Genotype/phenotype correlations in type 2 neurofibromatosis (NF2): evidence for more severe disease associated with truncating mutations

High de novo mutation rate in Iranian NF2-related schwannomatosis patients with a report of a novel NF2 mutation

BACKGROUND

NF2-related schwannomatosis (NF2) is a rare genetic disease that significantly impacts patients' quality of life due to the occurrence of multiple tumors within the nervous system. The high clinical heterogeneity in tumor number, location, and size makes predicting each patient's clinical outcome impossible. Genetic investigation can be crucial in diagnosis, prognosis, and management. This study aims to explore the genetic basis of eight Iranian patients with NF2.

METHODS AND RESULTS

To investigate potential genetic causes, we conducted comprehensive medical evaluations, whole-exome sequencing (WES), and multiplex ligation-dependent probe amplification (MLPA) on the probands of each family. The identified variants in the family members were confirmed using Sanger sequencing and MLPA. The variants were classified according to the American College of Medical Genetics and Genomics guidelines. Seven distinct variants linked to the NF2 gene were identified as causes of NF2-related schwannomatosis in these patients, among which the c.862_863del frameshift was a novel variant not previously reported. Seventy-five percent of these mutations were de novo. The mean diagnostic age was lower among patients with truncating mutations compared to other patients.

CONCLUSIONS

This study identified a novel mutation in the NF2 gene and showed a high rate of de novo mutations in Iranian NF2 patients. Moreover, patients with truncating mutations experienced earlier symptoms than others. Comparing the manifestations of each patient with similar mutations to previous reports expands our understanding of the phenotype of NF2. These results can provide more comprehensive insights into prognosis and early interventions.

Update on Cancer and Central Nervous System Tumor Surveillance in Pediatric NF2-, SMARCB1-, and LZTR1-Related Schwannomatosis

Schwannomatosis (SWN) is a distinct cancer predisposition syndrome caused by germline pathogenic variants in the genes NF2, SMARCB1, or LZTR1. There is a significant clinical overlap between these syndromes with the hallmark of increased risk for cranial, spinal, and peripheral schwannomas. Neurofibromatosis type 2 was recently renamed as NF2-related SWN and is the most common SWN syndrome, with increased risk for bilateral vestibular schwannomas, intradermal schwannomas, meningiomas, and less commonly, ependymoma. SMARCB1-related SWN is a familial SWN syndrome associated with peripheral and spinal schwannomas and an increased risk for meningiomas and malignant peripheral nerve sheath tumors, even in the absence of radiation. These individuals do not develop bilateral vestibular schwannomas. Finally, patients with LZTR1-related SWN typically present with peripheral schwannomas, and unilateral vestibular schwannomas have been reported. The following perspective is intended to highlight the clinical presentation and international tumor surveillance recommendations across these SWN syndromes.

Spatial mapping of immune cell environments in NF2-related schwannomatosis vestibular schwannoma

NF2-related Schwannomatosis (NF2 SWN) is a rare disease characterised by the growth of multiple nervous system neoplasms, including bilateral vestibular schwannoma (VS). VS tumours are characterised by extensive leucocyte infiltration. However, the immunological landscape in VS and the spatial determinants within the tumour microenvironment that shape the trajectory of disease are presently unknown. In this study, to elucidate the complex immunological networks across VS, we performed imaging mass cytometry (IMC) on clinically annotated VS samples from NF2 SWN patients. We reveal the heterogeneity in neoplastic cell, myeloid cell and T cell populations that co-exist within VS, and that distinct myeloid cell and Schwann cell populations reside within varied spatial contextures across characteristic Antoni A and B histomorphic niches. Interestingly, T-cell populations co-localise with tumour-associated macrophages (TAMs) in Antoni A regions, seemingly limiting their ability to interact with tumorigenic Schwann cells. This spatial landscape is altered in Antoni B regions, where T-cell populations appear to interact with PD-L1+ Schwann cells. We also demonstrate that prior bevacizumab treatment (VEGF-A antagonist) preferentially reduces alternatively activated-like TAMs, whilst enhancing CD44 expression, in bevacizumab-treated tumours. Together, we describe niche-dependent modes of T-cell regulation in NF2 SWN VS, indicating the potential for microenvironment-altering therapies for VS.

Efficacy and Toxicity of Bevacizumab in Children with NF2-Related Schwannomatosis: A Systematic Review

BACKGROUND/OBJECTIVES

NF2-related schwannomatosis (NF2) is a tumor predisposition syndrome that typically presents with bilateral vestibular schwannomas, together with other intracranial and spinal schwannomas, meningiomas, and/or ependymomas. Bevacizumab, a VEGF inhibitor, has the potential to decrease schwannoma volume and improve hearing in adults, but the literature on the effects in children is sparse. This narrative review aims to evaluate the use of bevacizumab in pediatric NF2 patients, focusing on hearing, tumor progression, and toxicity.

