exception of reversible conjunctival edema in 4 cases, no other serious acute side effect was observed. Gamma Knife surgery provides long-term tumor control for ONSM. The results of this study add substantial evidence that GKS may definitely become a standard treatment approach in selected cases of ONSM.

Gamma Knife surgery as sole treatment for multiple brain metastases: 2-center retrospective review of 1508 cases meeting the inclusion criteria of the JLGK0901 multi-institutional prospective study

The authors retrospectively reviewed the results of Gamma Knife surgery (GKS) used as the sole treatment for brain metastases in patients who met the eligibility criteria for the ongoing JLGK0901 multi-institutional prospective trial. They also discuss the anticipated results of the JLGK0901 study. Data from 1508 consecutive cases were analyzed. All of the patients were treated at the Gamma Knife House of Chiba Cardiovascular Center or the Mito Gamma House of Katsuta Hospital between 1998 and 2007 and met the following JLGK0901 inclusion criteria: 1) newly diagnosed brain metastases, 2) 1-10 brain lesions, 3) less than 10 cm(3) volume of the largest tumor, 4) no more than 15 cm(3) total tumor volume, 5) no findings of CSF dissemination, and 6) no impairment of activities of daily living (Karnofsky Performance Scale score < 70) due to extracranial disease. At the initial treatment, all visible lesions were irradiated with GKS without upfront whole-brain radiation therapy. Thereafter, gadolinium-enhanced MR imaging was performed every 2-3 months, and new distant lesions were appropriately retreated with GKS. Patients were divided into groups according to numbers of tumors: Group A, single lesions (565 cases); Group B, 2-4 tumors (577 cases); and Group C, 5-10 tumors (366 cases). The differences in overall survival (OS) were compared between groups. The median age of the patients was 66 years (range 19-96 years). There were 963 men and 545 women. The primary tumors were in the lung in 1114 patients, gastrointestinal tract in 179, breast in 105, urinary tract in 66, and other sites in 44. The overall mean survival time was 0.78 years (0.99 years for Group A, 0.68 years for Group B, and 0.62 years for Group C). The differences between Groups A and B (p < 0.0001) and between Groups B and C (p = 0.0312) were statistically significant. Multivariate analysis revealed significant prognostic factors for OS to be sex (poor prognostic factor: male, p < 0.0001), recursive partitioning analysis class (Class I vs Class II and Class II vs III, both p < 0.0001), primary site (lung vs breast, p = 0.0047), and number of tumors (Group A vs Group B, p < 0.0001). However, no statistically difference was detected between Groups B and C (p = 0.1027, hazard ratio 1.124, 95% CI 0.999-1.265). The results of this retrospective analysis revealed an upper CI of 1.265 for the hazard ratio, which was lower than the 1.3 initially set by the JLGK0901 study. The JLGK0901 study is anticipated to show noninferiority of GKS as sole treatment for patients with 5-10 brain metastases compared with those with 2-4 in terms of OS.

Gamma Knife surgery for optic glioma

Optic pathway/hypothalamic gliomas represent approximately 2%-5% of brain tumors in children. Total excision, subtotal excision, subtotal excision followed by irradiation, radiation therapy alone, chemotherapy, and no treatment at all have been reported. In this article the authors discuss the results of Gamma Knife surgery (GKS) for optic gliomas in 2 children. Two pediatric patients, a boy and a girl, underwent GKS for optic gliomas at our hospital between March 2005 and August 2005. The children's ages were 10 and 16 years at presentation. The histological diagnosis was confirmed to be pilocytic astrocytoma in both cases. The tumor involved the optic chiasm in 1 patient and the right optic nerve in the other patient. Treatments were planned with the prescription of 11 Gy to the 50% isodose line for the optic chiasm glioma and 15 Gy to the 50% isodose line for the optic nerve glioma. In both patients, GKS was well tolerated. The follow-up periods were 60 and 55 months. Complete response with near-total disappearance of the tumors was observed in both patients. During the follow-up period, neither of the patients developed any endocrine dysfunction. Gamma Knife surgery permits treatment of optic glioma with good tumor control and no clinically relevant morbidity. With the ability to deliver a high dose to the tumor while sparing normal brain tissue, especially the optic nerve, optic chiasm, and pituitary gland, GKS should be the choice of treatment for optic gliomas. A larger number of patients and long-term follow-up are required for further evaluation of the efficacy and potential side effects of GKS.

