Neurosurgical applications of radiotherapy

The term ‘radiosurgery’ (RS) indicates a high precision localized technique of irradiation used as an alternative to surgical excision in patients with malignant or benign conditions, both in the brain and in the body. Brain RS has been historically identified with ‘stereotactic radiotherapy’. The term refers to the long-established neurosurgical technique of localizing the position of a lesion in the brain by using a system of external 3D co-ordinates coupled with rigid head immobilization device (often fixed to the skull). A high dose of radiation is delivered to the target stereotactically identified and a safe and accurate treatment is achieved, minimizing the dose of radiation to the surrounding brain. While for some techniques the traditional stereotactic localization has been replaced by the integration of modern imaging with non-invasive accurate immobilization, the term ‘stereotactic’ is still maintained in the clinical practice. Over the past 30 years, the implementation of powerful diagnostic imaging devices and of new radiotherapy equipment has contributed to the large diffusion of brain RS. RS plays an important role in the management of brain tumours, vascular and functional brain lesions and the expertise of the multidisciplinary treating team (clinical oncologists, neurosurgeons, neuro-radiologists and medical physics) contributes to the treatment success rate.     

Gamma knife radiosurgery for intraventricular meningiomas

Purpose  Intraventricular meningiomas are relatively rare tumors that may benefit from stereotactic radiosurgery as a minimally invasive treatment strategy. We report our experience using gamma knife radiosurgery (GKR) for intraventricular meningiomas. Methods  Over a 16-year period, we identified 9 patients with intraventricular meningiomas who were eligible for GKR out of a total management experience of 1,045 patients. The mean patient age was 51 years (range, 14 to 81). Three had radiosurgery for recurrent tumors after prior resection, and GKR was used as an adjunctive after subtotal resection in 1 patient. In the other 5 patients, GKR was used as primary management. Two had a diagnosis of meningioma confirmed by biopsy. The median tumor volume at GKR was 3.9 cc (range, 0.8–11.8). A median margin dose of 16.0 Gy (range, 14.0–22.5) was delivered to the tumor margin. Results  The average follow-up was 64 months. None of the patients developed hydrocephalus or treatment-related morbidity. The progression-free periods after radiosurgery varied from 7 to 160 months (mean, 60). Four tumors regressed and 2 remained unchanged. Three patients showed delayed tumor progression. Meningioma growth control was obtained in 7 out of 9 patients, but 1 patient required two radiosurgical procedures. Conclusions  Gamma knife radiosurgery may be an additional minimally invasive management option for small intraventricular meningiomas in patients who either fail or are unsuitable for resection.     

Radiosurgery of Intracranial Cavernous Malformations

Summary.  Background: The efficacy of radiosurgery in cases of surgically high risk symptomatic cavernous malformations (CMs) for reducing haemorrhagic risk and for seizure control has not been clearly documented and the radiation-induced complications of radiosurgery remain problematic. The authors present a retrospective clinical analysis of 22 cases of CMs treated by radiosurgery.  Methods: Twenty-two patients with symptomatic CMs were treated by linear accelerator (LINAC) radiosurgery or Gamma knife (GK) between 1995 and 1998. Medical records including radiological investigations were carefully reviewed to the last follow-up. The mean age of the patients was 34.1 years (12–56) and the male to female ratio was 12:10. Twenty patients reported at least one episode of bleeding and four had undergone microsurgery before radiosurgery. The remaining two patients presented with seizure without evidence of recent haemorrhage. In 16 cases, the CMs were deep-seated, and the others were located in the cerebral hemispheres; four were located at an eloquent area. LINAC radiosurgery using computed tomography scan was performed in 11 cases until May 1997, after which GK radiosurgery using magnetic resonance (MR) image was performed in 11 cases. The volume of the lesion ranged from 0.09 cc to 4.8 cc (mean 1.42 cc) and the mean marginal dose was 16.1 Gy (8–24). The median follow-up period after radiosurgery was 38.3 months (21–67). The rate of haemorrhage, seizure, and neurological deterioration following radiosurgery was analyzed, and the rate of haemorrhage was compared to that seen in natural course reports.  Findings: There was one case of haemorrhage during the follow-up period and the seizure was well controlled with anticonvulsants. In the group with prior haemorrhage, the bleeding rate of cavernous malformation after radiosurgery (1.55%/year) was lower than that of pre-radiosurgical period (35.5%/year, t=1.296, P=0.04). Six patients showed neurological deterioration following radiosurgery, however, the neurological deficits persisted in only two of the patients with LINAC. The radiosurgical modality (LINAC vs. GK) showed a possible correlation to radiation induced neurological deficits (P=0.06). On the MR images at the last follow-up, the lesion was decreased in eleven patients, increased in one, and no change was found in 10 cases. The T2 weighted MR images revealed a perilesional high signal change in nine patients. This signal change was not statistically related to lesion size (P=0.236), location (P=0.658), nor radiation dose (P=0.363), but was dependent on the treatment modality (P=0.02). New-enhancing lesion and a new cyst were each found in one case, respectively, during the follow-up.  Interpretation: Radiosurgery may be a good alternative option for treatment of surgically high risk CMs. However, the optimal radiosurgical technique, dose adjustment, and proper delineation of the mass are prerequisites. Radiosurgery induced complications are still problematic and post-radiosurgery MR image changes need to be further elucidated. Published online September 2, 2002 Acknowledgment  This work was partly supported by grants from the Clinical Research Institute, Seoul National University Hospital. Correspondence: Dong Gyu Kim, M.D., Department of Neurosurgery, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea.     