METHODS

A literature review was conducted following PRISMA guidelines. Articles were searched in PubMed, Embase, Web of Science, Cochrane Library, Emcare, and Academic Search Premier on 18 July 2024. Inclusion criteria were patients ≤ 18 years, diagnosed with NF2 and treated with bevacizumab. Two authors independently assessed the quality of the evidence and extracted relevant data from the included articles.

RESULTS

Seventeen articles including 62 pediatric NF2 patients met the inclusion criteria. Studies varied widely in treatment regimens and outcome parameters. Tumor regression was reported in 6/56 patients (11%) and 38/56 (68%) remained stable. Hearing improved in 15/45 patients (33%) and did not further deteriorate in 27/45 (60%). An improvement in other symptoms was seen in 6/29 patients (28%). Toxicity was reported in five studies, documenting 13 adverse events in 28 patients ranging from grade 1 to grade 3. Treatment was discontinued in both patients who experienced grade 3 toxicity.

CONCLUSIONS

Bevacizumab seems to be a viable treatment option for pediatric NF2 patients. Tumor regression or stabilization is achieved in the majority of patients (77%). Moreover, a considerable number of pediatric patients experience hearing stabilization or improvement (93%). Bevacizumab appears to be relatively well tolerated, offering a non-invasive therapeutic option for children with NF2 suffering from progressive vestibular schwannomas and hearing loss.

Neurofibromatosis type-2-related schwannomatosis presenting as peripapillary hamartoma: report on a novel NF2 mutation

BACKGROUND

Neurofibromatosis type-2-related schwannomatosis (NF2-SWN, formerly neurofibromatosis type 2) is a rare genetic disorder marked by the development of multiple nervous system tumors.

CASE PRESENTATION

We report a 21-month-old female patient who presented for left eye deviation. Upon examination, intermittent exotropia and a fundus mass were detected. Wide field fundus examination revealed the presence of a combined hamartoma involving the optic nerve and retina. This finding was supported by MRI highlighting the lesion's characteristics. The patient's father and other relatives on the paternal side displayed symptoms of NF2-SWN, evident through the presence of acoustic neuroma, although they did not exhibit any ocular symptoms. DNA analysis revealed a novel loss-of-function mutation in exon 15 of the NF2 gene (NM_000268.3: c.1627_1628del, p.Lys543Aspfs *21) in both the patient and her father at a heterozygous state. By the age of three, her vision worsened, and optical coherence tomography showed vitreomacular traction and intraretinal fluid surrounding the lesion.

CONCLUSION

This case underscores the need to consider NF2- SWN in peripapillary hamartoma diagnoses and highlights the importance of genetic testing for early detection and management.

Gene Therapy for Neurofibromatosis Type 2-Related Schwannomatosis: Recent Progress, Challenges, and Future Directions

Neurofibromatosis type 2 (NF2)-related schwannomatosis is a rare autosomal dominant monogenic disorder caused by mutations in the NF2 gene. The hallmarks of NF2-related schwannomatosis are bilateral vestibular schwannomas (VS). The current treatment options for NF2-related schwannomatosis, such as observation with serial imaging, surgery, radiotherapy, and pharmacotherapies, have shown limited effectiveness and serious complications. Therefore, there is a critical demand for novel effective treatments. Gene therapy, which has made significant advancements in treating genetic diseases, holds promise for the treatment of this disease. This review covers the genetic pathogenesis of NF2-related schwannomatosis, the latest progress in gene therapy strategies, current challenges, and future directions of gene therapy for NF2-related schwannomatosis.

Long-term outcomes of stereotactic radiosurgery for intracranial schwannoma in neurofibromatosis type 2: a genetic analysis perspective

PURPOSE

Neurofibromatosis type 2 (NF2) is intractable because of multiple tumors involving the nervous system and is clinically diverse and genotype-dependent. Stereotactic radiosurgery (SRS) for NF2-associated schwannomas remains controversial. We aimed to investigate the association between radiosurgical outcomes and mutation types in NF2-associated schwannomas.

METHODS

This single-institute retrospective study included consecutive NF2 patients with intracranial schwannomas treated with SRS. The patients' types of germline mutations ("Truncating," "Large deletion," "Splice site," "Missense," and "Mosaic") and Halliday's genetic severity scores were examined, and the associations with progression-free rate (PFR) and overall survival (OS) were analyzed.

RESULTS

The study enrolled 14 patients with NF2 with 22 associated intracranial schwannomas (median follow-up, 102 months).　The PFRs in the entire cohort were 95% at 5 years and 90% at 10-20 years. The PFRs tended to be worse in patients with truncating mutation exons 2-13 than in those with other mutation types (91% at 5 years and 82% at 10-20 years vs. 100% at 10-20 years, P = 0.140). The OSs were 89% for patients aged 40 years and 74% for those aged 60 years in the entire cohort and significantly lower in genetic severity group 3 than in the other groups (100% vs. 50% for those aged 35 years; P = 0.016).

CONCLUSION

SRS achieved excellent PFR for NF2-associated intracranial schwannomas in the mild (group 2A) and moderate (group 2B) groups. SRS necessitates careful consideration for the severe group (group 3), especially in cases with NF2 truncating mutation exons 2-13.

