Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Pediatric gliomas

Pediatric gliomas comprise a clinically, histologically, and molecularly very heterogeneous group of CNS tumors. In addition, these tumors are largely different from their counterparts occurring in adults, although they are histologically indistinguishable and uniformly classified by the current WHO classification for CNS tumors. Pilocytic astrocytoma (WHO grade I), mainly arising in the posterior fossa, is the most common representative in children, whereas glioblastoma multiforme (WHO grade IV) predominates in adults. When radical surgical resection is possible in low-grade gliomas, it will likely cure the patient. If complete surgical resection is not possible, however, for example in brainstem gliomas, which are defined by their anatomic localization rather than by their histological or molecular features, therapeutic options are limited and prognosis is usually poor. Recent genome-wide analyses applying different microarray-based methods to investigate DNA copy-number aberrations, mRNA expression signatures, and methylation patterns have shed some light on the pathways involved in the pathogenesis of pediatric glio-mas. Mitogen-activated protein kinase (MAPK) and PI3K/AKT signaling were identified as prominent oncogenic pathways in astrocytic tumors in several studies, whereas NOTCH signaling was implicated in the pathogenesis of a subset of intracranial ependymomas. Future therapeutic strategies targeting these (and other) pathways or conferring epigenetic modifications in the tumor might contribute to a better treatment outcome of patients with unresectable or disseminated tumors at diagnosis. Consideration of reliable molecular markers for outcome prediction will most likely result in a better stratification of patients into different risk groups with adjusted treatment intensity in the future.

Neurofibromatosis type 1 revisited

Neurofibromatosis type 1 (NF1) is an autosomal dominant condition with a worldwide incidence of approximately 1 per 2500 to 3000 individuals. Caused by a germ-line-inactivating mutation in the NF1 gene on chromosome 17, the disease is associated with increased morbidity and mortality. In the past several years, significant progress has been made in standardizing management of the major clinical features of neurofibromatosis type 1. Moreover, improved understanding of how the neurofibromatosis type 1 protein, neurofibromin, regulates cell growth recently provided insight into the pathogenesis of the disease and has led to the development of new therapies. In this review, we describe the clinical manifestations, recent molecular and genetic findings, and current and developing therapies for managing clinical problems associated with neurofibromatosis type 1.

Diffusion-weighted and dynamic contrast-enhanced imaging as markers of clinical behavior in children with optic pathway glioma

BACKGROUND

Optic pathway gliomas (OPGs) are common pediatric brain tumors that pose significant clinical challenges with regard to predicting which tumors are likely to become symptomatic and require treatment. These tumors can arise sporadically or in the context of the inherited cancer predisposition syndrome neurofibromatosis type 1 (NF1). Few studies have suggested biological or imaging markers that predict the clinical course of this disease.

OBJECTIVE

In this cross-sectional study, we hypothesized that the clinical behavior of OPGs in children can be differentiated by diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) MRI.

MATERIALS AND METHODS

A total of 27 children with OPG were studied using DW and DCE MRI protocols. Diffusivity and permeability were calculated and correlated with the clinical behavior the OPG.

RESULTS

Mean diffusivity values of 1.39 microm2/ms and mean permeability values of 2.10 ml/min per 100 cm3 of tissue were measured. Clinically aggressive OPGs had significantly higher mean permeability values (P = 0.05) than clinically stable tumors. In addition, there was a strong correlation between clinical aggressiveness and the absence of NF1 (P < 0.01).

CONCLUSION

These results suggest that DCE MRI might be a useful biomarker for clinically aggressive OPG, which should be confirmed in larger prospective longitudinal studies.

BRAF gene duplication constitutes a mechanism of MAPK pathway activation in low-grade astrocytomas

The molecular pathogenesis of pediatric astrocytomas is still poorly understood. To further understand the genetic abnormalities associated with these tumors, we performed a genome-wide analysis of DNA copy number aberrations in pediatric low-grade astrocytomas by using array-based comparative genomic hybridization. Duplication of the BRAF protooncogene was the most frequent genomic aberration, and tumors with BRAF duplication showed significantly increased mRNA levels of BRAF and a downstream target, CCND1, as compared with tumors without duplication. Furthermore, denaturing HPLC showed that activating BRAF mutations were detected in some of the tumors without BRAF duplication. Similarly, a marked proportion of low-grade astrocytomas from adult patients also had BRAF duplication. Both the stable silencing of BRAF through shRNA lentiviral transduction and pharmacological inhibition of MEK1/2, the immediate downstream phosphorylation target of BRAF, blocked the proliferation and arrested the growth of cultured tumor cells derived from low-grade gliomas. Our findings implicate aberrant activation of the MAPK pathway due to gene duplication or mutation of BRAF as a molecular mechanism of pathogenesis in low-grade astrocytomas and suggest inhibition of the MAPK pathway as a potential treatment.

