Cerebellar pilocytic astrocytoma: a treatment protocol based upon analysis of 73 cases and a review of the literature

Unraveling the signaling mechanism behind astrocytoma and possible therapeutics strategies: A comprehensive review

BACKGROUND

A form of cancer called astrocytoma can develop in the brain or spinal cord and sometimes causes death. A detailed overview of the precise signaling cascade underlying astrocytoma formation has not yet been revealed, although various factors have been investigated. Therefore, our objective was to unravel and summarize our current understanding of molecular genetics and associated signaling pathways with some possible therapeutic strategies for astrocytoma.

RECENT FINDINGS

In general, four different forms of astrocytoma have been identified in individuals, including circumscribed, diffuse, anaplastic, and multiforme glioblastoma, according to a recent literature review. All types of astrocytoma have a direct connection with some oncogenic signaling cascade. Common signaling is MAPK cascade, including Ras-Raf-ERK, up-regulated with activating EGFR/AKT/PTEN/mTOR and PDGFR. Recent breakthrough studies found that BRAF mutations, including KIAA1549: BRAF and BRAF V600E are responsible for astrocytoma progression. Additionally, cancer progression is influenced by mutations in some tumor suppressor genes, such as the Tp53/ATRX and MGMT mutant. As synthetic medications must cross the blood-brain barrier (BBB), modulating signal systems such as miRNA is the primary option for treating patients with astrocytoma. However, available surgery, radiation therapy, and experimental therapies such as adjuvant therapy, anti-angiogenic therapy, and EGFR-targeting antibody drug are the usual treatment for most types of astrocytoma. Similar to conventional anticancer medications, some phytochemicals slow tumor growth by simultaneously controlling several cellular proteins, including those involved in cell cycle regulation, apoptosis, metastatic spread, tyrosine kinase, growth factor receptor, and antioxidant-related proteins.

CONCLUSION

In conclusion, cellular and molecular signaling is directly associated with the development of astrocytoma, and a combination of conventional and alternative therapies can improve the malignancy of cancer patients.

Update for astrocytomas: medical and surgical management considerations

Astrocytomas include a wide range of tumors with unique mutations and varying grades of malignancy. These tumors all originate from the astrocyte, a star-shaped glial cell that plays a major role in supporting functions of the central nervous system (CNS), including blood-brain barrier (BBB) development and maintenance, water and ion regulation, influencing neuronal synaptogenesis, and stimulating the immunological response. In terms of epidemiology, glioblastoma (GB), the most common and malignant astrocytoma, generally occur with higher rates in Australia, Western Europe, and Canada, with the lowest rates in Southeast Asia. Additionally, significantly higher rates of GB are observed in males and non-Hispanic whites. It has been suggested that higher levels of testosterone observed in biological males may account for the increased rates of GB. Hereditary syndromes such as Cowden, Lynch, Turcot, Li-Fraumeni, and neurofibromatosis type 1 have been linked to increased rates of astrocytoma development. While there are a number of specific gene mutations that may influence malignancy or be targeted in astrocytoma treatment, O 6-methylguanine-DNA methyltransferase (MGMT) gene function is an important predictor of astrocytoma response to chemotherapeutic agent temozolomide (TMZ). TMZ for primary and bevacizumab in the setting of recurrent tumor formation are two of the main chemotherapeutic agents currently approved in the treatment of astrocytomas. While stereotactic radiosurgery (SRS) has debatable implications for increased survival in comparison to whole-brain radiotherapy (WBRT), SRS demonstrates increased precision with reduced radiation toxicity. When considering surgical resection of astrocytoma, the extent of resection (EoR) is taken into consideration. Subtotal resection (STR) spares the margins of the T1 enhanced magnetic resonance imaging (MRI) region, gross total resection (GTR) includes the margins, and supramaximal resection (SMR) extends beyond the margin of the T1 and into the T2 region. Surgical resection, radiation, and chemotherapy are integral components of astrocytoma treatment.

Quality indicators for evaluating the 30-day postoperative outcome in pediatric brain tumor surgery: a 10-year single-center study and systematic review of the literature

OBJECTIVE

Surgery is the cornerstone in the management of pediatric brain tumors. To provide safe and effective health services, quantifying and evaluating quality of care are important. To do this, there is a need for universal measures in the form of indicators reflecting quality of the delivered care. The objective of this study was to analyze currently applied quality indicators in pediatric brain tumor surgery and identify factors associated with poor outcome at a tertiary neurosurgical referral center in western Norway.

METHODS

All patients younger than 18 years of age who underwent surgery for an intracranial tumor at the Department of Neurosurgery at Haukeland University Hospital in Bergen, Norway, between 2009 and 2020 were included. The primary outcomes of interest were classic quality indicators: 30-day readmission, 30-day reoperation, 30-day mortality, 30-day nosocomial infection, and 30-day surgical site infection (SSI) rates; and length of stay. The secondary aim was the identification of risk factors related to unfavorable outcome. The authors also conducted a systematic literature review. Articles concerning pediatric brain tumor surgery reporting at least two quality indicators were of interest.

RESULTS

The authors included 82 patients aged 0-17 years. The 30-day outcomes for unplanned reoperation, unplanned remission, mortality, nosocomial infection, and SSI were 9.8%, 14.6%, 0%, 6.1%, and 3.7%, respectively. Unplanned reoperation was associated with eloquent localization (p = 0.009), primary emergency surgery (p = 0.003), and CSF diversion procedures (p = 0.002). Greater tumor volume was associated with unplanned readmission (p = 0.008), nosocomial infection (p = 0.004), and CSF leakage (p = 0.005). In the systematic review, after full-text screening, 16 articles were included and provided outcome data for 1856 procedures. Overall, the 30-day mortality rate was low, varying from 0% to 9.3%. The 30-day reoperation rate varied from 1.5% to 12%. The SSI rate ranged between 0% and 3.9%, and 0% to 17.4% of patients developed CSF leakage. Four studies reported infratentorial tumor location as a risk factor for postoperative CSF leakage.

CONCLUSIONS

The 30-day outcomes in the authors' department were comparable to published outcomes. The most relevant factors related to unfavorable outcomes are tumor volume and location, both of which are not modifiable by the surgeon. This highlights the importance of risk adjustment. This evaluation of quality indicators reveals concerns related to the unclear and nonstandardized definitions of outcomes. Standardized outcome definitions and documentation in a large and multicentric database are needed in the future for further evaluation of quality indicators.

Long-term outcome after management of pilocytic astrocytoma in the posterior fossa in a pediatric population

Background and purpose

To assess the impact of posterior fossa pilocytic astrocytoma (PA) removal in pediatric patients, with special focus on postoperative neurological outcome after repeated surgery for tumor remnants.

Methods

Our institutional database was screened for patients with PA treated between 2000 and 2019. Patients ≤ 18 years of age with complete clinical records, preoperative contrast enhanced magnetic resonance imaging (MRI) and postoperative follow-up time of ≥ 6 months were suitable for study inclusion. Functional outcome was quantified with the modified Ranking Scale (mRS) score and assessed at admission, at discharge and at every follow-up investigation. Predictors of hydrocephalus, cranial nerve deficits and tumor recurrence were evaluated.

Results

A total of 57 pediatric patients with a mean age of 7.7 ± 4.8 years were included in the analysis. 27 (47.3%) children suffered from hydrocephalus at diagnosis, out of which 19 (33.3%) required a subsequent VP-Shunt. 22 (39.3%) patients had a partial resection, of which 9 (40.9%) went through second-look surgery. 2 patients with initially radiological confirmation of complete resection, had a tumor recurrence at FU and needed second-look surgery. Among the children requiring second-look surgery, 7 (63.6%) had a complete resection. Favorable outcome (mRS≤2) after initial and second-look surgery was observed in 52 patients (91.2%). Univariate analysis identified tumor location in the floor of the 4th ventricle (p = 0.030), and repeated surgery for tumor remnant removal (p = 0.043) as predictors for post-operative cranial nerve deficits. Multivariate analysis confirmed this independent association. The incidence of tumor recurrence occurred more often in patients with previous partial resection (p = 0.009) as well as in lesions located in the cerebellar peduncles (p = 0.043). Partial resection remained an independent predictor after multivariate logistic regression analysis (p = 0.045).

Conclusions

Incomplete resection of posterior fossa PA is a risk factor for tumor recurrence and repeated surgery to remove tumor remnants increases the risk of new postoperative deficits. Thus, the risk of iatrogenic deterioration due to second look surgery should be implemented in the primary pre- and intraoperative decision-making.

Concise review of radiosurgery for contemporary management of pilocytic astrocytomas in children and adults

Pilocytic astrocytoma (PA) may be seen in both adults and children as a distinct histologic and biologic subset of low-grade glioma. Surgery is the principal treatment for the management of PAs; however, selected patients may benefit from irradiation particularly in the setting of inoperability, incomplete resection, or recurrent disease. While conventionally fractionated radiation therapy has been traditionally utilized for radiotherapeutic management, stereotactic irradiation strategies have been introduced more recently to improve the toxicity profile of radiation delivery without compromising tumor control. PAs may be suitable for radiosurgical management due to their typical appearance as well circumscribed lesions. Focused and precise targeting of these well-defined lesions under stereotactic immobilization and image guidance may offer great potential for achieving an improved therapeutic ratio by virtue of radiosurgical techniques. Given the high conformality along with steep dose gradients around the target volume allowing for reduced normal tissue exposure, radiosurgery may be considered a viable modality of radiotherapeutic management. Another advantage of radiosurgery may be the completion of therapy in a usually shorter overall treatment time, which may be particularly well suited for children with requirement of anesthesia during irradiation. Several studies have addressed the utility of radiosurgery particularly as an adjuvant or salvage treatment modality for PA. Nevertheless, despite the growing body of evidence supporting the use of radiosurgery, there is need for a high level of evidence to dictate treatment decisions and establish its optimal role in the management of PA. Herein, we provide a concise review of radiosurgery for PA in light of the literature.