Extensive, 3.8 Mb-Sized Deletion of 22q12 in a Patient with Bilateral Schwannoma, Intellectual Disability, Sensorineural Hearing Loss, and Epilepsy

Introduction

In contrast with the well-known and described deletion of the 22q11 chromosome region responsible for DiGeorge syndrome, 22q12 deletions are much rarer. Only a few dozen cases have been reported so far. This region contains genes responsible for cell cycle control, chromatin modification, transmembrane signaling, cell adhesion, and neural development, as well as several cancer predisposition genes.

Case Presentation

We present a patient with cleft palate, sensorineural hearing loss, vestibular dysfunction, epilepsy, mild to moderate intellectual disability, divergent strabism, pes equinovarus, platyspondylia, and bilateral schwannoma. Using Microarray-based Comparative Genomic Hybridization (aCGH), we identified the de novo 3.8 Mb interstitial deletion at 22q12.1→22q12.3. We confirmed deletion of the critical NF2 region by MLPA analysis.

Discussion

Large 22q12 deletion in the proband encases the critical NF2 region, responsible for development of bilateral schwannoma. We compared the phenotype of the patient with previously reported cases. Interestingly, our patient developed cleft palate even without deletion of the MN1 gene, deemed responsible in previous studies. We also strongly suspect the DEPDC5 gene deletion to be responsible for seizures, consistent with previously reported cases.

Correlation between genotype and phenotype with special attention to hearing in 14 Japanese cases of NF2-related schwannomatosis

NF2-related schwannomatosis (NF2) is an autosomal dominant genetic disorder caused by variants in the NF2 gene. Approximately 50% of NF2 patients inherit pathogenic variants, and the remainder acquire de novo variants. NF2 is characterized by development of bilateral vestibular schwannomas. The genetic background of Japanese NF2 cases has not been fully investigated, and the present report performed a genetic analysis of 14 Japanese NF2 cases and examined genotype-phenotype correlations. DNA samples collected from peripheral blood were analyzed by next-generation sequencing, multiplex ligation-dependent probe amplification analysis, and in vitro electrophoresis. Ten cases had pathogenic or likely pathogenic variants in the NF2 gene, with seven truncating variants and three non-truncating variants. The age of onset in all seven cases with truncating variants was < 20 years. The age of onset significantly differed among cases with truncating NF2 variants, non-truncating NF2 variants, and no NF2 variants. However, the clinical course of tumor growth and hearing deterioration were not predicted only by germline pathogenic NF2 variants. The rate of truncating variants was higher in the present study than that of previous reports. Genotype-phenotype correlations in the age of onset were present in the analyzed Japanese NF2 cases.

Loss of social independence in patients with neurofibromatosis type 2: a follow-up study using a national registry in Japan

BACKGROUND

For patients with neurofibromatosis type 2 (NF2), maintaining an independent state of living is important. The present study aimed to examine the loss of social independence (i.e., a status that patients can work and go to school) and its contributing factors in patients with NF2 using data from a national registry in Japan.

METHODS

This longitudinal study used a registry database containing information on patients with NF2 who had submitted initial claims to receive medical expense subsidies between 2004 and 2010. Patients with "employed," "studying," and "housekeeping" categories were classified as "socially independent." Patients who were socially independent at baseline were followed-up for up to nine years. The primary outcome of the present study was the loss of social independence during the follow-up period, which was defined as the change in status from being socially independent to socially dependent. First, we examined longitudinal associations between demographic variables and neurological symptoms at baseline and the loss of social independence. Second, we examined whether the occurrence of neurological symptoms is associated with a loss of social independence in patients.

RESULTS

A total of 156 patients were included in the present study. During the follow-up period, 37 (23.7%) patients experienced a loss of social independence. In the first analysis, the multivariate logistic regression model showed that the loss of social independence was significantly more frequent among patients with spinal dysfunction than among patients without. In the second analysis, logistic regression analyses showed that neurological symptoms, including bilateral hearing loss, facial nerve palsy, cerebellar dysfunction, decreased facial sensation, speech dysfunction (dysphagia/dysarthria and aphasia), double vision, blindness, hemiparesis, and seizures, were significantly associated with loss of social independence.

CONCLUSIONS

The occurrence of various neurological symptoms of NF2 can hinder social independence in the long term. Medical service providers need to observe patients while considering the risks, and provide appropriate support to address neurological symptoms that can restrict social independence, as this will lead to maintaining social engagement.

