Gamma Knife Radiosurgery for Central Neurocytomas

Gamma Knife radiosurgery for central neurocytoma: a quantitative systematic review and metanalysis

Central neurocytomas (CN) are rare tumors within the central nervous system. Originating from the septum pellucidum and subependymal cells, they are typically found in the third and lateral ventricles. For this reason, they may lead to hydrocephalus and increased intracranial pressure. CNs are generally benign lesions that exhibit locally aggressive behavior and a high recurrence rate. Complete surgical resection is the preferred treatment; however, due to their anatomical location, this is often not feasible. Based on these findings, Gamma Knife radiosurgery (GKRS) has been introduced for managing both residual and recurrent tumors and as an initial therapy in selected cases. This study aimed to systematically review the available knowledge regarding GKRS for CN. A systematic investigation of the scientific literature was undertaken through an exhaustive search across prominent databases, including PubMed, Web of Science, and Google Scholar, by employing precise MeSH terms such as "Central neurocytoma," "Radiosurgery," "Gamma Knife," and "Stereotactic Radiosurgery." A comprehensive quantitative systematic review and meta-analysis were meticulously conducted, focusing on cases of CN treated with GKRS for a thorough evaluation of outcomes and efficacy. Seventeen articles, including 289 patients, met the inclusion criteria. Random effects meta-analysis estimates for disease control and local tumor control were 90% (95% CI 87-93%; I2 = 0%, p < 0.74) and 94% (95% CI 92-97%; I2 = 0%, p < 0.98), respectively. When considering only studies with at least 5 years of follow-up, progression-free survival was 89% (95% CI 85-94%; I2 = 0.03%, p < 0.74). The mean clinical control rate was 96%. This systematic review and meta-analysis confirmed the safety and efficacy of GKRS in managing CN.

Clinical prognostic factors for central neurocytoma and subgroup analysis of different treatment measures: A SEER database-based retrospective analysis from 2003 to 2019

Purpose

The study aimed to identify clinical prognostic factors affecting overall survival (OS) in patients with central neurocytoma (CN) and to determine independent prognostic factors in the subgroups of different treatment modalities using a retrospective analysis based on the SEER database from 2003 to 2019.

Materials and methods

Data regarding patients with CN, including basic clinical characteristics, treatment measures, and prognosis follow-up, were extracted from the SEER database. The prognostic variables for all patients were assessed using log-rank test as well as univariate and multivariate analyses based on the Cox proportional hazards model. The same statistical methods were used for analysis in different subgroups of gross total resection (GTR), subtotal resection (STR), no surgery, radiotherapy (RT), and no RT.

Results

In total, 413 patients were enrolled in this study. Tumor size, primary site surgery, and RT were independent prognostic factors in all patients with CN. In subgroup analyses, RT was not an independent prognostic factor in patients with GTR. However, sex and race were independent prognostic factors in patients with STR. Additionally, tumor size was an independent prognostic factor in patients who did not undergo surgery. Furthermore, sex and primary site were independent prognostic factors in patients who received RT. Size and primary site surgery were independent prognostic factors in patients without RT.

Conclusion

In our study, patients with small tumors or GTR or those who did not receive RT showed a better prognosis. GTR was the preferred treatment for CN. RT was not recommended for patients after GTR. Men and African American showed certain advantages after STR surgery. Tumors with a size of >4 cm were recommended for active treatment. In the RT subgroup, patients with tumors outside the ventricle or women had a poorer prognosis than those with tumors within the ventricle or men, respectively. These findings will help clinicians and patients understand the treatment and prognosis of CN visually and intuitively.

Malignant transformation of central neurocytoma with dissemination 17 years after initial treatment: illustrative case

BACKGROUND

Central neurocytomas usually have a favorable clinical course, and gross total resection (GTR) results in long-term survival. Recurrences of central neurocytomas are usually local, and dissemination is extremely rare.

OBSERVATIONS

A 24-year-old man who presented with vomiting was found to have a mass in the right lateral ventricle. After GTR, he received whole-brain irradiation and chemotherapy and had remained disease-free on follow-up for years. The review of the initial tumor revealed central neurocytoma. Seventeen years later, he presented with deterioration of memory, and magnetic resonance imaging showed an enhanced lesion in the left hippocampus. The enhanced lesion was resected, and the histological examination revealed that the tumor was a disseminated atypical central neurocytoma with frequent mitoses. Although he was treated with chemotherapy, the disseminated tumor slowly grew and invaded the brain. Massive brain invasion occurred without enhanced lesions, and he died 27 months after the tumor recurrence.