Gamma-knife radiosurgery in the treatment of trigeminal schwannomas

Summary Background. Trigeminal nerve schwannomas account for 0.07%–0.28% of all intracranial tumours. Advances in skull base surgery have led to more aggressive resection of these tumours, but surgery may associated with development of new neurological deficits. Methods. In this report, we analyse the long-term results 15 patients with newly diagnosed or residual/recurrent trigeminal schwannoma who underwent gamma-knife treatment. Findings. During a mean 61 months of follow-up, MRI revealed reduction of tumour size in 13 and no size change in 2 patients. The tumour growth control rate was 100% and only 1 patient had transient facial numbness and diplopia. Conclusions. For patients with small to moderate size trigeminal schwannomas, gamma-knife radiosurgery is associated with good tumour control and a minimal risk of adverse radiation effects.     

Long-Term Outcome of Gamma Knife Radiosurgery for Vestibular Schwannoma

Objective We evaluated the long-term outcome of vestibular schwannoma (VS) treated with gamma knife radiosurgery (GKRS) as a primary treatment as well as an adjunct therapy. Materials and Methods We performed a retrospective review (2000–2012) of 82 patients with VS who received GKRS. Of 82 patients, 20 patients with prior resection received GKRS treatment as an adjunct therapy. The remainder of the patients (62) received GKRS as a primary treatment. Results GKRS for VS showed significant variations in tumor growth control (decreased in 44 patients [54%], arrested growth in 30 patients [36%], and increased tumor size in 8 patients [10%]). Progression-free survival rates after GKRS at 3, 5, and 10 years were 98%, 95%, and 95%, respectively. Hearing, facial nerve function, and Karnofsky performance scale were significantly improved after GKRS compared with pretreated status (79 versus 90). Two patients (2.5%) required resection again due to tumor progression and worsening of signs and symptoms. Conclusion Long-term follow-up demonstrated that GKRS offers a high rate of tumor control, preservation of multiple nerve functions, and a good quality of life in both new and recurrent patients with VS.     

Effect of gamma knife irradiation on relaxation and contraction responses of the common carotid artery in the rat

Summary This report concerns a pilot study of the short- and long-term effects of gamma knife radiosurgery on vascular responses. The investigation was carried out on male Sprague-Dawley rats, and the relaxation and contraction responses of the right common carotid artery (CCA) were assessed following irradiation (100 Gy). The non-treated CCA of the same animals served as internal controls. Non-irradiated rats were used to control the effect of normal aging on vascular function. Isometric tension was determined on in vitro preparations of arterial rings. Acetylcholine-mediated, endothelium-dependent relaxation was impaired one month after radiosurgery, as was endothelium-independent relaxation induced by sodium nitroprusside, but the effect on the latter was minimal. The irradiated CCA was also impaired with respect to contraction responses induced by norepinephrine, endothelin-1 or phorbol dibutyrate. This impairment appeared to be biphasic, as it was evident one day after radiosurgery, followed by a partial recovery one week later, and again manifest after one month. At the light microscope level, the carotid arteries appeared to be well preserved throughout the experiment. However, obvious ultrastructural changes were noted in endothelial and smooth muscle cells of specimens obtained three months after radiosurgery. The present data indicate that high dose gamma knife radiosurgery affects the functions of both, the vascular endothelium and the vascular smooth muscles in an apparent time-dependent fashion. Because of its increasing application to patients, there is the need for studying the effects of gamma knife radiosurgery on cerebral arteries, since functional vascular changes may occur in the absence of obvious histological alterations. Our results on CCAs point to the feasibility of such experimental investigations.     

Stereotactic Radiosurgery for Hemangioblastomas of the Brain

Summary  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.     

Gamma Knife Radiosurgery for Glomus Jugulare Tumours

Summary  The aim of this clinical study was to determine the tumour control rate, clinical outcome and complication rate following gamma knife treatment for glomus jugulare tumours. Between May 1992 and May 1998, 13 patients with glomus tumours underwent stereotactic radiosurgical treatment in our department. The age of these patients ranged from 21 to 80 years. The male : female ratio was 2 : 11. Six patients had primary open surgery for partial removal or recurrent growth and subsequent radiosurgical therapy. Radiosurgery was performed as primary treatment in 7 cases. The median tumour volume was 6,4 cm³ (range: 4,6–13,7 cm³). The median marginal dose applied to an average isodose volume of 50% (30–50%) was 13,5 Gy (12–20 Gy). In 10 patients, a total of 48 MRI and CT follow-up scans were available. The remaining three patients have been excluded from the postradiosurgical evaluation since the observation time (t<12 months) was too short or patients were lost to follow up. The median interval from Gamma Knife treatment to the last radiological follow-up was 37,6 months (5–68 months). In 4 patients (40%) decreased tumour volumes were observed and in 6 cases (60%) the tumour size remained unchanged. Neurological follow-up examinations revealed improved clinical status in 5 patients (50%), a stable neurological status in 5 patients (50%) and no complications occurred. According to our preliminary experience Gamma Knife radiosurgery represents an effective treatment option for glomus jugulare tumours.     