Antisense oligonucleotides targeting exon 11 are able to partially rescue the NF2-related schwannomatosis phenotype in vitro

NF2-related schwannomatosis (NF2-related SWN) is an autosomal dominant condition caused by loss of function variants in the NF2 gene, which codes for the protein Merlin and is characterized by the development of multiple tumors of the nervous system. The clinical presentation of the disease is variable and related to the type of the inherited germline variant. Here, we tested if phosphorodiamidate morpholino oligomers (PMOs) could be used to correct the splice signaling caused by variants at ±13 within the intron-exon boundary region and showed that the PMOs designed for these variants do not constitute a therapeutic approach. Furthermore, we evaluated the use of PMOs to decrease the severity of the effects of NF2 truncating variants with the aim of generating milder hypomorphic isoforms in vitro through the induction of the in-frame deletion of the exon-carrying variant. We were able to specifically induce the skipping of exons 4, 8, and 11 maintaining the NF2 gene reading frame at cDNA level. Only the skipping of exon 11 produced a hypomorphic Merlin (Merlin-e11), which is able to partially rescue the observed phenotype in primary fibroblast cultures from NF2-related SWN patients, being encouraging for the treatment of patients harboring truncating variants located in exon 11.

Vestibular schwannoma associated with neurofibromatosis type 2: Clinical course following stereotactic radiosurgery

Objective

A lack of understanding of the clinical course of neurofibromatosis type 2 (NF2)-associated vestibular schwannoma (VS) often complicates the decision-making in terms of optimal timing and mode of treatment. We investigated the outcomes of stereotactic radiosurgery (SRS) in this population.

Methods

We retrospectively analyzed NF2 patients treated with Gamma-Knife SRS for VS in our tertiary referral center. A total of 41 treated lesions from 33 patients were collected with a follow-up period of 69.1 (45.0-104.8) months. We reviewed the treatment history, hearing function, and other treatment-related morbidities in individual cases. We also analyzed pre- and post-treatment tumor volumes via imaging studies. Longitudinal volumetric analyses were conducted for the tumor volume response of the 41 treated lesions following SRS. The growth pattern of 22 unirradiated lesions during an observation period of 83.4 (61.1-120.4) months was separately evaluated.

Results

Most treated lesions showed effective tumor control up to 85% at 60 months after SRS, whereas unirradiated lesions progressed with a relative volume increase of 14.0% (7.8-27.0) per year during the observation period. Twelve (29%) cases showed pseudoprogression with significant volume expansion in the early follow-up period, which practically reduced the rate of tumor control to 57% at 24 months. Among the patients with serviceable hearing, two (20%) cases lost the hearing function on the treated side during the early follow-up period within 24 months.

Conclusions

Progressive NF2-associated VS can be adequately controlled by SRS but the short-term effects of this treatment are not highly advantageous in terms of preserving hearing function. SRS treatment candidates should therefore be carefully selected.

Primary Benign Tumors of the Spinal Canal

Benign tumors that grow in the spinal canal are heterogeneous neoplasms with low incidence; from these, meningiomas and nerve sheath tumors (neurofibromas and schwannomas) account for 60%-70% of all primary spinal tumors. Benign spinal canal tumors provoke nonspecific clinical manifestations, mostly related to the affected level of the spinal cord. These tumors present a challenge for the patient and healthcare professionals, for they are often difficult to diagnose and the high frequency of posttreatment complications. In this review, we describe the epidemiology, risk factors, clinical features, diagnosis, histopathology, molecular biology, and treatment of extramedullary benign meningiomas, osteoid osteomas, osteoblastomas, aneurysmal bone cysts, osteochondromas, neurofibromas, giant cell tumors of the bone, eosinophilic granulomas, hemangiomas, lipomas, and schwannomas located in the spine, as well as possible future targets that could lead to an improvement in their management.

Management of neurofibromatosis type 2 and schwannomatosis associated peripheral and intraspinal schwannomas: influence of surgery, genetics, and localization

Introduction

Peripheral and intraspinal schwannomas are common and clinically complex pathologies in patients with Neurofibromatosis Type 2 (NF2) and Schwannomatosis (SWNT). Functional preservation and pain relief are the major goals in treating these tumors.

Methods

This retrospective observational study investigates the clinical and functional outcome of 205 operated peripheral (n = 148, 72%) and intraspinal (n = 57, 28%) schwannomas in 85 patients (53 NF2, 32 SWNT) treated at our department between 2006 and 2017. Associated factors such as genetics, age, and location were evaluated.

Results

Persisting drug-resistant pain was the most common symptom (84%, n = 173) and indication for surgery (54%, n = 110). Improvement in pain intensity was postoperatively seen in 81%. Peripheral nerve schwannomas exhibited worse pain intensity preoperatively compared to intraspinal lesions (p = 0.017 NF2, p = 0.029 SWNT). More total resections could be achieved in 93% of SWNT vs. 82% of NF2-associated tumors, p = 0.030). NF2 patients with intraspinal lesions were more neurologically affected (p < 0.05). Perioperative comparison of both tumor syndromes showed more neurological deficits (p = 0.027), and less pain (p = 0.024) in NF2-associated tumors. Mosaic NF2 patients had worse pain levels before surgery, and SWNT patients had a worse neurological function and more pain compared to non-mosaic or non-mutated cases.

Conclusions

Resection of peripheral and intraspinal schwannomas is an effective and low-risk treatment in both NF2 and SWNT. Patients with severe pain have a particular benefit from surgical treatment. Intraspinal lesions are associated with worse neurological function whereas peripheral lesions showed a higher pain intensity. The influence of mutations needs to be further investigated in larger cohorts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-022-04061-0.