LESSONS

In this patient, a central neurocytoma disseminated after an extremely long period of time. Once neurocytomas disseminate and show aggressive behavior, patients usually follow a poor course. Patients with central neurocytomas should be followed up for a long time.

Less common intraparenchymal tumors

The chapter outlines the management of a great variety of rare intraparenchymal tumors. For some like medulloblastomas or ependymomas, GKNS has little to offer. For others like neurocytomas, primary central nervous system lymphomas, and papillary pineal tumors the current findings look most hopeful. For choroid plexus papillomas there is currently not enough information to define the role of GKNS in their treatment. Pineal region tumors are a complex and varied group of neoplasms. Their complexity, variety and ethnic variability means that defining the role of GKNS will require continuing research before a consensus about management can be reached.

Impact of Adjuvant Radiotherapy in Patients with Central Neurocytoma: A Multicentric International Analysis

Simple Summary

Central neurocytoma is a rare tumor accounting for <0.5% of all intracranial tumors. We analyzed 33 patients treated with surgical resection with or without radiotherapy from ten closely cooperating institutions in Germany, Egypt, and Jordan. Patients who received radiotherapy had longer progression-free survival with an acceptable toxicity profile.

Abstract

Background: Central neurocytoma (CN) is a rare tumor accounting for <0.5% of all intracranial tumors. Surgery ± radiotherapy is the mainstay treatment. This international multicentric study aims to evaluate the outcomes of CNs patients after multimodal therapies and identify predictive factors. Patients and methods: We retrospectively identified 33 patients with CN treated between 2005 and 2019. Treatment characteristics and outcomes were assessed. Results: All patients with CN underwent surgical resection. Radiotherapy was delivered in 19 patients. The median radiation dose was 54 Gy (range, 50–60 Gy). The median follow-up time was 56 months. The 5-year OS and 5-year PFS were 90% and 76%, respectively. Patients who received radiotherapy had a significantly longer PFS than patients without RT (p = 0.004) and a trend towards longer OS. In addition, complete response after treatments was associated with longer PFS (p = 0.07). Conclusions: Using RT seems to be associated with longer survival rates with an acceptable toxicity profile.

Gamma Knife radiosurgery as a primary treatment for central neurocytoma

OBJECTIVE

This study was performed to evaluate the role of Gamma Knife radiosurgery (GKRS) as a primary treatment for central neurocytomas (CNs).

METHODS

The authors retrospectively assessed the treatment outcomes of patients who had undergone primary treatment with GKRS for CNs in the period between December 2001 and December 2018. The diagnosis of CN was based on findings on neuroimaging studies. The electronic medical records were retrospectively reviewed for additional relevant preoperative data, and clinical follow-up data had been obtained during office evaluations of the treated patients. All radiographic data were reviewed by a dedicated neuroradiologist.

RESULTS

Fourteen patients were treated with GKRS as a primary treatment for CNs in the study period. Seven patients (50.0%) were asymptomatic at initial presentation, and 7 (50.0%) presented with headache. Ten patients (71.4%) were treated with GKRS after the diagnosis of CN based on characteristic MRI findings. Four patients (28.6%) initially underwent either stereotactic or endoscopic biopsy before GKRS. The median tumor volume was 3.9 cm3 (range 0.46–18.1 cm3). The median prescription dose delivered to the tumor margin was 15 Gy (range 5.5–18 Gy). The median maximum dose was 30 Gy (range 11–36 Gy). Two patients were treated with fractionated GKRS, one with a prescription dose of 21 Gy in 3 fractions and another with a dose of 22 Gy in 4 fractions. Control of tumor growth was achieved in all 14 patients. The median volume reduction was 26.4% (range 0%–78.3%). Transient adverse radiation effects were observed in 2 patients but resolved with improvement in symptoms. No recurrences were revealed during the follow-up period, which was a median of 25 months (range 12–89 months).

CONCLUSIONS

Primary GKRS for CNs resulted in excellent tumor control rates without recurrences. These results suggest that GKRS may be a viable treatment option for patients with small- to medium-sized or incidental CNs.