Extraventricular neurocytoma in neurofibromatosis Type 1: case report

Neurocytomas are rare tumors of the central nervous system that are typically located in the ventricular system. The authors report a case of a child with neurofibromatosis Type 1 (NF1) who had a tumor of the optic nerves and chiasm with signal abnormality extending through the diencephalon, as well as an occipital lobe mass, which was presumed to be part of the visual pathway neoplasm. Because the occipital lobe lesion slowly increased in size over time, while the other areas remained stable, a biopsy was performed. Pathological evaluation revealed an extraventricular neurocytoma of extraventricular neurocytoma. To the authors' knowledge, neurocytomas have not been previously reported in patients with NF1. Because visual pathway gliomas are extremely common in children with NF1, they are often treated empirically as low-grade gliomas without histological confirmation. The importance of obtaining a biopsy in lesions that have atypical imaging features is highlighted.

Assessment of chemotherapeutic response in children with proptosis due to optic nerve glioma

INTRODUCTION

Some children with optic pathway gliomas present with proptosis related to intraorbital tumor extension. The radiological assessment of chemotherapeutic response in these patients can be complicated by irregular tumor shape and lack of relation between tumor volume and cosmetic effect.

METHOD

We propose that proptosis measurements and derivation of a proptosis index can be a useful adjunct to the measurement of tumor volume in the radiological assessment of chemotherapeutic response. The proptosis index was derived as the ratio of the difference in proptosis between eyes postchemotherapy to that prechemotherapy. A series of six patients with proptosis and the diagnosis of an optic nerve tumor from an optic pathway glioma registry demonstrate by case example the correlation between the proptosis index and the clinical and radiographic response to chemotherapy.

CONCLUSIONS

We have found that a proptosis index <1 correlates with a chemotherapeutic maintained response and an index >1 correlates with progressive disease.

Gliomas in neurofibromatosis type 1: a clinicopathologic study of 100 patients

There are few pathologic studies of gliomas in patients with neurofibromatosis type 1. We analyzed clinical and pathologic features of gliomas from 100 neurofibromatosis type 1 patients (57 men; 43 women). The median age at tumor diagnosis was 13 years (range, 4 months to 68 years). Most tumors were typical pilocytic astrocytoma (PA) (49%) or diffusely infiltrating astrocytoma (DA) (27%) that included World Health Organization Grades II (5%), III (15%), and IV (7%); others were designated as low-grade astrocytoma, subtype indeterminate (LGSI; 17%). Two pilomyxoid astrocytomas, 1 desmoplastic infantile ganglioglioma and 1 conventional ganglioglioma, were also identified. The tumors in 24 cases arose in the optic pathways and included PA (n = 14), LGSI (n = 4), DA (n = 4), pilomyxoid astrocytoma (n = 1), and ganglioglioma (n = 1). The prognoses of the PA and LGSI gliomas overall were generally favorable; there were no survival differences between PA and LGSI groups based on site, tumor size, mitotic activity, or MIB-1 labeling index. In the combined PA and LGSI group, age younger than 10 years and gross total resection were associated with an increased overall survival rate (p = 0.047 and 0.002, respectively). Compared with the combined group (PA + LGSI), patients with DA at all sites had decreased overall and recurrence-free survival times (p < 0.001 and p = 0.003, respectively). This study emphasizes the wide histologic spectrum of gliomas that occur in patients with neurofibromatosis type 1. Classic PA and LGSI are the most common, and most have favorable prognoses. By contrast, DAs are more aggressive, similar to those that arise sporadically.