Outcome of Childhood Cerebellar Pilocytic Astrocytoma: A Series With 20 Years of Follow Up

Background: Cerebellar pilocytic astrocytoma (PCA) is one of the few CNS tumors that can be cured with gross-total removal (GTR). In this series, we had 39 patients diagnosed with cerebellar PCA, 27 patients (70%) had GTR, and mean follow-up period was 62 months with no tumor recurrence.

Objective: To assess the long-term outcome of childhood cerebellar PCA treated at our institute during the period 2000-2020 and to highlight our surgical protocol.

Methodology: Retrospective review of all patients under 18 years of age who were diagnosed with cerebellar PCA and had surgical excision between 2000 and 2020 at the Medical City of King Saud University.

Results: The study included 39 patients: 17 males and 22 females, the mean age was 8.4 years. Radiologically, the tumor was solid in eight patients, cystic in 15 patients, and mixed components were found in 16 patients. The lesion was located in the right cerebellar hemisphere in 12 patients, left cerebellar hemisphere in five patients, and midline 22 patients. The tumor size ranged from 2 to 7 cm in its greatest diameter, it was <5 cm in 13 patients and >5 cm in 26 patients. Thirty-one patients had preoperative hydrocephalus. GTR of the tumor was achieved in 27 patients and subtotal resection (STR) was done in 12 patients, 18 patients required permanent ventriculoperitoneal (V-P) shunt, and five patients had postoperative radiotherapy. Postoperative complications included infection in two patients, cerebellar mutism in two patients, and significant neurologic disability in four patients. The duration of follow-up ranged from 0 to 240 months (mean follow-up period: 62.0 months). The outcome at 10 years was good in 30 patients, fair in four patients, poor in four patients, and one patient died. Recurrence was documented in nine patients, seven of them had GTR and two had STR.

Conclusion: GTR, if achievable, is curative for childhood cerebellar PCA. Many posterior fossa surgical complications could be avoided with watertight dural closure. Although new dural substitutes are available we prefer using autologous grafts (pericranium). It is easy to harvest pericranial graft from the external ventricular drain (EVD) site. The insertion of EVD synchronously with GTR of the tumor and gradual weaning of EVD could avoid the insertion of V-P shunt.

Effect of radiation therapy on overall survival following subtotal resection of adult pilocytic astrocytoma

OBJECTIVE

Pilocytic astrocytoma (PCA) is a low-grade glioma that primarily presents in children, but can also present in adulthood. Ideal primary treatment for PCA is gross total resection. However, for patients who are only able to undergo subtotal resection, the optimal course of post-operative therapy remains unclear. We investigated the association of patient characteristics and radiation therapy (RT) with overall survival specifically for adult PCA patients who underwent subtotal tumor resection.

METHODS

Information on adult patients (age ≥18 years old) who underwent subtotal PCA resection between 2004 and 2016 was collected from the National Cancer Database (NCDB). A multivariate Cox proportional hazards model was utilized to determine factors associated with overall survival.

RESULTS

A total of 451 patients were identified. The mean age of our patient cohort was 36.8 years old, and the majority of patients (83.4%) did not receive RT following subtotal PCA resection. Overall median survival was >93.8 months. On multivariate analysis, patients who were older at diagnosis (hazard ratio [HR] = 1.04, 95% confidence interval [CI] = 1.02-1.06, p < 0.01), black (HR = 2.35, CI = 1.05-5.23, p = 0.037), had a Charlson/Deyo comorbidity score ≥ 1 (HR = 2.27, CI = 1.00-5.14, p = 0.049), or received RT during their initial treatment (HR = 3.77, CI = 1.77-8.03, p < 0.01) had a significantly higher risk of death following subtotal PCA resection.

CONCLUSION

Post-operative RT was associated with a significantly higher risk of death among adults who underwent subtotal PCA resection. Our findings provide support for further inquiry into the efficacy of RT within this patient population.

Survival and Prognosis of Patients with Pilocytic Astrocytoma: A Single-Center Study

Background

Pilocytic astrocytoma (PA) is a brain tumor that is relatively more common in children and young adults.

Methods

We retrospectively reviewed the medical records of patients with PA treated at a single center between 1988 and 2018.

Results

We included 31 subjects with PA. The median age at diagnosis was 13.4 years, and the median follow-up duration was 9.9 years. The total PA group had a 10-year disease-specific survival (DSS) rate of 92.6% [95% confidence interval (CI), 82.6–100] and 10-year progression-free survival (PFS) rate of 52.8% (95% CI, 32.0–73.6). In patients aged <20 years, tumors were more likely to be located in sites in which gross total tumor resection (GTR) was impossible. No statistically significant difference in 10-year DSS was found between the GTR (100%) and non-GTR (89.7%; 95% CI, 76.2–100; p=0.374) groups. However, a statistically significant difference in 10-year PFS was found between the GTR (100%) and non-GTR groups (30.7%; 95% CI, 8.6–52.8; p=0.012). In the non-GTR group, no statistically significant difference in 10-year DSS was found between the patients who received immediate additional chemotherapy and/or radiotherapy (Add-Tx group, 92.9%; 95% CI, 79.4–100) and the non-Add-Tx group (83.3%; 95% CI, 53.5–100; p=0.577). No statistically significant difference in 10-year PFS was found between the Add-Tx group (28.9%; 95% CI, 1.7–56.1) and non-Add-Tx group (33.3%; 95% CI, 0–70.9; p=0.706).

Conclusion

The PFS of the patients with PA in our study depended only on the degree of surgical excision associated with tumor location. This study is limited by its small number of patients and retrospective nature. A multicenter and prospective study is necessary to confirm these findings.

Predictive measures and outcomes of extent of resection in juvenile pilocytic astrocytoma

PURPOSE

The present study aims to determine the tumor-related, clinical, and demographic factors associated with extent of resection (EOR) and post-operative outcomes in JPA patients.

METHODS

All patients with JPA, identified from a single-center brain tumour data base, were included in this retrospective analysis. Pre-operative MRI scans were reviewed by a single neurosurgeon blinded to the EOR. JPA cases that exhibited no residual tumor post-operatively were assigned to the GTR group, all other tumors were assigned to the <GTR group. Tumor-related, clinical and demographic variables as well as perioperative morbidities were compared between both groups.

RESULTS

Of the 28 patients included, 15 had a GTR (46% male; median age: 7.5 years; range: 1.16-14.9) and 13 had <GTR (69.2% male; median age: 10.6 years; range: 0.66-17.68). Tumor location reached statistical significance, as there were significantly more cerebellar tumors in the GTR group (86.7%) compared to the <GTR group (38.5%) (p = 0.016). GTR cases had a significantly longer average follow-up interval (6.6 months) than <GTR cases (4.5 months) (p = 0.031). All demographic variables, clinical variables and tumor-related factors showed no significant differences between the two groups. There were no differences between GTR and <GTR cases in terms of perioperative outcomes.

CONCLUSIONS

This study shows other than location of the lesion in the cerebellum, demographic, clinical and tumor-related variables are not associated with EOR in children with JPA. GTR was associated with an extended follow-up interval but not with increased perioperative morbidities compared to those with <GTR.

Characteristics, survival and incidence rates and trends of pilocytic astrocytoma in children in the United States; SEER-based analysis

INTRODUCTION

Pilocytic astrocytoma (PA) is a neurological neoplasm and a common neurological tumor among children. No recent reports have studied the recent demographic characteristics of PA cases in the US.

METHODOLOGY

We used the Surveillance, Epidemiology, and End Results (SEER) Program to retrieve data on children diagnosed with PA between 2000 and 2015. We calculated the incidence, annual percentage changes (APC), and survival.

RESULTS

Our study included 3084 children with PA, with an incidence of 8.227 per 1,000,000 person-years, being highest among whites (9.062), and children aged 1-4 year (11.175). Overall incidence in children increased significantly over the study period, with an APC of 0.825% (95% CI[0.027-1.630], P = .044). Moreover, incidence among blacks increased significantly over the study period (APC = 3.466%, 95% CI[0.342-6.688], P = .032), but did not change among other races. The relative 5-year survival of included patients was 95.3%, with patients younger than 1 year having the worst survival.

CONCLUSIONS

Overall PA incidence and incidence among blacks has been increasing last decade. Additionally, PA survival was found to be worse among infants. Further studies are also needed to investigate the effect of the age and race on the incidence and survival of PA.

Evidence-Based Practice: Temozolomide Beyond Glioblastoma

PURPOSE OF REVIEW

Temozolomide is a first-line treatment for newly diagnosed glioblastoma. In this review, we will examine the use of temozolomide in other contexts for treating gliomas, including recurrent glioblastoma, glioblastoma in the elderly, diffuse low- and high-grade gliomas, non-diffuse gliomas, diffuse intrinsic pontine glioma (DIPG), ependymoma, pilocytic astrocytoma, and pleomorphic xanthoastrocytoma.