Early prediction of functional prognosis in neurofibromatosis type 2 patients based on genotype-phenotype correlation with targeted deep sequencing

Regardless of treatment, the clinical progression of neurofibromatosis type 2 (NF2), particularly in terms of hearing, swallowing, and gait, tend to worsen throughout the patients' lives. We performed a retrospective analysis of functional outcomes in Japanese NF2 patients to predict their functional prognosis. We analyzed genotype-phenotype correlation based on genetic data from a cohort of 57 patients with a mean follow-up of 14.5 ± 6.0 years. Their functional outcomes, including hearing, swallowing, and ambulation, were reviewed. Performing a targeted deep sequencing, germline NF2 mutations were identified in 28 patients (49.1%), and mosaic NF2 was identified in 20 patients (20, 35.0%). The functional preservation period and outcome differed significantly depending on clinical/genetic factors. Among these factors, "Truncating", "Mosaic", and "Age of symptom onset ≥ 25" had the most significant effects on functional disability. By applying a combination of an NF2 mutation type/location, and age of symptom onset, we classified different degrees of functional preservation and progression, schwannoma growth rate and total interventions per year per patient. The prediction of detailed functional outcomes in NF2 patients can plan better strategies for life-long disease management and social integration.

Stereotactic radiosurgery for vestibular schwannomas in neurofibromatosis type 2 patients: a systematic review and meta-analysis

INTRODUCTION

Neurofibromatosis type 2 (NF2) is characterized by often bilateral vestibular schwannomas (VS) that result in progressive hearing loss and compression of nearby brainstem structures causing cranial nerve palsies. Treatment of these tumors remains challenging, as both surgical removal and expectant management can result in symptom progression. Stereotactic radiosurgery (SRS) has been investigated for the management of NF2-associated VS; however, the role, promises, and pitfalls of this treatment modality remain unclear.

METHODS

Ovid MEDLINE, EMBASE, Web of Science, and Cochrane Reviews were searched for studies assessing SRS outcome in NF2-associated VS only. Primary endpoints included tumor control, serviceable hearing, presence of tinnitus, and cranial nerve V and VII symptoms.

RESULTS

A total of 16 studies (589 patients harboring 750 tumors) were analyzed. Clinical tumor control was achieved in 88% of cases (95% CI 80-95%); salvage surgery was needed in 8% (95% CI 4-13%) of cases. Treatment resulted in a worsening of pre-treatment serviceable hearing (OR = 0.26, p < 0.01), increased facial nerve (OR = 1.62, p < 0.01) and trigeminal nerve (OR = 1.42, p = 0.07) impairment. The incidence of vestibular symptoms and hydrocephalus were not consistently reported and thus could not be assessed.

CONCLUSIONS

The treatment of NF2-associated VS continues to pose a challenge, as current SRS regimens result in impaired hearing and worse cranial nerve comorbidities, despite achieving high tumor control. It remains unclear if these findings have to be regarded as treatment complications or, rather, continued disease progression.

Origins of biallelic inactivation of NF2 in Neurofibromatosis Type 2

BACKGROUND

Elucidating the mechanism by which biallelic inactivation evolved could provide a mechanistic understanding for NF2 tumorigenesis and also a rationale for clinical management.

METHODS

A cohort of 60 NF2 patients was recruited. Next-generation sequencing of tumor and paired control samples was used to explore how NF2 mutations evolve in determining the clinical phenotypes.

RESULTS

Total 60 blood samples (one from each patient) and 61 (from 35 patients) NF2 associated tumors were collected. Next-generation sequencing of the blood samples detected "first hit" NF2 mutation in 35/60 donors (58.3%), 82.9% of which (29/35) bear heterozygous germline mutations, and 17.1% (6/35) of which are mosaics with variable allelic frequency (VAF). Whilst a number of NF2 patients were found without germline mutation, most (57/61, 93.4%) NF2 associated tumors were identified with NF2 somatic mutation. We calculated the correlation between the onset latency of mosaic and germline NF2 allele carriers with the mosaicism VAF. The mosaicism VAF is negatively and linearly correlated to clinical symptom onset latency (R2 0.3677, P=0.00351), suggesting biallelic inactivation probability is a linear function of 'first hit' prevalence in the body. The second NF2 somatic mutation occurrence time positively correlates with the onset of clinical symptom (R2=0.4151, P=0.02633), suggesting tumor growth is linearly proportional to the time after biallelic inactivation.

CONCLUSIONS

Our results suggested that biallelic inactivation of NF2 evolved through neutral drift and pre-existing first hit NF2 allele determines certain aspects of the clinical symptom. Genetic diagnosis should be included in the diagnostic criteria and treatment consideration of NF2.