Health supervision for children with neurofibromatosis

Neurofibromatosis 1 is a multisystem disorder that primarily involves the skin and nervous system. Its population prevalence is 1 in 3500. The condition usually is recognized in early childhood, when cutaneous manifestations are apparent. Although neurofibromatosis 1 is associated with marked clinical variability, most affected children do well from the standpoint of their growth and development. Some features of neurofibromatosis 1 are present at birth, and others are age-related abnormalities of tissue proliferation, which necessitate periodic monitoring to address ongoing health and developmental needs and to minimize the risk of serious medical complications. This clinical report provides a review of the clinical criteria needed to establish a diagnosis, the inheritance pattern of neurofibromatosis 1, its major clinical and developmental manifestations, and guidelines for monitoring and providing intervention to maximize the growth, development, and health of an affected child.

Electrophysiological monitoring in a patient with an optic nerve glioma

PURPOSE

To report a case illustrating the value of pattern VEP and pattern ERG (PERG) in monitoring optic nerve gliomata (OG).

CASE REPORT

A 15-year-old girl presented with a 3-year history of frontal headaches and a 5-month history of blurred vision in the right eye. MRI scanning revealed a thickened, right optic nerve extending to the cranial opening of the optic canal, consistent with an optic nerve glioma. Pattern VEP showed a mildly delayed major positive component consistent with optic nerve dysfunction. The PERG N95:P50 ratio was subnormal in keeping with retinal ganglion cell involvement. Visual acuity decreased over the following 2 years and repeat VEP objectively demonstrated marked deterioration in optic nerve function despite neuroradiology showing no significant change in the tumour.

CONCLUSIONS

Pattern VEPs and pattern ERGs can provide early objective evidence of optic nerve/retinal ganglion cell dysfunction in optic nerve gliomata. Serial recordings can objectively demonstrate worsening function in the absence of significant neuroradiological change.

GLIOGENE an International Consortium to Understand Familial Glioma

Evidence for familial aggregation of glioma has been documented in both case-control and cohort studies and occurs apart from the well-described rare inherited genetic syndromes involving glioma: neurofibromatosis type 1 and 2, tuberous sclerosis, Turcot's syndrome, and Li-Fraumeni syndrome. Nonsyndromic glioma families have been studied but no genes have been identified in the two published linkage studies of familial glioma probably due to the small number of families. Because glioma is a rare but devastating cancer, and a family history of glioma has been observed in approximately 5% of the cases, we initiated an international consortium to identify glioma families not affected by syndromes to better understand the inherited factors related to this disease. The international consortium GLIOGENE is an acronym for "glioma gene" and includes 15 research groups in North America, Europe, and Israel to study familial glioma. The overarching goal is to characterize genes in glioma families using a genome-wide single-nucleotide polymorphism approach and conducting linkage analysis to identify new genomic regions or loci that could harbor genes important for gliomagenesis. Here, we review the rationale for studying familial glioma and our proposed strategy for the GLIOGENE study.

Syndromic and sporadic pediatric optic pathway gliomas: review of clinical and histopathological differences and treatment implications

✓Optic pathway gliomas (OPGs) are the most common primary neoplasm of the optic pathway. These lesions usually present in childhood and can arise anywhere along the optic pathway; they occur more frequently in women; and they rarely undergo late progression. Management strategies after the initial diagnosis are controversial, compounded by the different behaviors exhibited by sporadic and syndromic tumors. Neurofibromatosis Type 1 (NF1), with aberrant oncogenic signaling and consequent predisposition to intracranial tumors, is the most common associated syndrome, with nearly 20% of NF1 patients developing OPGs. A comorbid NF1 diagnosis has implications for tumor location with greater predilection for optic nerve involvement, whereas chiasmal and postchiasmal lesions are more frequently seen in sporadic cases. Syndromic OPGs often exhibit more indolent behavior and lower rates of clinical progression, and the majority of these are diagnosed by routine neuroophthalmological screening. When treatment is indicated, however, the molecular abnormalities that constitute this syndrome can limit the available chemotherapy and radiotherapy options because clinicians fear secondary malignancy and cerebrovascular complications. Furthermore, radiotherapy early in life can impair an individual's intellectual development, endocrine function, and physical growth, thereby limiting the role of this modality in the treatment of this childhood lesion. Differential gene expression and histogenesis among sporadic and syndromic OPGs may account for the different tumor behaviors, but studies correlating specific genetic and proteomic changes with patient outcome are pending. Loss of heterozygosity at 10 and 17q are more common among patients with NF1, and Ki67 labeling intensity of 2–3% and low p53 labeling intensity seem prognostic of aggressive tumor behavior. Recent advances in the development of a preclinical mouse model of NF1-associated OPG will permit investigation into improved detection strategies and chemotherapeutic and radiotherapy treatment protocols.