Gamma Knife radiosurgery for the treatment of central neurocytoma: a single-institution experience of 25 patients

Central neurocytomas (CNs) are extremely rare tumors that account for 0.1-0.5% of all intracranial neoplasms. Recently, Gamma Knife radiosurgery (GKRS) has become a treatment option in patients with CN. We aimed to evaluate the efficacy and safety of GKRS in 25 CN patients and review the results along with relevant literature. GKRS patient database was searched, and 25 patients who underwent GKRS for CN between 2009 and 2018, were evaluated retrospectively. The study cohort included 15 female and ten male patients with a median age of 32 years (range, 5-60). The most common presenting symptom was headache (88%). The neurological examination was unremarkable in all patients, except for one patient with decreased vision. Twenty patients (80%) had a history of surgical resection. Most of the tumors (92%) were located in the ventricles, and the median tumor volume was 4.8 cm³ (range, 0.8-28.1). The median marginal dose was 14 Gy (range, 12-15) to a median isodose of 50% (range, 40-50). Following a median follow-up of 80 months (range, 36-138), local tumor control was achieved in 100% of patients. Distant recurrence was observed in one patient (4%). No adverse radiation effect was observed. Regarding non-specific post-GKRS symptoms, one patient experienced a prolonged headache, and one epileptic patient experienced a brief partial seizure. In our patient cohort, GKRS yielded favorable local tumor control (100%) during a median follow-up of 6.6 years. Our series demonstrates that GKRS is an effective and safe treatment option for patients with primary or residual CNs.

[Choice optimisation of radiation therapy technique for central neurocytomas from literature data]

Neurocytomas represent 0,25 to 0,5 of brain tumours. These tumours have neuronal differentiation. It's a young adult disease. The main treatment is neurosurgery. The place of other therapies is still unclear, noticeably with regards to radiotherapy. This review aim is to determine the place and the modalities of radiotherapy in the management of neurocytomas. A literature search using PubMed allowed to select the most relevant studies. Finally, 22 studies were selected according to pre-established criteria to answer the problem. All studies were retrospective studies except one. The analysis conclusion defined radiotherapy as a treatment of choice in selected patients, when surgical resection was incomplete or when tumour was atypical.

The role of proton beam therapy in central neurocytoma: A single-institution experience

PURPOSE

Central neurocytomas (CNs) are rare World Health Organization grade II tumors managed with surgery and radiation therapy. We report our experience in managing CN with proton beam therapy (PBT) when radiation therapy was used.

METHODS AND MATERIALS

We identified 61 patients with pathologically diagnosed CN treated at our institution between 1996 and 2016, of which 24 met inclusion criteria. Patient, tumor, and treatment characteristics are reported in context of progression-free survival and treatment-related adverse events.

RESULTS

Of 24 patients identified, median age at diagnosis was 21 years (range, 14-60). Median maximal tumor diameter was 4.5 cm (range, 1.4-6.8). Eighteen (75%) patients underwent upfront surgery alone. Sixteen (67%) patients received adjuvant or salvage PBT at a median dose of 54 Gy (relative biological effectiveness). Median follow-up was 56 months. Median progression-free survival (PFS) was 61 months. Eleven patients had disease progression with median time to progression of 22 months. Of the 5 patients with gross total resection, 4 experienced local recurrence and had MIB-1 >4% (range, 4.5-30). There was improved PFS with addition of PBT to definitive surgery (log-rank, P = .06); there was no disease progression to date. In patients who experienced disease recurrence/progression, MIB-1 <4% was associated with improved PFS (log-rank, P = .007). All patients tolerated PBT well with toxicities typical for cranial irradiation and with no grade 3+ toxicities.

CONCLUSION

In our cohort, CN with elevated MIB-1 index were at increased risk for disease progression. However, adjuvant radiation therapy appears to effectively prevent failure. PBT toxicities appear to be comparable to if not less than published photon experiences.

Systematic Analysis of Clinical Outcomes Following Stereotactic Radiosurgery for Central Neurocytoma

Central neurocytoma (CN) typically presents as an intraventricular mass causing obstructive hydrocephalus. The first line of treatment is surgical resection with adjuvant conventional radiotherapy. Stereotactic radiosurgery (SRS) was proposed as an alternative therapy for CN because of its lower risk profile. The objective of this systematic analysis is to assess the efficacy of SRS for CN. A systematic analysis for CN treated with SRS was conducted in PubMed. Baseline patient characteristics and outcomes data were extracted. Heterogeneity and publication bias were also assessed. Univariate and multivariate linear regressions were used to test for correlations to the primary outcome: local control (LC). The estimated cumulative rate of LC was 92.2% (95% confidence interval: 86.5-95.7%, p<0.001). Mean follow-up time was 62.4 months (range 3-149 months). Heterogeneity and publication bias were insignificant. The univariate linear regression models for both mean tumor volume and mean dose were significantly correlated with improved LC (p<0.001). Our data suggests that SRS may be an effective and safe therapy for CN. However, the rarity of CN still limits the efficacy of a quantitative analysis. Future multi-institutional, randomized trials of CN patients should be considered to further elucidate this therapy.