伽玛射线立体定向放射外科治疗原发性三叉神经痛效果的Meta分析

目的 分析伽玛射线立体定向放射外科治疗原发性三叉神经痛的疗效.方法 检索数据库中近年来关于伽玛射线立体定向放射外科治疗原发性三叉神经痛的文献,对搜索结果进行筛选和分析.结果 术后疼痛缓解率（符合BNI Ⅰ～Ⅲ）为36.1％～94.0％,平均有效率77.3％.缓解时间平均需45 d（1 ～495 d）,复发率18％ ～ 42.9％,平均复发时间最短为9.6个月,最长为4.4年.并发症包括面部麻木（3.6％～43.0％）,感觉减退（2.5％）等.结论 伽玛射线立体定向放射外科治疗原发性三叉神经痛疗效肯定,并发症相对可控,其疗效和并发症与治疗剂量、靶点位置、数量等因素有关.     

原发性三叉神经痛的伽玛刀治疗

目的 评价伽玛刀治疗原发性三叉神经痛的疗效。方法 72例原发性三叉神经痛采用伽玛刀治疗,靶点为三叉神经根近脑干段,4mm准直器,中心剂量(70—80)Gy。结果 随访2年以上5l例,治愈39例(76．5％),有效7例(13．7％),无效5例(9．8％)。19例(37．3％)出现一过性轻度面部麻木,感觉减退,无其它并发症。结论 伽玛刀治疗原发性三叉神经痛疗效确切,无严重并发症。     

Gamma knife surgery for craniopharyngioma

Summary We present our results of Gamma Knife surgery for craniopharyngioma in nine patients. The current status of surgery, radiation therapy, intracavitary instillation of radionucleides and Gamma Knife surgery in the management of craniopharyngiomas is discussed.     

伽玛刀治疗分泌型垂体腺瘤120例分析

目的评价伽玛刀作为首选方法治疗分泌型垂体腺瘤的疗效。方法回顾性分析1995年7月至2003年12月应用伽玛刀作为首选治疗120例分泌型垂体瘤患者的临床资料。治疗等剂量曲线45％～70％、周边剂量15～32Gy（平均28．5Gy）,中心剂量为35～70Gy（平均45．5Gy）,靶点165个（平均1～3个）。结果120例患者中111例获得随访,随访时间12～72个月,平均36个月。随访病例内分泌激素水平控制率为48．6％;肿瘤生长控制率96．2％;垂体功能低下发生率为2．7％;肿瘤卒中发生率0．9％。结论伽玛刀作为首选治疗分泌型垂体腺瘤安全、有效,肿瘤生长控制良好。     

Gamma Surgery for Hemangiopericytomas

A retrospective analysis of a consecutive series of 12 patients with 15 intracranial hemangiopericytomas treated at the University of Virginia using Gamma surgery is presented. Clinical and radiographic follow up of 3 to 56 months is available for 10 patients with 12 tumors. There was one tumor present at the time of initial Gamma surgery in each patient. Two new tumors occurred in patients previously treated. Nine of the tumors decreased in volume and three remained stable. Four of the nine tumors that shrank later progressed at an average of 22 months after treatment. Of the tumors that decreased in volume and have not progressed, the response has been for an average of 11 months. The follow-up for two tumors that remained unchanged was 10 and 34 months (average 22 months). A third tumor was unchanged at 42 months but the patient died of new disease adjacent to the treated area in the anterior skull base. There were no complications and the quality of life following the procedure was maintained or improved in every case. Gamma surgery is effective in palliating the patients by decreasing tumor volume and delaying recurrence.     

Successful Management of a Catecholamine-Secreting Glomus Jugulare Tumor with Radiosurgery Alone

Secretory glomus jugulare tumors are often resected surgically to control the systemic effects of the catecholamines they produce. This involves complex skull base surgery, which carries significant risks and frequent morbidity. Stereotactic radiosurgery (SRS) is a recently recognized treatment for glomus jugulare tumors, though little is known about its use in secretory tumors. Case Report A young fit patient with a catecholamine-secreting glomus jugulare tumor was treated with SRS alone and over the following 37 months her urinary catecholamine excretion fell to near normal levels, and serial magnetic resonance imaging (MRI) confirmed a reduction in tumor volume. Discussion Radiosurgery is an accepted treatment for glomus jugulare tumors and is now readily available to skull base surgeons. In this case a catecholamine-secreting tumor was successfully controlled with radiosurgery alone. Further research and long-term follow-up will determine the role of this treatment in the nonsurgical management of secreting glomus jugulare tumors.