Pathogenic noncoding variants in the neurofibromatosis and schwannomatosis predisposition genes

Neurofibromatosis type 1 (NF1), type 2 (NF2), and schwannomatosis are a group of autosomal dominant disorders that predispose to the development of nerve sheath tumors. Pathogenic variants (PVs) that cause NF1 and NF2 are located in the NF1 and NF2 loci, respectively. To date, most variants associated with schwannomatosis have been identified in the SMARCB1 and LZTR1 genes, and a missense variant in the DGCR8 gene was recently reported to predispose to schwannomas. In spite of the high detection rate for PVs in NF1 and NF2 (over 90% of non-mosaic germline variants can be identified by routine genetic screening) underlying PVs for a proportion of clinical cases remain undetected. A higher proportion of non-NF2 schwannomatosis cases have no detected PV, with PVs currently only identified in around 70%-86% of familial cases and 30%-40% of non-NF2 sporadic schwannomatosis cases. A number of variants of uncertain significance have been observed for each disorder, many of them located in noncoding, regulatory, or intergenic regions. Here we summarize noncoding variants in this group of genes and discuss their established or potential role in the pathogenesis of NF1, NF2, and schwannomatosis.

Age at Onset and Presenting Symptoms of Neurofibromatosis Type 2 as Prognostic Factors for Clinical Course of Vestibular Schwannomas

The presenting symptoms of the tumor suppressor gene syndrome neurofibromatosis type 2 (NF2) are often non-specific and unrelated to the disease hallmark bilateral vestibular schwannomas (VS). However, age at onset and presenting symptoms may have predictive values for the clinical course of VS. In this retrospective single-center study, we addressed this issue by reviewing 106 patients with 194 VS. Presenting symptoms attributable to VS commonly occur in 87% of adults and 31% of children. Age at onset significantly correlates with tumor volumes at presentation (p = 0.034). In addition, age at onset significantly correlates with pure-tone average (p = 0.0001), speech discrimination scores (p = 0.001), age at beginning of hearing loss (p = 0.0001), age at deafness (p = 0.0001), and age at first surgery (p = 0.0001). Patients presenting with VS related symptoms had significantly (p < 0.05) worse hearing values at presentation and after surgery. These patients also exhibited higher growth rates and tumor volumes compared to patients with non-VS related presenting symptoms, but this difference did not reach the significance level of p < 0.05. Due to the late appearance of these symptoms, the time of beginning hearing loss, surgery and deafness is significantly delayed (p < 0.05) compared to patients not presenting with VS. In summary, age at onset and type of presenting symptom provide excellent prognostic parameters for predicting VS- and hearing-related clinical course.

Managing NF2-associated vestibular schwannomas in children and young adults: review of an institutional series regarding effects of surgery and bevacizumab on growth rates, tumor volume, and hearing quality

We reviewed our experience in managing of NF2-associated vestibular schwannoma (VS) in children and young adults regarding the effect of surgery and postoperative bevacizumab treatment. A total of 579 volumetric and hearing data sets were analyzed. The effect of surgery on tumor volume and growth rate was investigated in 46 tumors and on hearing function in 39 tumors. Long-term hearing follow-up behavior was compared with 20 non-operated ears in additional 15 patients. Sixteen operated VS were treated with bevacizumab. Mutation analysis of the NF2 gene was performed in 25 patients. Surgery significantly slowed down VS growth rate. Factors associated with a higher growth rate were increasing patient age, tumor volume, and constitutional truncating mutations. Immediately after surgery, functional hearing was maintained in 82% of ears. Deterioration of hearing was associated with initial hearing quality, larger tumor volumes, and larger resection amounts. Average hearing scores were initially better in the group of non-operated VS. Over time, hearing scores in both groups worsened with a similar dynamic. During bevacizumab treatment of residual tumors, four different patterns of growth were observed. Decompression of the internal auditory canal with various degrees of tumor resection decreases the postoperative tumor growth rates. Carefully tailored BAEP-guided surgery does not cause additional hearing deterioration. Secondary bevacizumab treatment showed heterogenous effects both regarding tumor size and hearing preservation. It seems that postoperative tumor residuals, that grow slower, behave differently to bevacizumab than reported for not-operated faster growing VS.

Management of NF2-associated vestibular schwannomas in children and young adults: influence of surgery and clinical factors on tumor volume and growth rate

OBJECTIVE

The authors' aim was to evaluate the tumor volume and growth rate of neurofibromatosis type 2 (NF2)-associated vestibular schwannomas (VSs) and the clinical factors or type of mutations before and after surgery in children and adults younger than 25 years at the time of diagnosis.

METHODS

A total of 579 volumetric measurements were performed in 46 operated tumors in 28 NF2 patients, using thin-slice (< 3 mm) T1-weighted contrast-enhanced MRI. The follow-up period ranged from 21 to 167 months (mean 75 months). Growth rate was calculated using a multilinear regression model. Mutation analysis of the NF2 gene was performed in 25 patients.