Rapid tumor growth with glial differentiation of central neurocytoma after stereotactic radiosurgery

Although stereotactic radiosurgery (SRS) is effective for central neurocytoma (CN), the long-term outcome of SRS remains unclear. We present a case of recurrent CN that was diagnosed 10years after surgical resection and consecutive stereotactic radiotherapy. The patient was treated with SRS for the recurrent tumor, but underwent two-staged surgery once again due to rapid tumor growth. Histological features of the recurrent tumor were consistent with the diagnosis of CN. However, an increased Ki-67 proliferation index (3.4%), aberrant angiogenesis and glial differentiation of the tumor cells were observed, which were not identified in the initial CN. In addition, vascular endothelial growth factor (VEGF) and VEGF receptor were highly expressed in the recurrent tumor cells, as well as in the vascular endothelial cells. Our case suggests that malignant transition with aberrant angiogenesis and glial differentiation may be attributable to SRS.

Treatment Results of Gamma Knife Radiosurgery for Central Neurocytoma: Report of a Japanese Multi-Institutional Cooperative Study

OBJECTIVE

Central neurocytoma (CN) is a rare benign neuronal tumor, and a limited number of reports have described the usefulness of radiosurgery for a relatively large group of patients. We evaluated the effectiveness and outcomes of Gamma Knife radiosurgery (GKS) for CN in a Japanese multi-institutional study.

METHODS

We performed retrospective analysis of 36 patients with CN who were treated with GKS in 12 institutes in Japan. All patients underwent surgery before GKS. The median tumor volume at GKS was 4.9 mL (range, 0.07-23.4 mL), and the median radiation dose prescribed to the tumor margin was 15 Gy (range, 10-20 Gy). The median follow-up period was 54.5 months (range, 3-180 months).

RESULTS

The local tumor progression-free survival rates at 5 and 10 years were 94% and 86%, respectively. Three patients developed distant dissemination 16-90 months later. Overall progression-free survival was unrelated to the prescribed dose (<15 Gy vs. ≥15 Gy, P = 0.62), tumor size (<6 mL vs. ≥6 mL, P = 0.46), gender (P = 0.36), age (<30 vs. ≥30 years, P = 0.37), target of GKS (residual vs. recurrence, P = 0.90), and type of enhancement (homogeneous vs. inhomogeneous, P = 0.19). Two permanent complications occurred with 1 intratumoral hemorrhage and 1 radiation injury.

CONCLUSIONS

GKS is effective for CN because of its high rate of long-term local tumor control. GKS may have a potential role as a primary treatment for asymptomatic, relatively small tumors in the absence of hydrocephalus without surgical resection.

The management of incidental central neurocytoma

This article elucidates the role of stereotactic radiosurgery for the management of central neurocytoma. This rare intraventricular tumor is usually benign and is best treated with surgical excision if the tumor is large and symptomatic. However, some distinctive neuroimaging features are found in this tumor that help to identify the tumor based on detailed MRI and computed tomography examinations. The cumulative experience shows that single-session radiosurgery using Gamma Knife radiosurgery is an effective and safe alternative treatment of incidental central neurocytoma. After radiosurgery, a serial MRI examination performed every 6 months for long-term follow-up is necessary to monitor radiosurgical response of the tumor.

The management of central neurocytoma: radiosurgery

Stereotactic radiosurgery (SRS) has evolved into a mainstay in the primary and adjuvant management of most intracranial tumors. Central neurocytomas are rare, usually benign, intraventricular tumors that can be challenging to completely resect and often recur. Adjuvant therapy has been suggested for residual or recurrent tumors, especially in the setting of atypical neurocytomas. The limited data available suggest that SRS is a highly effective treatment approach for primary and adjuvant therapy, with tumor control rates of 80% to 90%. Due to its highly conformal and selective nature, SRS avoids the inconvenience and delayed toxicity of conventional radiation therapy.