RECENT FINDINGS

Temozolomide improved survival in older patients with glioblastoma, anaplastic gliomas regardless of 1p/19q deletion status, and progressive ependymomas. Temozolomide afforded less toxicity and comparable efficacy to radiation in high-risk low-grade gliomas and to platinum-based chemotherapy in pediatric high-grade gliomas. The success of temozolomide in promoting survival has expanded beyond glioblastoma to benefit patients with non-glioblastoma tumors. Identifying practical biomarkers for predicting temozolomide susceptibility, and establishing complementary agents for chemosensitizing tumors to temozolomide, will be key next steps for future success.

Novel Surgical and Radiologic Risk Factors for Progression or Recurrence of Pediatric Pilocytic Astrocytoma

INTRODUCTION

Pilocytic astrocytomas (PA) are a common, benign childhood tumor known for their slow growth rates and excellent prognosis. The aim of our study was to characterize patient, tumor, and imaging-related risk factors for recurrence and progression of disease.

METHODS

We identified 116 patients with PA who underwent surgery at our institution between 2000 and 2015. Data were collected retrospectively from the clinical charts.

RESULTS

The mean age at resection was 7 ± 5 years (range 0.5-31) and mean follow-up was 6 ± 3 years. Initial resection was complete in 33 patients (29%), subtotal in 78 patients (67%), and biopsy in 5 patients (4%). A total of 45/116 (40%) patients experienced either recurrence or progression after initial resection with a mean time to recurrence or progression of 2.2 years. Bivariate analysis identified subtotal resection, tumor location, age at diagnosis, and imaging features (i.e., T2 invasion, exophytic component, hemorrhage, and solid tumors) as factors significantly associated with recurrence or progression (p < 0.05). Conversely, PAs that were completely resected, predominately cystic, and located in the cerebellum were significantly associated with no recurrence or progression (p < 0.05). Multivariate regression analysis narrowed down 4 robust risk factors: extent of resection, T2 invasion, predominantly solid lesions, and presence of an exophytic component (p < 0.05).

CONCLUSION

Total surgical removal of PA has been the most important prognostic factor for the clinical course of PA. Our study reveals additional risk factors for the recurrence or progression of disease: tumor invasion, solid composition, and tumors with an exophytic component.

Cognitive features and surgical outcome of patients with long-term epilepsy-associated tumors (LEATs) within the temporal lobe

OBJECTIVE

The objective of the study was to evaluate cognitive and epilepsy-related features in 166 surgically treated patients with epilepsy with long-term epilepsy-associated tumors (LEATs) located in the temporal lobe.

METHOD

Pre- and postsurgical cognitive as well as the one-year seizure outcome of adult patients with histopathologically confirmed LEATs (28 grade-I dysembryoplastic neuroepithelial tumors (DNET), 95 grade-I gangliogliomas (GG), 24 grade-I pilocytic astrocytomas (PA), 9 grade-II pleomorphic xanthoastrocytoma (PXA), 10 grade-II diffuse astrocytoma (DA)) who underwent epilepsy surgery in Bonn/Germany between 1988 and 2012 were evaluated.

RESULTS

At baseline, tumor groups differed in regard to age at epilepsy onset and location within the temporal lobe. Postoperative seizure freedom was achieved most frequently (>77.8%) in DNET, GG, and DA, less often in PXA (62.5%) and the least in PA (56.5%). Preoperative memory was impaired in 67.1% of all patients, executive functions in 44.7%, and language in 45.5%. Patients with PA displayed the poorest cognitive performance. Individual significant memory decline that was observed in 27.1% of all patients was predicted by left-sided surgery, a mesial pathology, and extended hippocampal resection. Executive functions depended on antiepileptic drug (AED) load and remained stable (72.0%) or even improved (21.6%) after surgery. Language functions were unchanged in 89.5% of patients.

CONCLUSION

Patients with LEATs in the temporal lobe frequently show cognitive impairments. Predictors for pre- and postoperative cognition mostly correspond to what is known for temporal lobe epilepsy and resections in general. However, different tumor types appear to be associated with different cognitive and seizure outcomes with astrocytoma as the least benefitted group.

Application of fluorescein sodium in the resection of vermis pilocytic astrocytomas

Background

Pilocytic astrocytomas (PAs) are slow growing neoplasms and usually located at the cerebellum. There has been certainty regarding the truthful benefit of surgical resection for patients with PA. Gross total resection (GTR) of PAs, especially those being situated in deep regions, remains a surgical challenge. Generally, they are considered as benign and usually develop in young patients. PAs, belonging to WHO I can be cured by radical resection. The patients with PA have excellent prognosis if complete resection can be conducted. The use of fluorescein in vermis PA surgery has not been yet reported. Our data presents fluorescein facilitates surgical resection of vermis PA.

Methods

Five milligrams per kilogram of fluorescein sodium was intravenously injected directly before general anesthesia for the three patients with PA. The yellow 560 filter was employed for microsurgical tumor resection. Surgical outcomes were assessed concerning the extent of resection.

Results

Most portion of PA in the three cases was found to be highly fluorescent after intravenous fluorescein sodium injection, which markedly enhanced tumor visibility. Gross total resection in all of the patients was achieved without further neurological deficits. No adverse effects and complications resulting from fluorescein sodium were observed over the postoperative course.

Conclusions

Intraoperative guidance by fluorescein sodium as a new, simple, safe, and practical procedure can enhance the fidelity of tumor tissue and increase the possibility of completely resecting PAs.

Neurosurgical tools to extend tumor resection in pediatric hemispheric low-grade gliomas: iMRI

INTRODUCTION

The treatment of low-grade gliomas (LGGs) in pediatric age is still controversial. However, most authors report longer life expectancy in case of completely removed cerebral gliomas. Intraoperative magnetic resonance imaging (iMRI) is increasingly utilized in the surgical management of intra-axial tumor in adults following the demonstration of its effectiveness. In this article, we analyze the management of LGG using iMRI focusing on its impact on resection rate and its limits in the pediatric population.

METHODS

We performed review of the literature regarding the treatment of LGG using iMRI focusing on its impact on resection rate and its limits in the pediatric population. Some exemplary cases are also described.

RESULTS

Intraoperative MRI allowed extension of tumor resection after the depiction of residual tumor at the intraoperative imaging control from 21 to 52 % of the cases in the published series. Moreover, the early reoperation rate was significantly lower when compared with the population treated without this tool (0 % vs 7-14 %). Some technical difficulties have been described in literature regarding the use of iMRI in the pediatric population especially for positioning due to the structure of the headrest coil designed for adult patients.

CONCLUSION

The analysis of the literature and our own experience with iMRI in children indicates significant advantages in the resection of LGG offered by the technique. All these advantages are obtained without elongation of the surgical times or increased risk for complications, namely infection. The main limit for a wider diffusion of iMRI for the pediatric neurosurgical center is the cost required, for acquisition of the system, especially for high-field magnet, and the environmental and organizational changes necessary for its use.

A new NFIA:RAF1 fusion activating the MAPK pathway in pilocytic astrocytoma

Pilocytic astrocytoma (PA) is one of the most common brain cancers among children and activation of the Mitogen-Activated Protein Kinase (MAPK) pathway is considered the hallmark. In the majority of cases, oncogenic BRAF fusions or BRAF V600E mutations are observed, while RAF1 or NF1 alterations are more rarely found. However, in some cases, no apparent cancer driver events can be identified. Here, we describe a novel fusion between the transcription factor nuclear factor 1A (NFIA) and Raf-1 proto-oncogene (RAF1) in a 5-year old boy with PA. The novel fusion was identified as part of a comprehensive genomic tumor profiling. We show that the NFIA:RAF1 fusion results in constitutive Raf1 kinase activity, leading to activation of downstream MEK1/2 cascade and increased proliferation of cancer cells. The NFIA:RAF1 fusion displayed distinct subcellular localization towards the plasma membrane indicative of Raf-1 activation, in contrast to both wild type NFIA and Raf-1, which were localized in the nucleus and cytoplasm, respectively. In conclusion, our data support the existence of rare oncogenic RAF1 fusions with constitutive Raf-1 activity. This highlights the need for broad genetic testing in order to refine diagnostics of PA and to unravel potential treatment options, e.g. with MEK inhibitors.

Model-Based Evaluation of Spontaneous Tumor Regression in Pilocytic Astrocytoma

Pilocytic astrocytoma (PA) is the most common brain tumor in children. This tumor is usually benign and has a good prognosis. Total resection is the treatment of choice and will cure the majority of patients. However, often only partial resection is possible due to the location of the tumor. In that case, spontaneous regression, regrowth, or progression to a more aggressive form have been observed. The dependency between the residual tumor size and spontaneous regression is not understood yet. Therefore, the prognosis is largely unpredictable and there is controversy regarding the management of patients for whom complete resection cannot be achieved. Strategies span from pure observation (wait and see) to combinations of surgery, adjuvant chemotherapy, and radiotherapy. Here, we introduce a mathematical model to investigate the growth and progression behavior of PA. In particular, we propose a Markov chain model incorporating cell proliferation and death as well as mutations. Our model analysis shows that the tumor behavior after partial resection is essentially determined by a risk coefficient γ, which can be deduced from epidemiological data about PA. Our results quantitatively predict the regression probability of a partially resected benign PA given the residual tumor size and lead to the hypothesis that this dependency is linear, implying that removing any amount of tumor mass will improve prognosis. This finding stands in contrast to diffuse malignant glioma where an extent of resection threshold has been experimentally shown, below which no benefit for survival is expected. These results have important implications for future therapeutic studies in PA that should include residual tumor volume as a prognostic factor.