Gamma Knife surgery for metastatic brain tumors

The authors compared results of Gamma Knife surgery (GKS) for brain metastases obtained at 2 institutions in Japan. They analyzed a consecutive series of 2390 patients with brain metastases who underwent GKS from 1998 through 2005 in 2 institutes (1,181 patients in Chiba; 1,209 in Mito). In the 2 facilities, 1 neurosurgeon each was responsible for diagnosis, patient selection, GKS procedures, and follow-up (T.S. in Chiba, M.Y. in Mito). Even if tumor numbers exceeded 4, all visible lesions were irradiated with a total skull integral dose (TSID) of <or= 10-12 J. No prophylactic whole-brain radiotherapy (WBRT) was applied. If new distant lesions were detected, salvage GKS was appropriately performed. The distributions of patient and treatment factors did not differ between institutes. The most common primary tumors were lung cancer (1,572 patients), followed by gastrointestinal tract (316), breast (211), kidney (113), and other cancers (159). The median survival periods were 7.7 months in Chiba and 7.0 months in Mito (p = 0.0635). The significant poor prognostic factors for overall survival were active extracranial disease status, male sex, and low initial Karnofsky Performance Scale score on multivariate analysis (all p < 0.0001). The neurological survival rates at 1 year were 86.6% in Chiba and 84.2% in Mito (p = 0.3310). This 2-institute study demonstrated no significant institutional differences in any of the treatment result items. Gamma Knife surgery for brain metastases without prophylactic WBRT prevents neurological death and allows a patient to maintain good brain condition. However, there is 1 important patient selection criterion: regardless of how many tumors there are, all lesions can be irradiated with a TSID of <or=12 J.

Long-term results of Gamma Knife surgery for arteriovenous malformations: 10- to 15-year follow up in patients treated with lower doses

Several adverse effects such as brain edema, necrosis, arterial stenosis, hemorrhage after obliteration, and delayed cyst formation have been reported as early and late complications of Gamma Knife surgery (GKS) for arteriovenous malformations (AVMs). These adverse effects seem to be decreased in a lower-dose treatment regimen compared with the classic higher margin doses of 25 Gy because the radiation insult to the surrounding tissue is minimized. Long-term results of lower-dose GKS for AVMs are presented. One hundred fourteen patients with AVMs were treated with lower-dose GKS (< or = 20-Gy margin dose). There were 68 male and 46 female patients, aged 10 to 68 years (mean 35.4 years). The evaluation of AVM nidi and dose planning were performed using both angiography and MR imaging in all cases to exclude the surrounding brain tissue. The mean margin dose was 19.5 Gy. Total angiographically documented obliteration was achieved in 65 (85.5%) of 76 patients. Eleven patients underwent a second treatment, including staged treatment for large AVMs; total AVM obliteration has been achieved in six of them to date. Of 38 patients in whom no follow-up examination could be performed, 19 of them were healthy and 10 were lost from follow up. Nine patients experienced bleeding during the latency period, and four of them suffered lethal hemorrhage. Symptomatic early complications were extensive brain edema after repeated GKS in one patient and an adverse effect on the internal capsule in one. Delayed cyst formation was found in one patient as a late complication 10 years after treatment. No treatment-related death has been noted to date. Lower-dose GKS is an effective and safe treatment for patients with AVMs and may decrease long-term adverse effects to the surrounding brain.

Long-term outcomes after Gamma Knife surgery for vestibular schwannomas: a 10-year experience