Therapeutic regimens and prognostic factors of brain metastatic cancers

OBJECTIVE

This work aims to investigate the therapeutic regimen of brain metastatic cancers and the relationship between clinical features and prognosis.

METHODS

Clinical data of 184 patients with brain metastatic cancers were collected and analysed for the relationship between survival time and age, gender, primary diseases, quantity of brain metastatic foci, their position, extra cranial lesions, and therapeutic regimens.

RESULTS

The average age of onset was 59.1 years old. The median survival time (MST) was 15.0 months, and the patients with breast cancer as the primary disease had the longest survival time. Females had a longer survival time than males. Patients with meningeal metastasis had extremely short survival time. Those with less than 3 brain metastatic foci survived longer than patients with more than 3. The MST of patients receiving radiotherapy only and the patients receiving chemotherapy only were all 10.0 months while the MST of patients receiving combination therapy was 16.0 months. Multiple COX regression analysis demonstrated that gender, primary diseases, and quantity of brain metastatic foci were independent prognostic factors for brain metastatic cancers.

CONCLUSIONS

Chemotherapy is as important as radiotherapy in the treatment of brain metastatic cancer. Combination therapy is the best treatment mode. Male gender, brain metastatic cancers originating in the gastrointestinal tract, more than 3 metastatic foci, and involvement of meninges indicate a worse prognosis.

[Radiotherapy in central neurocytoma and review of literature]

Central neurocytoma is a rare primary central nervous system tumour of young adults with good prognosis. Typical and atypical forms are described according to various histologic and histopathologic parameters. Central neurocytoma develops in the periventricular areas and is revealed by increased intracranial pressure. The tumour exhibits typical characteristics on CT scan and MRI and a characteristic peak of glycine on spectroscopy-MRI. The main treatment is total resection, which is achievable only in half of the cases. External beam therapy improves local control of partially resected and/or atypical central neurocytoma. Many studies show that stereotactic radiotherapy can be used in the therapeutic management as exclusive treatment, in postoperatives residues and in case of distant recurrence. Chemotherapy is the last line of treatment in refractory forms, especially in the forms with extracranial and/or neuromeningeal spread and in recurrent forms after treatment with surgery and/or radiotherapy.

Radiosurgery for central neurocytoma: long-term outcome and failure pattern

Despite the favorable outcomes of radiosurgery for central neurocytoma (CN), these results are based on case series that included a limited number of patients and short follow-up periods because of the scarcity of CN. Because CN is a benign tumor with an indolent clinical course, long-term follow-up and analysis of failure pattern are required for the establishment of the role of radiosurgery in the management of CN. Twenty consecutive patients (10 patients who received Gamma Knife radiosurgery (GKRS) as a primary treatment and 10 patients who received GKRS as a secondary treatment) with a radiological follow-up period ≥36 months were included in this study. The mean radiological follow-up duration was 100 months (range 43-149 months). The mean tumor volume was 10.4 cm(3) (range 0.4-36.4 cm(3)) and the mean marginal dose was 15.4 Gy (range 9-20 Gy). Local control failure was found in six patients at the last radiological follow-up. Overall actuarial local control rates were 89.5 % at 5 years and 83.1 % at 10 years. The primary GKRS group included two cases with local failure, with cyst formation or local recurrence. In contrast, in the secondary GKRS group, local control failure was found in four cases (including three cases with an "out-of-field recurrence" pattern) and occurred earlier compared with the primary GKRS group. Our study suggests that GKRS could be a primary or secondary treatment option for CN. However, long-term radiological follow-up is mandatory. In particular, more careful consideration during margin delineation and planning procedure is required in the secondary GKRS group.

Stereotactic radiosurgery for central neurocytoma: a quantitative systematic review