Differences in the clinical courses of pediatric and adult pilocytic astrocytomas with progression: a single-institution study

PURPOSE

Pilocytic astrocytoma (PA) is a World Health Organization grade I neoplasm that generally follows a benign course. However, in some patients, PA exhibits an aggressive clinical course. Here, we examined the clinical course of pediatric and adult PAs with progression at a single institution.

METHODS

Between 1995 and 2013, 39 patients with PA were treated. Nineteen were pediatric patients (mean age, 12 years; range, 1-17 years) with a male-to-female patient ratio of 10:9, while 20 were adults (mean age, 36.4 years; range, 19-65 years) with a male-to-female ratio of 9:11. We analyzed and compared tumor location, extent of tumor resection, adjuvant treatment, and clinical course in all patients.

RESULTS

In the 19 pediatric patients, tumors were located in the cerebellar vermis, cerebellar hemisphere, optic pathways plus hypothalamus, hypothalamus, brainstem, and the temporal lobe in 6 (31.6%), 5 (26.3%), 3 (15.8%), 2 (10.5%), and 2 (10.5%) patients and 1 (5.3%) patient, respectively. The mass was totally, subtotally, or partially resected in 11 (57.9%), 2 (10.5%), and 4 (21.1%) patients, respectively; biopsies were performed in 2 (10.5%) patients. Immediate postoperative adjuvant treatment was carried out in 6 patients. Tumor progression was detected in 3 patients at 3.0, 4.6, and 5.2 years after treatment, respectively, without significant symptoms. In the 20 adult patients, tumors were located in the cerebellar hemisphere, cerebellar vermis, hypothalamus, brainstem, cerebral hemisphere, and lateral ventricle in 5 (25%), 4 (20%), 3 (15%), 3 (15%), 3 (15%), and 2 (10%) patients, respectively. The mass was totally, subtotally, or partially resected in 11 (55%) and 6 (30%) patients and 1 (5%) patient, respectively; biopsies were performed in 2 patients. Immediate adjuvant treatment was carried out in 2 patients. Progression was detected in 3 patients at 0.3, 0.9, and 2.5 years after treatment, respectively, with progressive neurologic symptoms. There was one case of disease-related mortality during follow-up among the adult patients.

CONCLUSION

Most of the PA cases evaluated in this study were benign. However, tumor progression in adult PAs followed a more aggressive clinical course than those in pediatric PAs.

Current Understanding of BRAF Alterations in Diagnosis, Prognosis, and Therapeutic Targeting in Pediatric Low-Grade Gliomas

The mitogen-activated protein kinase (MAPK) pathway is known to play a key role in the initiation and maintenance of many tumors as well as normal development. This often occurs through mutation of the genes encoding RAS and RAF proteins which are involved in signal transduction in this pathway. BRAF is one of three RAF kinases which act as downstream effectors of growth factor signaling leading to cell cycle progression, proliferation, and survival. Initially reported as a point mutation (V600E) in the majority of metastatic melanomas, other alterations in the BRAF gene have now been reported in a variety of human cancers including papillary thyroid cancer, colon carcinomas, hairy cell leukemia, and more recently in gliomas. The identification of oncogenic mutations in the BRAF gene have led to a revolution in the treatment of metastatic melanoma using targeted molecular therapies that affect the MAPK pathway either directly through BRAF inhibition or downstream through inhibition of MEK. This review describes the molecular biology of BRAF in the context of pediatric low-grade gliomas, the role of BRAF as a diagnostic marker, the prognostic implications of BRAF, and evidence for therapeutic targeting of BRAF.

Postoperative Surveillance Magnetic Resonance Imaging for Cerebellar Astrocytoma

Introduction:

Patients with low grade astrocytomas generally have good prognosis when total resection can be achieved, but surveillance neuroimaging is commonly performed to detect recurrence or progression. This study evaluated the utility and yield of such strategy for pilocytic and non-pilocytic cerebellar astrocytomas.

Methods:

A 20-year retrospective review was performed of patients undergoing resection of cerebellar astrocytoma at a single institution. A negative MRI string (NMS) ratio was computed as the fraction of total follow-up period over which surveillance neuroimaging was negative for recurrence or progression. Chi-squared analysis differentiated NMS ratio by resection extent and lesion histopathology.

Results:

Twenty-eight patients with pilocytic (n=15) and non-pilocytic (n=13) astrocytoma underwent 34 craniotomies, with total resection in 19 cases. Surveillance MRIs (n=167) among total resection patients were uniformly negative for recurrent disease at average seven years follow-up (NMS ratio = 1.0). The 43 surveillance MRIs among subtotal resection patients revealed disease progression in two patients within six months of operation (NMS ratio = 0.78, p<0.05). No differences in NMS ratio were observed between pilocytic and non-pilocytic astrocytoma subtypes.

Discussion:

This study illustrates pediatric patients with low-grade cerebellar astrocytomas undergoing total resection may not benefit from routine surveillance neuroimaging, primarily because of low recurrence likelihood. Patients with subtotal resection may benefit from surveillance of residual disease, with further work aimed at exploring the schedule of such follow-up.

Suprasellar pilocytic astrocytoma: one national centre's experience

INTRODUCTION

Pilocytic astrocytomas in the supratentorial compartment make up 20 % of all brain tumours in children with only 5 % of these arising in the suprasellar region. Optic pathway gliomas or suprasellar gliomas are often seen in neurofibromatosis type 1 (NF1) patients. Given their location, suprasellar pilocytic astrocytomas are challenging to manage surgically with high morbidity rates from surgical resection. We assess our cohort of patients with suprasellar pilocytic astrocytoma and document our experience.

METHOD

A retrospective review of patients diagnosed with suprasellar glioma between 2000-October 2012. We included patients diagnosed with optic pathway glioma based on radiological features (with or without biopsy) and those who had a biopsy confirming pilocytic astrocytoma.

RESULTS

Fifty-three patients included (sporadic tumours 24 and NF1 related 29). Fifteen sporadic and four NF1 patients were biopsied. Twelve sporadic and 13 NF1 patients were initially treated with chemotherapy while only 1 patient had radiotherapy initially. Progression was noted in 58 % of the sporadic group and 24 % of the NF1 group. The only significant factor for progression was NF1 status (p = 0.026).

CONCLUSION

Management should be guided by individual patient circumstance. In our cohort, chemotherapy did not significantly improve progression free survival; however, NF1 status significantly correlated with the decreased progression.

Pilocytic astrocytomas of the optic nerve and their relation to pilocytic astrocytomas elsewhere in the central nervous system

Pilocytic astrocytoma is a low-grade glioma that affects mostly children and young adults and can occur anywhere in the central nervous system. Pilocytic astrocytoma of the optic nerve is an equally indolent subtype that is occasionally associated with neurofibromatosis type 1. In earlier studies, this subtype was considered within the larger category of 'optic pathway glioma,' which included infiltrating astrocytomas and other hypothalamic tumors. However, there have been suggestions that gliomas in the optic nerve, and especially pilocytic astrocytoma of the optic nerve, are biologically different from tumors within the hypothalamus and other parts of the optic tract. Furthermore, the recent discovery of BRAF duplication and fusion with the KIAA1549 gene is reported to be more typical for posterior fossa tumors, and the rate of this aberration is not well known in pilocytic astrocytoma of the optic nerve. To determine the distinction of pilocytic astrocytoma of the optic nerve from pilocytic astrocytoma of the posterior fossa and to investigate the prevalence of BRAF aberrations, we reviewed the clinicopathological and molecular features of all such patients in our institution. Our study demonstrates that BRAF duplication is more frequent in posterior fossa tumors compared with pilocytic astrocytoma of the optic nerve (P=0.011). However, the rates of phospho-MAPK1 and CDKN2A expression were high in both pilocytic astrocytoma of the optic nerve and posterior fossa pilocytic astrocytoma, suggesting that the MAPK pathway is active in these tumors. Our study supports the notion that BRAF duplication is more typical of posterior fossa pilocytic astrocytoma and that molecular alterations other than KIAA1549 fusion may underlie MAPK pathway activation in pilocytic astrocytoma of the optic nerve.

Gliomas of the posterior fossa in adults

Infratentorial gliomas are relatively rare tumors compared to their supratentorial counterparts. As such they have not been extensively characterized as a group and are usually excluded from clinical studies. Using our database we aimed to characterize adult gliomas involving the posterior fossa with respect to their clinical behavior and prognostic factors. We reviewed our neurosurgical and neuro-oncological data bases for adult patients diagnosed with gliomas involving the posterior fossa between 1996 and 2010. Of 1,283 glioma patients, 57 patients with gliomas involving the posterior fossa were identified (4.4 %). Tumors were further classified by location as primary brainstem (n = 21) and primary cerebellar (n = 18) tumors. On univariate analysis survival was correlated to tumor grade and KPS. In addition we have identified a unique group of patients (n = 18) with previously diagnosed supratentorial gliomas who subsequently developed noncontiguous secondary infratentorial extension of their tumors with subsequent rapid clinical deterioration. Gliomas of the posterior fossa comprise a heterogeneous group of tumors. Histological grade of the tumor was found to be the main prognostic factor. Survival of primary cerebellar gliomas is comparable to supra-tentorial gliomas, while brainstem gliomas in adults fare better than in the pediatric population. Secondary extension of supratentorial gliomas to the posterior fossa signifies a grave prognosis.