The authors sought to assess the results of Gamma Knife surgery (GKS) in patients with vestibular schwannomas (VSs). Seventy-four consecutive patients (33 men and 41 women) were evaluated by means of serial imaging studies, clinical examinations, and questionnaires. Nineteen patients had undergone resection of their VS. Facial nerve function was normal in 63 patients (85.1%) before GKS, and 63.5% of them had useful hearing. The prescription peripheral dose varied between 10 and 14 Gy (mean 12.27 +/- 0.96 Gy); the corresponding central dose was 21 to 30 Gy (mean 24.9 +/- 2.18 Gy). The mean volume of the tumor at GKS was 10.79 +/- 5.52 ml (range 0.11-27.8 ml). A mean of eight isocenters (range 3-17) was used for treating these lesions. At a median follow-up period of 68.3 months (range 30-122 months), tumor shrinkage was observed in 60 patients (81.1%), and the tumor size was stable in 11 (14.8%). Persistent neuroimaging demonstrated evidence of progression in only three patients (4.1%): two underwent repeated GKS after an interval of 18 months and one continues to be observed. Five patients experienced trigeminal dysfunction: in three the dysfunction was transient and in the other two the dysfunction persists. Three patients suffered facial palsy. Useful hearing was preserved in 34 patients. Thirteen patients experienced some degree of hearing improvement. Deterioration of hearing was found in 13 of 62 patients who had Class I or II hearing before treatment. Gamma Knife surgery prevents tumor growth; it achieves excellent neurological function preservation and produces few treatment-related complications.

Gamma Knife surgery for low-grade astrocytomas: evaluation of long-term outcome based on a 10-year experience

The authors report the long-term treatment results of Gamma Knife surgery (GKS) for patients with low-grade astrocytomas who underwent surgery at a single institution. A series of 21 patients (median age 20 years) with 25 intracranial low-grade astrocytomas (World Health Organization Grades I and II) were treated with GKS between 1993 and 2003. Among them, four underwent GKS as a primary treatment. Two underwent GKS as a treatment boost after radiotherapy. In the other 15 patients, GKS was performed as an adjuvant or salvage treatment for residual/recurrent tumors after the patients had undergone craniotomy. Tumor volumes ranged from 0.2 to 13.3 ml (median 2.4 ml). Prescription margin doses ranged from 8 to 18 Gy (median 14.5 Gy). Radiation volumes were 1.3 to 21.6 ml (median 3.6 ml). Patients underwent regular follow up, with neurological evaluation and magnetic resonance imaging studies obtained at 6-month intervals. One patient was lost to follow-up. The clinical follow-up time was 5 to 144 months (median 67 months). Complete tumor remission was seen in three patients. The 10-year progression-free patient survival rate after GKS was 65%. Tumor progression was found in six patients of whom five received further salvage treatment. All the tumor progression occurred within the GKS-treated volumes. Mild-to-moderate adverse radiation effects (AREs) were found in eight patients. Both of the patients who had undergone GKS as a treatment boost after radiotherapy developed AREs, but with good shrinkage of tumors. Gamma Knife surgery provides durable long-term local tumor control with acceptable toxicity for some patients with highly selected low-grade astrocytomas.

Stereotactic radiosurgery for metastatic tumors in the pituitary gland and the cavernous sinus

Metastases to the pituitary gland and cavernous sinus occasionally occur. Metastases of this nature are problematic because they are adjacent to eloquent structures such as cranial nerves, including the optic pathways and nerves for extraocular movement and facial sensation. Stereotactic radiosurgery has been reported to be safe and effective for metastases in various sites of brain parenchyma, providing the tumors are not large. Radiosurgery can be performed to treat a precisely defined target, and the risk of radiation side effects on the surrounding structures is reduced. The results of Gamma Knife surgery (GKS) for the treatment of metastases in the pituitary gland and the cavernous sinus are evaluated. Among 623 patients with brain metastases treated by GKS, 13 patients (2.1%) had pituitary and/or cavernous metastases. The primary malignancies included lung cancer (five cases), breast cancer (two cases), parotid cancer (two cases), renal cell carcinoma, thyroid cancer, nasal cancer, and gastrointestinal stromal tumor (one case each). The location of the tumors was the pituitary gland (Type 1) in four patients, the cavernous sinus (Type 2) in five patients, and both the cavernous sinus and the sellar region (Type 3) in four patients. The patients' symptoms included dysfunction of the pituitary gland (two patients), visual disturbance (four patients), oculomotor palsy (one patient), abducent palsy (five patients), and trigeminal dysfunction (five patients). A margin dose of 12 to 12.3 Gy was delivered to pituitary metastases. A margin dose of 14.4 to 20 Gy was delivered to cavernous lesions. The dose selection depended on the spatial relationship between tumors and the cranial nerves. Imaging and clinical follow-up data have been obtained in nine of 13 patients for 2 to 12 months (median 4 months) after GKS. Three pituitary and/or cavernous tumors are stable in size, and six tumors have disappeared or decreased in size; full or partial improvement of visual function, extraocular movement, and facial sensation have been achieved in these six patients. These preliminary results seem to indicate that GKS is a safe and effective treatment for pituitary and cavernous metastases, as it is effective for parenchymal metastases and promptly improved some patients' symptoms.