Central neurocytoma was originally described as a rare benign neuronal tumor. However, progression and local recurrences after surgery are well recognized. Stereotactic radiosurgery is another option for treatment of CN. In order to evaluate the efficacy of SRS, we performed a quantitative systematic review of the available data on SRS for CN. To identify eligible studies, systematic searches for all CNs treated with SRS were conducted in major scientific publication databases. English studies published prior to May 2011 were reviewed and summarized with reference to the inclusion and exclusion criteria. Tumor local control was analyzed. Heterogeneity and publication bias were assessed, and the summary control rate and 95%confidence interval (CI) were calculated from the raw data.Of 35 eligible studies, five with a total of 64 CNs were included in this quantitative analysis. Four studies reported a mean or median follow-up time of[60 months. The test of heterogeneity was non-significant among the included studies. Publication bias was observed as indicated by an asymmetric funnel plot. There was non-significance in Begg’s test and Egger’s test. The estimated cumulative rate of neuro-imaging tumor control was 91.1% (95%CI = 80.2–96.3%) at a mean follow-up of 59.3 months(range 6–140 months). The P-value was\0.0001 under a random-effect model. Sensitivity analysis showed a similar summary control rates (89.5–93.7%). Based on the summary local control rate of SRS for CN found in this quantitative analysis, we suggest that single session SRS is an effective and safe alternative therapy for recurrent or residual CN. However, the results of our analysis are limited by the predominance of case series studies due to scarcity of published research. Further randomized trials of CN patients via multicenter consortia should be considered for supplementing the weak points in our quantitative analysis.

[Place of stereotactic techniques in the modern management of lateral ventricle tumors. Stereotactic biopsies and radiosurgery]

The authors make an overview about the use of stereotactic techniques in the management of lateral ventricle tumors. If stereotactic techniques are not in the foreground for the management of lateral ventricle tumors, stereotactic biopsies can be very useful in case of atypical, clinical or radiological presentation of the tumors and radiosurgery can help in case of evolution or re-evolution of tumors after resection. In these cases, stereotactic procedures are very safe. Modern technical evolutions allow the optimization of the stereotactic procedure but also to mix robotic with endoscopic techniques in order to offer new surgical perspectives.

[Central neurocytomas of the lateral ventricle. A series of 35 cases with review of the literature]

Central neurocytoma is the second most frequent tumor in our series of 284 lateral ventricle tumors (12%). Mean age was 32.6 years. There was a male predominance (20/35). Most frequent clinical signs were neuropsychological disturbances and intracranial hypertension. On imaging, these tumors concentrate central calcifications in more than half of cases. Main locations were frontal horn and corpus of lateral ventricle (82%). Uneventful postoperative course was recorded in 52% of cases. Immunoreactivity against neuron-specific enolase (NSE), synaptophysin, S100 protein, Microtubul Associated Protein de type 2 (MAP2) and calcineurin confirms the neuronal nature of the neoplasm. This tumor has a good prognosis. Local control after surgery is obtained in 68% of cases. Gamma knife surgery seems to be useful in cases of little volume with tumoral remnants or recurrence, when radiological appearance is well circumscribed and round-shaped.

Gamma knife radiosurgery for central neurocytoma: retrospective analysis of fourteen cases with a median follow-up period of sixty-five months

OBJECT

Central neurocytoma (CN) is considered to be a benign neuronal tumor with possible atypical behavior. Microsurgery, radiation therapy (RT) and radiosurgery all have been used in treating this rare disease during the past decade. In this study, the authors present the experience with gamma knife radiosurgery (GKRS) on 14 patients with CN during a median follow-up period of 65 months and document the safety and efficacy of GKRS in the treatment of CN.

METHODS

Between November 1997 and December 2009, 14 patients pathologically diagnosed with CN were treated with GKRS. Follow-up magnetic resonance imaging (MRI) was performed at 6-month intervals. Tumor volume and adverse radiation effects (ARE) were documented to evaluate tumor response to GKRS. The Karnofsky Performance Scale (KPS) and neurological status were used to assess clinical outcome. The mean radiation dose prescribed to the tumor margin was 12.1 Gy (ranging from 11 to 13 Gy). The mean tumor volume was 19.6 ml (ranging from 3.5 to 48.9 ml). The mean follow-up period was 70 months (ranging from 30 to 140 months), and the median follow-up period was 65 months.

RESULTS

Tumor shrinkage was found in all patients at the final MRI follow-up. The mean volume reduction was 69% (ranging from 47 to 87%). No tumor progression, ARE or radiation-related toxicity developed in any of the cases. The KPS scores of all patients were the same or had increased, and the neurological functions were all stable without deterioration at the final follow-up.

CONCLUSION

In our observations, GKRS was found to be an effective and safe alternative as adjuvant therapy for pathology-confirmed CN. The tumor volume and functional outcome can be controlled with a favorable result in long-term observation. Compared with RT and microsurgery, GKRS plays an important role in the treatment of CN as a minimally invasive technique with low morbidity. Regular long-term MRI follow-up should be mandatory to document the tumor response and possible recurrence. Multicenter consortia should be considered for further investigation and evaluation of GKRS for such a rare tumor.