Neurological morbidity of surgical resection of pediatric cerebellar astrocytomas

BACKGROUND

Review of children with low-grade cerebellar astrocytoma (LGCA) prior to 1992 showed a 98% rate of gross total resection (GTR) but a concerning incidence of permanent neurological dysfunction. The purpose of this study was to determine the rate of GTR of LGCA since 1992 and frequency of neurologic injury.

METHODS

Retrospective review of children with LGCA was performed. CT/MR scans were rereviewed to assess extent of resection. Primary outcomes included incidence of GTR and incidence of permanent new neurological deficits. Other outcomes included late effects severity score (LESS), Bloom score for functional status, and educational assessment.

RESULTS

Of 50 LGCA, GTR was achieved in 38 (76%) compared to 43 of 44 (98%) prior to 1992 (p < 0.004). Permanent new neurologic deficits from surgery occurred in 16% compared to 18% in the prior era (p = 0.61). For 35 patients operated on by the 2 surgeons in the prior study, 74% had GTR, with permanent neurological deficits in 8.6%. At latest follow-up, all patients were alive, 16% with residual tumor. LESS was two or less (mild or no deficit) in 94%. Bloom score was one or two (no or mild disability) in 90%. Eighty-six percent attended normal school.

CONCLUSIONS

Less aggressive resection of LGCA in children may reduce postoperative neurologic deficits in the hands of the same surgeons as in the prior study but not overall at our institution. The good long-term outcomes suggest that it may be appropriate to do incomplete resection rather than risk additional neurological deficit.

Differential expression and methylation of brain developmental genes define location-specific subsets of pilocytic astrocytoma

Pilocytic astrocytomas (PAs) are the most common brain tumors in pediatric patients and can cause significant morbidity, including chronic neurological deficiencies. They are characterized by activating alterations in the mitogen-activated protein kinase pathway, but little else is known about their development. To map the global DNA methylation profiles of these tumors, we analyzed 62 PAs and 7 normal cerebellum samples using Illumina 450K microarrays. These data revealed two subgroups of PA that separate according to tumor location (infratentorial versus supratentorial), and identified key neural developmental genes that are differentially methylated between the two groups, including NR2E1 and EN2. Integration with transcriptome microarray data highlighted significant expression differences, which were unexpectedly associated with a strong positive correlation between methylation and expression. Differentially methylated probes were often identified within the gene body and/or regions up- or downstream of the gene, rather than at the transcription start site. We also identified a large number of differentially methylated genes between cerebellar PAs and normal cerebellum, which were again enriched for developmental genes. In addition, we found a significant association between differentially methylated genes and SUZ12 binding sites, indicating potential disruption of the polycomb repressor complex 2 (PRC2). Taken together, these data suggest that PA from different locations in the brain may arise from region-specific cells of origin, and highlight the potential disruption of key developmental regulators during tumorigenesis. These findings have implications for future basic research and clinical trials, as therapeutic targets and drug sensitivity may differ according to tumor location.

Arrested growth and spontaneous tumor regression of partially resected low-grade cerebellar astrocytomas in children

PURPOSE

The prognosis of children with low-grade cerebellar astrocytoma who have partial resection of tumor is largely unpredictable. The purpose of this study was to review the long-term outcome of such patients.

METHODS

The medical charts, imaging findings, operative notes, histopathological reports, and survival times of 12 patients with cerebellar astrocytoma were reviewed.

RESULTS

Five patients had total resection and seven had partial resection. Nine patients had grade I histology and three patients had grade II. Follow-up duration ranged from 3 to 25 years. Among the seven patients with residual tumor, five had tumor progression, one had arrested tumor growth, and one had spontaneous tumor regression. Five patients with partial resection received radiotherapy and three had malignant transformation of tumor during follow-up. Six patients, including five who had partial resection, underwent a second operation. One patient with partial resection died of pneumonia 23 years after surgery.

CONCLUSIONS

Patients with complete tumor resection had a better prognosis than patients with partial resection. For patients with partial resection, we recommend a "wait and see" policy with surveillance using MRI. The phenomenon of arrested tumor growth and spontaneous tumor regression in patients with cerebellar astrocytoma who have subtotal resection warrants further study.

Long-term follow-up of the multicenter, multidisciplinary treatment study HIT-LGG-1996 for low-grade glioma in children and adolescents of the German Speaking Society of Pediatric Oncology and Hematology

The Hirntumorstudien (HIT)-LGG-1996 protocol offered a comprehensive treatment strategy for pediatric patients with low-grade glioma (LGG), ie, observation, surgery, adjuvant radiotherapy, and chemotherapy to defer the start of irradiation in young children. In this current study, we sought to determine clinical factors for progression and survival. Between October 1, 1996 and March 31, 2004, 1031 patients were prospectively recruited into an observation arm (n = 668) and a nonsurgical arm stratifying 12 months of vincristine-carboplatin chemotherapy (n = 216) and conventional radiotherapy/brachytherapy (n = 147) in an age-dependent manner. Median patient age was 6.9 years; 28 patients had diencephalic syndrome, 44 had dissemination, and 108 had neurofibromatosis type 1(NF-1). Main tumor location was the supratentorial midline (40.4%), and the main histology was pilocytic astrocytoma (67.9%). Following a median observation of 9.3 years, 10-year overall survival (OS) was 0.94 and 10-year event-free survival (EFS) was 0.47. Ten-year progression-free survival was 0.62 following radiotherapy and 0.44 following chemotherapy. Sixty-one of 216 chemotherapy patients received radiotherapy 0.3-8.7 years after initial diagnosis. By multivariate analysis, diencephalic syndrome and incomplete resection were found to be unfavorable factors for OS and EFS, age ≥11 years for OS, and supratentorial midline location for EFS. Dissemination, age <1 year, and nonpilocytic histology were unfavorable factors for progression following radiotherapy (138 patients); and diencephalic syndrome, dissemination, and age ≥11 years were unfavorable factors following chemotherapy (210 patients). NF-1 patients and boys experienced prolonged tumor stabilization with chemotherapy. A nationwide multimodal treatment strategy is feasible for pediatric LGG. Extended follow-up yielded results comparable to single-institution series for the treatment groups. Three-quarters of surviving chemotherapy patients have not yet received radiation therapy. Infants with or without diencephalic syndrome and dissemination bear the highest risk for death and progression following diagnosis or treatment.

Biologic tumor behavior in pilocytic astrocytomas

PURPOSE

The aim is to describe the behavior of pilocytic astrocytoma (PAs) and its effects on patient prognosis by using flow cytometric, immunohistochemical and cytogenetic methods. We also aim to find out whether there is any difference between differently localized tumors by the above mentioned analyses.

METHODS

We studied DNA index, expression of p53, p16, pRb, MMAC/PTEN1, VEGF, MIB-1 index and chromosomal anomalies which can be detected by array comparative genomic hybridization (CGH) technique. We analyzed the association of the results of these studies with clinical prognosis and tumor localization. We included 53 patients (18 cerebellar, 20 chiasmatic/hypothalamic and 15 hemispheric). Samples were studied from paraffin embedded tumors.

RESULTS

We found that PAs are mostly diploid and ploidy pattern does not affect the prognosis. The expression of p53, p16, pRb, MMAC/PTEN1 and VEGF was not significantly different between different localizations and could not predict the prognosis. Frequently seen copy number aberrations (CNAs) are: amplification in 1p36.33, 2p11.2, 9p11.2, 9q12, 16p11.2, 19q13.12-q13.2, Xp22.2-p21.3, Xp11.3-p11.22, Xq11.1-q12, Xq13.1, Xq21.1-q21.31, Xq22.3, Xq26.3 and homozygous deletion in 2p11.2, 8p23.1, 16p12.3. Among them, 2p11.2 amp, 9p11.2 amp and 1p36.21 hom del were correlated with prognosis. Moreover, we found a significant correlation between 16p11.2 amp and tumor localization.

CONCLUSIONS

Differently localized PAs have different properties which make them behave with different biological aggressiveness. PAs demonstrate a significant amount of CNAs that can be detected by a high-resolution study. However, tumor suppressor genes p53, p16, pRb, MMAC/PTEN1 and expression patterns do not play a significant role in PAs.

Pilocytic astrocytoma survival in adults: analysis of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute

Pilocytic astrocytoma is a WHO grade 1 brain tumor common in children. Relatively little is known about the behavior of pilocytic astrocytomas in adult patients, largely due to the rarity of pilocytic astrocytoma in this population. Some data suggest that adults share the excellent prognosis seen in children, while other reports suggest more aggressive tumor behavior in adult patients. Patients diagnosed with pilocytic astrocytoma between 1973 and 2008 were identified in the National Cancer Institute Surveillance, Epidemiology, and End Results Program database. Age-group specific survival was analyzed with overall, expected, and cancer-specific survival rates. Further survival analyses were performed with the Kaplan-Meier method and Cox Proportional Hazards models. 3,066 patients with pilocytic astrocytoma were identified, including 865 patients aged 20 years and older. Survival rates declined significantly with age, from 96.5% 60-month survival in patients 5-19 years (95% CI 95.3-97.4) to 52.9% 60-month survival in adult patients 60+ years of age (95% CI 38.4-65.5), with a corresponding decrease in relative and cancer-specific survival rates. Gross total resection was a positive prognostic indicator in adults, while patients receiving radiation had shorter survival regardless of extent of resection. Pilocytic astrocytoma is associated with higher mortality in adult patients than in children and teens, and survival decreases with increasing age in adults. The morbidity of pilocytic astrocytoma in adults provides rationale for future trials of adjuvant treatment in high-risk patients.