Gamma Knife surgery for metastatic brain tumors from renal cell carcinoma

The authors evaluated the results of Gamma Knife surgery (GKS) for the treatment of metastatic brain tumors from renal cell carcinoma (RCC). The authors conducted a retrospective review of the clinical characteristics and treatment outcomes in 69 patients with metastatic brain tumors from RCC who underwent GKS at the authors' institution. Fifty-one patients were men, and 18 were women. The mean patient age was 64.2 years (range 45-85 years). The 69 patients underwent a total of 104 GKS procedures for treatment of 314 tumors. Eighteen patients received repeated GKS. Follow-up magnetic resonance (MR) imaging was used at a mean of 7.1 months after GKS to evaluate the change in 132 tumors after treatment. The mean prescription dose at the tumor margin was 21.8 Gy. The tumor growth control rate was 82.6%. Tumor volume and the delivered peripheral dose were significantly correlated with tumor growth control on univariate and multivariate analyses. Sixty (45.5%) of the 132 tumors assessed with MR imaging were associated with apparent peritumoral edema at the time of GKS. After treatment, peritumoral edema disappeared in 27 tumors, decreased in 13, was unchanged in 16, and progressed in four. Newly developed peritumoral edema after GKS was rare. The delivered peripheral dose was significantly correlated with control of peritumoral edema. The overall median survival time after GKS was 9.5 months. In this study, 34 patients died of systemic disease and 10 died of progressive brain metastases. Multivariate analysis showed that the number of lesions at the first GKS, the Karnofsky Performance Scale score at the first GKS, the recursive partitioning analysis classification, and the interval from diagnosis of RCC to brain metastasis were significantly correlated with survival time. Gamma Knife surgery is effective for metastatic brain tumors from RCC. The disappearance rate of tumors is relatively low, but growth control is high. The delivered dose to the tumor margin is significantly correlated with the control of peritumoral edema. Gamma Knife surgery should be used as the initial treatment modality, if possible, even in patients with multiple metastases. Repeated GKS is recommended for newly developed brain metastases because of the low sensitivity of RCC to conventional radiation therapy.

Long-term results of gamma knife surgery for the treatment of craniopharyngioma in 98 consecutive cases

The authors analyzed the long-term outcomes of gamma knife surgery (GKS) for residual or recurrent craniopharyngiomas after microsurgery and the effects of dose reduction. A total of 107 patients with craniopharyngiomas were treated with GKS at Komaki City Hospital during the past 12 years, and 98 patients were followed up for 6 to 148 months (mean 65.5 months). The mean tumor diameter and volume were 18.8 mm and 3.5 ml, respectively. These tumors were treated with a maximal dose of 21.8 Gy and a tumor margin dose of 11.5 Gy by using a mean of 4.5 isocenters. Final overall response rates were as follows: complete response 19.4%, partial response 67.4%, tumor control 79.6%, and tumor progression 20.4%. Reducing the tumor margin dose resulted in decreased therapeutic response and increased tumor progression, although the rate of visual and pituitary function loss also decreased. Among the factors examined, age (for adults) and the nature of the tumor (cystic or mixed) were statistically significant favorable and unfavorable prognostic factors, respectively. The actuarial 5- and 10-year survival rates were 94.1 and 91%, respectively. The progression-free survival rates were 60.8 and 53.8%, respectively. Patient outcomes were reportedly excellent in 45 cases, good in 23, fair in four, and poor in three; 16 patients died. Deterioration both in vision and endocrinological functions were documented as side effects in six patients (6.1%). Stereotactic GKS is safe and effective, in the long term, as an adjuvant or boost therapy for residual or recurrent craniopharyngiomas after surgical removal and has minimal side effects. New treatment strategies must be devised to manage these tumors.