RESULTS

Surgery significantly (p = 0.013) slowed the VS growth rate from 0.69 ± 1.30 cm3/yr to 0.23 ± 0.42 cm3/yr. Factors significantly associated with a higher growth rate of VSs were increasing patient age (p < 0.0005), tumor volume (p = 0.006), tumor size (p = 0.001), and constitutional truncating mutations in the NF2 gene (p = 0.018). VS growth rates tended to be higher in patients with spinal ependymomas and in right-sided tumors and lower in the presence of peripheral schwannomas; however, no statistical significance was achieved.

CONCLUSIONS

Decompression of the internal auditory canal with various degrees of tumor resection decreases the postoperative tumor growth rate in children and young adults with NF2-associated VS. Patients with potential risk factors for accelerated growth (e.g., large volume, truncating mutations) and with increasing age should be monitored more closely before and after surgery.

Trends in phenotype in the English paediatric neurofibromatosis type 2 cohort stratified by genetic severity

Childhood onset neurofibromatosis type 2 can be severe and genotype dependent. We present a retrospective phenotypic analysis of all ascertained children in England 1.0). Focal cortical dysplasia occurred in 26% group 3 and 4% 2A. A total of 48% of group 3 underwent ≥1 major intervention (intracranial/spinal surgery/Bevacizumab/radiotherapy) compared to 35% of 2A; with 23% group 3 undergoing spinal surgery (schwannoma/ependymoma/meningioma resection) compared to 4% of 2A. Mean age starting Bevacizumab was 12.7 in group 3 and 14.9 years in 2A. In conclusion, group 3 phenotype manifests earlier with greater tumour load, poorer visual outcomes and more intervention.

Peripheral nervous system alterations in infant and adult neurofibromatosis type 2

OBJECTIVE

To examine the involvement of dorsal root ganglia and peripheral nerves in children with neurofibromatosis type 2 compared to healthy controls and symptomatic adults by in vivo high-resolution magnetic resonance neurography.

METHODS

In this prospective multicenter study, the lumbosacral dorsal root ganglia and sciatic, tibial, and peroneal nerves were examined in 9 polyneuropathy-negative children diagnosed with neurofibromatosis type 2 by a standardized magnetic resonance neurography protocol at 3T. Volumes of dorsal root ganglia L3 to S2 and peripheral nerve lesions were assessed and compared to those of 29 healthy children. Moreover, dorsal root ganglia volumes and peripheral nerve lesions were compared to those of 14 adults with neurofibromatosis type 2.

RESULTS

Compared to healthy controls, dorsal root ganglia hypertrophy was a consistent finding in children with neurofibromatosis type 2 (L3 +255%, L4 +289%, L5 +250%, S1 +257%, and S2 +218%, p < 0.001) with an excellent diagnostic accuracy. Moreover, peripheral nerve lesions occurred with a high frequency in those children compared to healthy controls (18.89 ± 11.11 vs 0.90 ± 1.08, p < 0.001). Children and adults with neurofibromatosis type 2 showed nonsignificant differences in relative dorsal root ganglia hypertrophy rates (p = 0.85) and peripheral nerve lesions (p = 0.28).

CONCLUSIONS

Alterations of peripheral nerve segments occur early in the course of neurofibromatosis type 2 and are evident even in children not clinically affected by peripheral polyneuropathy. While those early alterations show similar characteristics compared to adults with neurofibromatosis type 2, the findings of this study suggest that secondary processes might be responsible for the development and severity of associated polyneuropathy.

Stereotactic body radiotherapy for benign spinal tumors: Meningiomas, schwannomas, and neurofibromas

Stereotactic body radiation therapy (SBRT) is a relatively new technology, and its use among patients with benign spinal tumors has limited prospective data. Similar to intracranial benign tumors treated successfully with SBRT, benign spinal tumors of the same histology can also develop, and SBRT may be an effective treatment alternative in inoperable or recurrent cases. Outcomes in patients with neurofibromatosis type 1, neurofibromatosis type 2, or schwannomatosis treated with SBRT have also been reported. Single institution reports have shown local control rates over 90% and improvement in clinical symptoms. The optimum dose and fractionation to maximize local control and minimize toxicity is unknown, with few incidences of radiation treatment-related toxicities. Given the location and benign nature of these tumors, careful management of dose to critical organs is essential. With continued follow-up, the optimum use of SBRT in patients with benign spinal tumors can be better defined.

Towards Molecular Classification of Meningioma: Evolving Treatment and Diagnostic Paradigms

Meningioma, a common primary brain tumor in adults, is graded based on World Health Organization criteria that rely on histology alone. This approach is unable to determine conclusively which tumors, especially benign or atypical, will recur. Molecular characterization of meningioma has identified genetic biomarkers that can predict tumor behavior. Only a few genetic changes are known to classify >85% of all meningioma and clinical trials using targeted therapy to genetic subtypes of meningioma are under way. Immunotherapy is also being trialed in treating high-grade and recurrent meningioma. This review summarizes recent developments characterizing meningioma using genetic and immunologic biomarkers and how these molecular tools may be integrated into existing care together with current World Health Organization grading to improve diagnosis, prognosis, and therapy.