BRAF alterations in primary glial and glioneuronal neoplasms of the central nervous system with identification of 2 novel KIAA1549:BRAF fusion variants

Recent studies highlight the importance of BRAF alterations resulting in mitogen activated protein kinase (MAK/ERK) pathway activation in low-grade CNS tumors. We studied 106 low-grade CNS neoplasms in a cohort of primarily pediatric patients to identify the prevalence and clinicopathologic significance of these alterations. Polymerase chain reaction testing identified KIAA1549:BRAF fusions in 51 (48%) tumors overall, including 42 (60%) pilocytic astrocytomas, 4 (17%) unclassifiable low-grade gliomas, 4 (36%) low-grade glioneuronal/neuroepithelial tumors, 0 (of 5) pleomorphic xanthoastrocytomas, 0 (of 4) diffuse astrocytomas (World Health Organization grade II), and 1 (of 3, 33%) pilomyxoid astrocytoma. KIAA1549:BRAF gene fusions confirmed by sequencing included the previously reported ones involving exons 1-16/9-18 (49%), 1-15/9-18 (35%), and 1-16/11-18 (8%) and 2 fusions with novel breakpoints: 1-15/11-18 (6%) and 1-17/10-18 (1%). DNA sequencing identified BRAF mutations in 8% of tumors. BRAF mutations were absent. KIAA1549:BRAF fusions were significantly more frequent in infratentorial (57%) and optic pathway (59%) tumors versus supratentorial (19%) tumors (p = 0.001). We did not identify significantly improved progression-free survival in tumors with fusions. In summary, KIAA1549:BRAF fusions predominate in pilocytic astrocytomas but are also present in some low-grade unclassifiable gliomas and glioneuronal tumors. The prognostic and therapeutic significance of this alteration is unclear and merits further study.

Primary neurosurgery for pediatric low-grade gliomas: a prospective multi-institutional study from the Children's Oncology Group

BACKGROUND

Central nervous system neoplasms are the most common solid tumors in children, and more than 40% are low-grade gliomas. Variable locations, extent of resection, postoperative neurodiagnostic evaluation, and histology have confounded therapy and outcome.

OBJECTIVES

To investigate disease control and survival after surgery.

METHODS

A prospective natural history trial from 1991 to 1996 produced a subset of patients with low-grade gliomas managed by primary surgery and subsequent observation. Patients were evaluable if eligibility, tumor location, and extent of resection were confirmed by pathological diagnosis, preoperative and postoperative imaging, and the surgeon's report. Primary end points were overall survival (OS), progression-free survival (PFS), and postprogression survival.

RESULTS

Of 726 patients enrolled, 518 were fully evaluable for analysis. The 5- and 8-year OS rates were 97% ± 0.8% and 96% ± 0.9%, respectively, and PFS rates were 80% ± 1.8% and 78% ± 2.0%. In univariate analyses, histological type, extent of residual tumor, and disease site were significantly associated with PFS and OS. In multivariate analysis, gross total resection (GTR) without residual disease was the predominant predictor of PFS. In patients with limited residual disease, 56% were free of progression at 5 years.

CONCLUSION

GTR should be the goal when it can be achieved with an acceptable functional outcome. The variable rate of progression after incomplete resection highlights the need for new predictors of tumor behavior.

Vascular endothelial growth factor receptor 2 (VEGFR-2) signalling activity in paediatric pilocytic astrocytoma is restricted to tumour endothelial cells

AIMS

Tumours depend on angiogenesis for enhanced tumour cell survival and progression. Vascular endothelial growth factor receptor (VEGFR) signalling plays a major part in this process. Previously, we evaluated tyrosine kinase activity in paediatric brain tumour tissue lysates using a peptide microarray containing 144 different tyrosine kinase peptide substrates. When applied to paediatric pilocytic astrocytoma tissue, this analysis revealed extensive phosphorylation of VEGFR-derived peptides. The aim of the current study was to validate this result and determine the presence of VEGFR-2 activity in paediatric pilocytic astrocytoma as the main VEGFR in terms of mitogenic signalling. In addition, the localization of VEGFR1-3 mRNA expression was assessed.

METHODS

VEGFR-2 phosphorylation was determined by adopting a proximity ligation assay approach. Enrichment of endothelial markers and VEGFRs in tumour endothelium was determined by quantitative polymerase chain reaction (qPCR) analysis of laser-microdissected blood vessels.

RESULTS

Proximity ligation assays on tumour cryosections showed the presence of phosphorylation of VEGFR-2, which primarily localized to vascular endothelium. qPCR analysis of endothelial markers and VEGFRs showed a 13.6-fold average enrichment of VEGFR-2 expression in the laser-microdissected endothelium compared to whole tumour. Also the expression of VEGFR-1 and -3 was highly enriched in the endothelium fraction with an average fold-enrichment of 16.5 and 50.8 respectively.

CONCLUSIONS

Phosphorylated VEGFR-2 is detected on endothelial cells in paediatric pilocytic astrocytoma. Furthermore, endothelial cells are the main source of VEGFR1-3 mRNA expression. This suggests a crucial role for VEGF/VEGFR-induced angiogenesis in the progression and maintenance of these tumours.

Stereotactic radiosurgery for recurrent or unresectable pilocytic astrocytoma

PURPOSE

To report the outcomes in patients with recurrent or unresectable pilocytic astrocytoma (PA) treated with Gamma Knife stereotactic radiosurgery (SRS).

METHODS AND MATERIALS

Retrospective review of 18 patients (20 lesions) with biopsy-confirmed PA having SRS at our institution from 1992 through 2005.

RESULTS

The median patient age at SRS was 23 years (range, 4-56). Thirteen patients (72%) had undergone one or more previous surgical resections, and 10 (56%) had previously received external-beam radiation therapy (EBRT). The median SRS treatment volume was 9.1 cm(3) (range, 0.7-26.7). The median tumor margin dose was 15 Gy (range, 12-20). The median follow-up was 8.0 years (range, 0.5-15). Overall survival at 1, 5, and 10 years after SRS was 94%, 71%, and 71%, respectively. Tumor progression (local solid progression, n = 4; local solid progression + distant, n = 1; distant, n = 2; cyst development/progression, n = 4) was noted in 11 patients (61%). Progression-free survival at 1, 5, and 10 years was 65%, 41%, and 17%, respectively. Prior EBRT was associated with inferior overall survival (5-year risk, 100% vs. 50%, p = 0.03) and progression-free survival (5-year risk, 71% vs. 20%, p = 0.008). Nine of 11 patients with tumor-related symptoms improved after SRS. Symptomatic edema after SRS occurred in 8 patients (44%), which resolved with short-term corticosteroid therapy in the majority of those without early disease progression.

CONCLUSIONS

SRS has low permanent radiation-related morbidity and durable local tumor control, making it a meaningful treatment option for patients with recurrent or unresectable PA in whom surgery and/or EBRT has failed.

Long-term Follow-up of Pediatric Benign Cerebellar Astrocytomas

BACKGROUND

The long-term prognosis of cerebellar astrocytomas needs to be reviewed.

OBJECTIVE

To elucidate the factors influencing tumor recurrence or progression and to determine how long these patient with cerebellar astrocytomas require surveillance with neuroimaging.

METHODS

A retrospective review of 101 children surgically treated for a cerebellar astrocytoma and followed up for &lt; 10 years was performed.

RESULTS

Mean follow-up was 18.4 years. Total resection confirmed by postoperative imaging was performed in 51 patients (50.5%; group A). Twenty-three patients (22.8%) had surgical total resection; however, equivocal residual tumor was found on postoperative imaging (group B). Subtotal resection leaving a portion of brainstem or cerebellar peduncle was performed in 27 patients (26.7; group C). Of these 50 residual tumors, 16 (32%) showed spontaneous regression and 8 (16%) showed arrested growth. Radiographic recurrence or progression was noted in 29 patients (28.7%). Only 3 of 51 patients (5.9%) of group A with total resection had recurrence, whereas 26 of 50 residual tumors (52%; groups B and C) progressed. The only factor affecting recurrence or progression by multivariate analysis was the extent of surgical resection. All tumor recurrence or progression except for 1 (96.6%) occurred within 8 years from the original surgery (range, 2–132 months).

CONCLUSIONS

Overall prognosis of cerebellar astrocytomas is good; the 10-year survival rate was 100% and recurrence- or progression-free rate was 71.3% in our cohort. Almost half of residual tumors showed spontaneous regression or arrested growth in the long term. Eight to 10 years is considered to be a reasonable follow-up period by neuroimaging.

Pediatric cerebellar pilomyxoid-spectrum astrocytomas

OBJECT

Pediatric cerebellar astrocytomas with pilomyxoid features include classic pilomyxoid astrocytomas (PMAs) and intermediate pilomyxoid tumors (IPTs). Since the original description of PMA in 1999, most reports in the literature have described PMAs arising from the hypothalamic/chiasmatic region. To the authors' knowledge, PMAs arising from the posterior fossa have not been discussed in the neurosurgical literature. Intermediate pilomyxoid tumors, or tumors with pathological features of both pilocytic astrocytoma (PA) and PMA, have only recently been described. In this article, the authors present 2 cases that fall within the spectrum of pediatric cerebellar PMA-including a classic PMA and an intermediate pilomyxoid tumor. The authors compare the radiological presentation, surgical results, and postoperative course to findings in a cohort of 15 patients with cerebellar PAs.