Optic pathway gliomas: a review

✓Optic pathway gliomas represent approximately 3–5% of childhood intracranial tumors. They usually occur in children during the first decade of life and are seen in 11–30% of patients with neurofibromatosis Type 1 (NF1). Although these tumors are typically low-grade gliomas, the clinical course and natural history are highly variable, making treatment paradigms difficult. Overall, however, they are often indolent tumors that can be observed over time for progression without initial treatment, especially in patients with NF1. Chemotherapy is the first-line treatment for progressive tumors, and radiation therapy is reserved for patients with progressive disease who are older than 5–7 years. Surgery is reserved for large tumors causing mass effect or hydrocephalus and tumors confined to the orbit or unilateral optic nerve.

Neuroophthalmological management of optic pathway gliomas

✓ The growth rate of optic pathway gliomas (OPGs) is unpredictable and quite variable, especially in children with neurofibromatosis Type 1 (NF1). Close neuroophthalmalogical clinical follow-up with serial imaging (magnetic resonance imaging of the brain with and without contrast enhancement) is the recommended initial step in management to establish the growth rate of the lesion in an individual patient. Typically, only symptomatic and/or radiographically growing tumors require treatment, and observation is the accepted first-line option. Although both chemotherapy and radiotherapy can stabilize growth or even decrease the size of tumors, chemotherapy, especially in younger patients, has fewer side effects than radiation therapy (such as secondary tumors, radiation necrosis, and Moyomoya disease) and is generally considered the first-line treatment for progressive lesions in younger patients. The tumor location defines prognosis in OPGs; optic nerve gliomas (ONG) have the lowest rate of complications and death, and optic chiasm and retrochiasmal gliomas the highest. Although the major complication of an OPG is visual loss, hypothalamic involvement can lead to death. Resection is an option for ONGs but is generally reserved for tumors confined to the optic nerve with poor or no vision, or for patients with severe, cosmetically unappealing proptosis, producing severe pain or exposure keratopathy in a blind eye. Resection is generally not an option for intrinsic chiasmal or retrochiasmal OPGs. Extrinsic (exophytic) components can be debulked surgically, and surgery can be performed for hydrocephalus (ventriculoperitoneal shunt placement). The approach to a patient with OPG must be individualized based on tumor location, radiographic or clinical progression, the presence of NF1, and a risk–benefit comparison for treatment.

Genodermatoses with malignant potential

PURPOSE OF REVIEW

The delineation of syndromes carrying a predisposition to malignancy has led to great insights into the molecular biology of malignancy. Many such syndromes have cutaneous findings which can precede the development of neoplasia. Early recognition of the cutaneous stigmata of the genodermatoses with malignant potential can lead to early diagnosis and initiation of proper screening and treatment when indicated.

RECENT FINDINGS

This article reviews 'classic' genodermatoses with malignant potential and highlights recent recommendations for screening and treatment. Additionally more recently delineated syndromes and their cutaneous findings are discussed.

SUMMARY

Certain inherited syndromes with a risk of neoplasia exhibit characteristic cutaneous findings. Recognition of these findings by the astute practitioner can lead to early intervention which can impact the course of these rare diseases.

Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Optic pathway glioma (OPG), seen in 15% to 20% of individuals with neurofibromatosis type 1 (NF1), account for significant morbidity in young children with NF1. Overwhelmingly a tumor of children younger than 7 years, OPG may present in individuals with NF1 at any age. Although many OPG may remain indolent and never cause signs or symptoms, others lead to vision loss, proptosis, or precocious puberty. Because the natural history and treatment of NF1-associated OPG is different from that of sporadic OPG in individuals without NF1, a task force composed of basic scientists and clinical researchers was assembled in 1997 to propose a set of guidelines for the diagnosis and management of NF1-associated OPG. This new review highlights advances in our understanding of the pathophysiology and clinical behavior of these tumors made over the last 10 years. Controversies in both the diagnosis and management of these tumors are examined. Finally, specific evidence-based recommendations are proposed for clinicians caring for children with NF1.