METHODS

Between 2003 and 2010, 2 patients with pilomyxoid-spectrum astrocytomas underwent treatment at Vanderbilt Children's Hospital. One was a 22-month-old girl who presented with progressive gait disturbance and falls. The other was a 4-year-old girl who presented with ataxia and generalized weakness. In a retrospective review of pediatric cerebellar neoplasms resected by the senior author during this period, these tumors comprised 4% of cerebellar neoplasms and approximately 10% of cerebellar glial neoplasms.

RESULTS

Both patients were treated with midline suboccipital craniotomy for resection. In both cases, tumor invasion anteriorly into the brainstem prevented gross-total resection. the patient in Case 1 was placed on chemotherapy following pathological diagnosis and later developed definitive evidence of leptomeningeal dissemination (LD) 3 years after the operation. The patient in Case 2 was placed on chemotherapy after exhibiting progressive evidence of local recurrence (findings were negative for LD) 12 months following resection.

CONCLUSIONS

Pediatric patients with cerebellar pilomyxoid-spectrum astrocytomas appear to suffer higher rates of local recurrence and LD than pediatric patients with cerebellar PAs.

An activated mutant BRAF kinase domain is sufficient to induce pilocytic astrocytoma in mice

Pilocytic astrocytoma (PA) is the most common type of primary brain tumor in children and the second most frequent cancer in childhood. Children with incompletely resected PA represent a clinically challenging patient cohort for whom conventional adjuvant therapies are only moderately effective. This has produced high clinical demand for testing of new molecularly targeted treatments. However, the development of new therapeutics for PA has been hampered by the lack of an adequate in vivo tumor model. Recent studies have identified activation of MAPK signaling, mainly by oncogenic BRAF activation, as a hallmark genetic event in the pathogenesis of human PA. Using in vivo retroviral somatic gene transfer into mouse neural progenitor cells, we have shown here that ectopic expression of the activated BRAF kinase domain is sufficient to induce PA in mice. Further in vitro analyses demonstrated that overexpression of activated BRAF led to increased proliferation of primary mouse astrocytes that could be inhibited by treatment with the kinase inhibitor sorafenib. Our in vivo model for PA shows that the activated BRAF kinase domain is sufficient to induce PA and highlights its role as a potential therapeutic target.

Tumour vasculature and angiogenic profile of paediatric pilocytic astrocytoma; is it much different from glioblastoma?

AIMS

Pilocytic astrocytomas are the most frequent brain tumours in children. Because of their high vascularity, this study aimed to obtain insights into potential angiogenic related therapeutic targets in these tumours by characterization of the vasculature and the angiogenic profile. In this study 59 paediatric pilocytic astrocytomas were compared with 62 adult glioblastomas, as a prototype of tumour angiogenesis.

METHODS

Microvessel density, vessel maturity in terms of basement membrane and pericyte coverage, and turnover of both endothelial and tumour cells, and vascular endothelial growth factor (VEGF) expression were evaluated in tumour tissue, immunohistochemically stained with, respectively, CD34, collagen IV, smooth muscle actin, Ki67/CD34, caspase-3/CD34 and VEGF(-A-D). As an indicator for vessel stability the angiopoietin (ANGPT)-1/ANGPT-2 balance was calculated using Real Time RT-PCR.

RESULTS

Pilocytic astrocytoma and glioblastoma showed similar fractions of vessels covered with basement membrane and pericytes. Overlapping ANGPT-1/ANGPT-2 balance and VEGF-A expression were found. Pilocytic astrocytoma had fewer but wider vessels compared with glioblastoma. Turnover of endothelial and tumour cells were relatively lower in pilocytic astrocytoma. Within pilocytic astrocytoma, higher ANGPT-1/ANGPT-2 balance was correlated with fewer apoptotic endothelial cells. Lower numbers of vessels were correlated with higher VEGF-A expression.

CONCLUSIONS

Despite the fact that pilocytic astrocytoma showed a different vessel architecture compared with glioblastoma, a critical overlap in vessel immaturity/instability and the angiogenic profile was seen between both tumours. These findings suggest encouraging possibilities for targeting angiogenesis (for instance with anti-VEGF) as a therapeutic strategy in pilocytic astrocytoma.

PI3K/AKT pathway alterations are associated with clinically aggressive and histologically anaplastic subsets of pilocytic astrocytoma

Pilocytic astrocytomas (PA) are well-differentiated gliomas having a favorable prognosis when compared with other diffuse or infiltrative astrocytomas. Molecular genetic abnormalities and activation of signaling pathways associated with clinically aggressive PA and histologically anaplastic PA have not been adequately studied. We performed molecular genetic, gene expression, and immunohistochemical studies using three PA subsets, including conventional PA (n = 43), clinically aggressive/recurrent PA (n = 24), and histologically anaplastic PA (n = 25). A clinical diagnosis of NF1 was present in 28% of anaplastic PA. Molecular cytogenetic studies demonstrated heterozygous PTEN/10q and homozygous p16 deletions in 6/19 (32%) and 3/15 (20%) cases of anaplastic PA, respectively, but in neither of the two other groups. BRAF duplication was identified in 33% of sporadic anaplastic PA and 63% of cerebellar examples. BRAF (V600E) mutation was absent in four (of 4) sporadic cases lacking duplication. IDH1(R132H) immunohistochemistry was negative in 16 (of 16) cases. Neither PDGFRA nor EGFR amplifications were present. pERK staining levels were similar among the three PA subsets, but a stepwise increase in cytoplasmic pAKT and to a lesser extent pS6 immunoreactivity was noted by immunohistochemistry in aggressive PA groups. This was particularly true in histologically anaplastic PA when compared with conventional PA (p < 0.001 and p = 0.005, respectively). In addition, PTEN expression at the mRNA level was decreased in histologically anaplastic PA when compared to the other groups (p = 0.05). In summary, activation of the PI3K/AKT in addition to MAPK/ERK signaling pathways may underlie biological aggressiveness in PA. Specifically, it may mediate the increased proliferative activity observed in histologically anaplastic PA.

Predictive factors for early symptomatic recurrence in pilocytic astrocytoma: does angiogenesis have a role to play?

We studied predictive factors with respect to angiogenesis and proliferative indices for early symptomatic recurrences in patients with pilocytic astrocytoma (PA). One hundred and eighteen patients who underwent surgery for PA were divided into non-recurrent and early symptomatic recurrence groups to analyze clinicoradiological and immunohistopathological (n=33) parameters. Patients with non-recurrent tumors presented with symptoms for a mean duration of 10.2 ± 9.1 months while those with recurrent tumors presented slightly earlier (6.9 ± 4.5 months). Common tumor locations were the cerebellum (38.1%), optic chiasm (27.9%), supratentorial region (19.4%) and brainstem (9.3%). Recurrent tumors were mostly located in the cerebellum (44%) and brainstem (33%). Strong contrast enhancement was noted in 70 (59.3%) tumors, while 48 (40.7%) showed poor contrast. Resection was complete in 53% of patients while near total excision was achieved for the remaining patients. Cellularity and pleomorphism were similar in both groups. Extensive endothelial proliferation was observed in 18.1% of patients while the remainder showed a focal pattern. Diffuse vascular endothelial growth factor (VEGF) expression was observed in 36.3% of patients while 63.6% showed mild-to-moderate focal expression. Endothelial proliferation and VEGF expression were more pronounced in patients with non-recurrent tumors, but this was not statistically significant. MIB-I labeling indices were similar (1-5%) for both groups. Symptomatic recurrences were common in infratentorial PAs. Radiology, histopathology and proliferative indices did not offer any prognostic information. Angiogenesis markers such as endothelial proliferation and VEFG expression did not predict early symptomatic recurrence. Diffuse VEGF expression and endothelial proliferation were observed in tumors that showed strong contrast enhancement.

Use of T2 signal intensity of cerebellar neoplasms in pediatric patients to guide preoperative staging of the neuraxis

OBJECT

The question of whether to obtain routine or selective preoperative imaging of the neuraxis in pediatric patients with cerebellar neoplasms remains a controversial topic. Staging of the neuraxis is generally considered beneficial in patients with neoplasms associated with an elevated risk of leptomeningeal dissemination (LD). When these studies are obtained preoperatively, there is a decrease in the number of false-positive images related to debris in the immediate postoperative period. Additionally, knowledge of the extent of spread has the potential to affect the risk/benefit analysis of aggressive resection. Although the majority of pediatric neurosurgeons surveyed choose to obtain selective preoperative imaging of the neuraxis in cases of cerebellar neoplasms "with findings suggestive of high-grade pathology," an evidence-based protocol in the literature is lacking. The goal of this study was to assess radiological characteristics of tumors with an elevated risk of LD and identify a method to help guide preoperative imaging of the neuraxis.

METHODS

The authors first reviewed the literature to gain an appreciation of the risk of LD of pediatric cerebellar neoplasms based on underlying histopathology and/or grade. Available evidence indicates preoperative imaging of the neuraxis in patients with Grade I tumors to be of questionable utility. In contrast, evidence suggested that preoperative imaging of the neuraxis in patients with Grades II-IV neoplasms was clinically warranted. The authors then evaluated an extensive base of neuroradiological literature to identify possible MR imaging and/or CT findings with the potential to differentiate Grade I from higher-grade neoplasms in pediatric patients. They analyzed the preoperative radiological findings in 50 pediatric patients who had undergone craniotomy for resection of cerebellar neoplasms at Vanderbilt Children's Hospital since 2003 with reference to 7 chosen radiological criteria. Logistic regression models were fit using radiological features to determine the best predictors of Grades II-IV tumors. Receiver operating characteristic methods were used to identify diagnostic properties of the best predictors.

RESULTS

The relative T2 signal intensity (RT2SI), an indirect measure of the water content of the solid component of the tumor, was best able to identify neoplasms with an elevated risk of LD. An RT2SI value of 0.71 was selected by the authors as the best operating point on the curve. Of the 31 neoplasms retrospectively designated as hypointense T2-weighted lesions (RT2SI ≤ 0.71), 30 (97%) were Grade II or higher. All medulloblastomas, ependymomas, and high-grade (Grades III and IV) neoplasms were hypointense T2-weighted lesions. Of the 19 T2-weighted hyperintense neoplasms (RT2SI > 0.71), 16 (84%) were Grade I and 3 were Grade II.

CONCLUSIONS

Measurement of the RT2SI can help predict Grade II-IV tumors at an elevated risk of leptomeningeal spread and guide staging of the neuraxis. Pediatric patients with cerebellar neoplasms found to have an RT2SI of less than or equal to 0.71 are recommended for neuraxis imaging prior to surgery.

Posterior fossa ependymomas: new radiological classification with surgical correlation

PURPOSE

The key determinant of long-term outcome in infratentorial ependymomas remains the extent of surgical resection. We describe a new radiological classification system which is validated against surgical findings and correlated with risk of post-operative residual tumour.

METHODS

Twenty-five consecutive patients (12 females, mean age 4.9 years, range 0.5-17 years) with infratentorial ependymomas were studied. Lesions were classified on pre-operative MRI according to the pattern of extension, brainstem displacement and involvement of the obex, as lateral-type or midfloor-type tumours. Twenty-one operative records were reviewed with respect to the microanatomical tumour origin by a paediatric neurosurgeon, blinded to MRI findings. Follow-up imaging studies were evaluated for residual tumour.

RESULTS

There were 15 cases of midfloor-type tumour (anterior displacement of brainstem, infiltration of obex) and 10 cases of lateral-type tumour (lateral displacement of brainstem, obex free of tumour). Extension into prepontine or cerebellopontine cisterns was more common in lateral-type tumours. Agreement between the radiological classification and tumour origin, as defined by operative records, was seen in 18 out of 20 cases. Risk of residual tumour in lateral-type tumours was more than twice that of midfloor-type tumours (80% vs. 33%, p=0.04). Risk of tumour residual was also significantly higher when vessel encasement or prepontine extension was observed.

CONCLUSIONS

Infratentorial ependymomas can be pre-operatively classified as lateral-type or midfloor-type tumours. This correlates well with operative findings. Lateral-type tumours have significantly increased risk of residual tumour compared to midfloor- type tumours and this may influence intensity of imaging surveillance.

Pilocytic astrocytomas have telomere-associated promyelocytic leukemia bodies without alternatively lengthened telomeres

Telomere maintenance by either telomerase activity or the recombination-mediated alternative lengthening of telomeres (ALT) mechanism is a hallmark of cancer. Tumors that use ALT as their telomere maintenance mechanism are characterized by long telomeres of great heterogeneity in length and by specific nuclear structures of co-localized promyelocytic leukemia protein and telomere DNA, called ALT-associated promyelocytic leukemia bodies (APBs). Recent advances have revealed a direct role for APBs in telomere recombination in ALT-positive cells. In this study, we investigated the possibility that APBs could occur before the long 'alternatively' lengthened telomeres arise, particularly in low-grade tumors. We measured APBs, telomere length, and telomerase activity in 64 astrocytomas inclusive of grade 1-4 tumors. Almost all grade 1-3 tumors (93%) were APB-positive using published criteria. Grade 2-3 APB-positive tumors also had long telomeres and were confirmed as ALT positive. However, grade 1 tumors lacked long telomeres and were therefore classified as ALT negative, but positive for telomere-associated promyelocytic leukemia bodies (TPB). This is the first report of a TPB-positive but ALT-negative tumor, and suggests that low-grade tumors have the foundation for recombinational telomere repair, as in ALT. Further work is warranted to characterize the TPB-positive phenotype in other early malignancies, as well as to determine whether TPBs predispose to telomere maintenance by ALT.

Postoperative imaging surveillance in pediatric pilocytic astrocytomas

OBJECT

Currently there is no consensus regarding the frequency of neuroimaging following gross-total resection (GTR) of pilocytic astrocytoma (PA) in children. Whereas several reports recommend no postoperative imaging, one study proposed surveillance MR imaging studies to detect delayed recurrences.

METHODS

The records of 40 consecutive pediatric patients who underwent GTR of infratentorial PAs were examined. All had follow-up duration of ≥ 2 years. Patients underwent early (< 48 hours) postoperative MR imaging, followed by surveillance imaging at 3-6 months, 1 year, and variably thereafter. The classification of GTR was based on a lack of nodular enhancement on early postoperative MR imaging. Demographic, clinical, and pathological variables were analyzed with respect to recurrence status. Univariate and multivariate analyses were performed to evaluate the association between pathological variables and recurrence-free survival (RFS).

RESULTS

Of 13 patients demonstrating new nodular enhancement on MR imaging at 3-6 months, the disease progressed in 10, with a median time to recurrence of 6.4 months (range 2-48.2 months). At last follow-up, 29 patients had no recurrence, whereas in 1 additional patient the tumor recurred at 48 months, despite the absence of a new contrast-enhancing nodule at 3-6 months (for a total of 11 patients with recurrence). No demographic variable was associated with recurrence. Nodular enhancement on MR imaging at 3-6 months was significantly associated with recurrence in both univariate (p < 0.0001) and multivariate (p = 0.0015) analyses. Among the pathological variables, a high Ki 67 labeling index (LI) was similarly significantly associated with RFS in both univariate (p = 0.0016) and multivariate (p = 0.034) analyses. Multivariate models that significantly predicted RFS included a risk score incorporating Ki 67 LI and CD68 positivity (p = 0.0022), and a similar risk score combining high Ki 67 LI with the presence of nodular enhancement on initial surveillance MR imaging (p < 0.0001).

CONCLUSIONS

Surveillance MR imaging at 3-6 months after resection predicts tumor recurrence following GTR. One patient suffered delayed recurrence, arguing against a "no imaging" philosophy. The data also highlight the pathological variables that can help categorize patients into groups with high or low risk for recurrence. Larger series are needed to confirm these associations.

Association of molecular alterations, including BRAF, with biology and outcome in pilocytic astrocytomas

Pilocytic astrocytoma (PA) is the most common glioma in the pediatric population. PAs can exhibit variable behavior that does not always correlate with location. Although oncogenic rearrangements of the BRAF gene have recently been described in PAs, it is not clear whether such alterations have an impact on outcome. An institutional cohort of 147 PAs (118 with outcome data) from both cerebellar and non-cerebellar locations (spine, diencephalon, midbrain, brainstem, and cortex) was utilized in this study. Parameters included quantification of characteristic morphologic variables as well as genes and molecular loci previously shown to be of relevance in high-grade gliomas, including 1p, 9p, 10q, 17p, 19q, and BRAF. Neither 1p, 9p, and 10q nor 19q showed significant association with outcome in PAs, although p16 deletion was more common in PAs of the midbrain, brainstem, and spinal cord. Loss of heterozygosity on 17p13 correlated with increased risk of recurrence in cerebellar tumors. BRAF gene rearrangements were more common in cerebellar tumors than non-cerebellar tumors and associated with classic biphasic histology in the cerebellum. However, clinical outcome was independent of BRAF status. The molecular biology of PAs differs according to location, yet BRAF rearrangements do not appear to produce PAs with different behavior. Nevertheless, such tumors may have altered sensitivity to pathway-specific adjuvant therapy. Additionally, deletion on 17p13 may be an adverse prognostic biomarker in cerebellar tumors.

In pursuit of prognostic factors in children with pilocytic astrocytomas

OBJECTIVE

This study described a 23-year experience in the treatment of children with pilocytic astrocytomas (piloA) with the aim of identifying putative clinical, histopathological, and/or immunohistochemical features that could be related to the outcome of these patients.

METHODS

Clinical data of 31 patients under 18 years of age with piloA were obtained from 1984 to 2006.

RESULTS

The mean age at the time of surgery was 7.8 +/- 4.2 years (1 to 17 years), and the mean follow-up was 5.7 +/- 5.4 years (1 to 20 years). The most common site of tumor formation was the cerebellum (17), followed by brainstem (4), optic chiasmatic hypothalamic region (4), cerebral hemisphere (3), cervical spinal cord (2), and optic nerve (1). Gross total resection (GTR) was achieved in 23 (74.1%), mainly in those with tumors located in the cerebellum and cerebral hemispheres (P = 0.02). The global mortality rate was 6.4%. Nine patients were reoperated. Rosenthal fibers, eosinophilic granular bodies, microvascular proliferation, and lymphocytic infiltration were observed in most cases. The mean Ki-67LI was 4.4 +/- 4.5%. In all cases, Gal-3 expression in tumor cells was observed with variable staining pattern.

CONCLUSIONS

Aside from GTR, no other clinical, histopathological, or immunohistochemical features were found to be related to the prognosis. We postulate that strict follow-up is recommended if piloA is associated with high mitotic activity/Ki67-LI, or if GTR cannot be achieved at surgery. Tumor recurrence or progression of the residual lesion should be strictly observed. In some aspects, childhood piloA remains an enigmatic tumor.