Cancer and Central Nervous System Tumor Surveillance in Pediatric Neurofibromatosis 2 and Related Disorders

The neurofibromatoses consist of at least three autosomal-dominant inherited disorders: neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis. For over 80 years, these conditions were inextricably tied together under generalized neurofibromatosis. In 1987, the localization of NF1 to chromosome 17q and NF2 (bilateral vestibular schwannoma) to 22q led to a consensus conference at Bethesda, Maryland. The two main neurofibromatoses, NF1 and NF2, were formally separated. More recently, the SMARCB1 and LZTR1 genes on 22q have been confirmed as causing a subset of schwannomatosis. The last 26 years have seen a great improvement in understanding of the clinical and molecular features of these conditions as well as insights into management. Childhood presentation of NF2 (often with meningioma) in particular predicts a severe multitumor disease course. Malignancy is rare in NF2, particularly in childhood; however, there are substantial risks from benign and low-grade central nervous system (CNS) tumors necessitating MRI surveillance to optimize management. At least annual brain MRI, including high-resolution images through the auditory meatus, and a clinical examination and auditory assessment are required from diagnosis or from around 10 to 12 years of age if asymptomatic. Spinal imaging at baseline and every 2 to 3 years is advised with more frequent imaging if warranted on the basis of sites of tumor involvement. The malignancy risk in schwannomatosis is not well defined but may include an increased risk of malignant peripheral nerve sheath tumor in SMARCB1 Imaging protocols are also proposed for SMARCB1 and LZTR1 schwannomatosis and SMARCE1-related meningioma predisposition. Clin Cancer Res; 23(12); e54-e61. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Childhood neurofibromatosis type 2 (NF2) and related disorders: from bench to bedside and biologically targeted therapies

Neurofibromatosis type 2 [NF2; MIM # 101000] is an autosomal dominant disorder characterised by the occurrence of vestibular schwannomas (VSs), schwannomas of other cranial, spinal and cutaneous nerves, cranial and spinal meningiomas and/or other central nervous system (CNS) tumours (e.g., ependymomas, astrocytomas). Additional features include early onset cataracts, optic nerve sheath meningiomas, retinal hamartomas, dermal schwannomas (i.e., NF2-plaques), and (few) café-au-lait spots. Clinically, NF2 children fall into two main groups: (1) congenital NF2 - with bilateral VSs detected as early as the first days to months of life, which can be stable/asymptomatic for one-two decades and suddenly progress; and (2) severe pre-pubertal (Wishart type) NF2- with multiple (and rapidly progressive) CNS tumours other-than-VS, which usually present first, years before VSs [vs. the classical adult (Gardner type) NF2, with bilateral VSs presenting in young adulthood, sometimes as the only disease feature]. Some individuals can develop unilateral VS associated with ipsilateral meningiomas or multiple schwannomas localised to one part of the peripheral nervous system [i.e., mosaic NF2] or multiple non-VS, non-intradermal cranial, spinal and peripheral schwannomas (histologically proven) [schwannomatosis]. NF2 is caused by mutations in the NF2 gene at chromosome 22q12.1, which encodes for a protein called merlin or schwannomin, most similar to the exrin-readixin-moesin (ERM) proteins; mosaicNF2 is due to mosaic phenomena for the NF2 gene, whilst schwannomatosis is caused by coupled germ-line and mosaic mutations either in the SMARCB1 gene [SWNTS1; MIM # 162091] or the LZTR1 gene [SWNTS2; MIM # 615670] both falling within the 22q region and the NF2 gene. Data driven from in vitro and animal studies on the merlin pathway [e.g., post-translational and upstream/downstream regulation] allowed biologically targeted treatment strategies [e.g., Lapatinib, Erlotinib, Bevacizumab] aimed to multiple tumour shrinkage and/or regression and tumour arrest of progression with functional improvement.

Genetic Severity Score predicts clinical phenotype in NF2

​BACKGROUND: The clinical severity of disease in neurofibromatosis type 2 (NF2) is variable. Patients affected with a constitutional truncating NF2 mutation have severe disease, while missense mutations or mosaic mutations present with a milder attenuated phenotype. Genotype-derived natural history data are important to inform discussions on prognosis and management.

METHODS

We have assessed NF2 clinical phenotype in 142 patients in relation to the UK NF2 Genetic Severity Score to validate its use as a clinical and research tool.

RESULTS

The Genetic Severity Score showed significant correlations across 10 measures, including mean age at diagnosis, proportion of patients with bilateral vestibular schwannomas, presence of intracranial meningioma, spinal meningioma and spinal schwannoma, NF2 eye features, hearing grade, age at first radiotherapy, age at first surgery and age starting bevacizumab. In addition there was moderate but significant correlation with age at loss of useful hearing, and weak but significant correlations for mean age at death, quality of life, last optimum Speech Discrimination Score and total number of major interventions. Patients with severe disease presented at a younger age had a higher disease burden and greater requirement of intervention than patients with mild and moderate disease.

CONCLUSIONS

This study validates the UK NF2 Genetic Severity Score to stratify patients with NF2 for both clinical use and natural history studies.

First evidence of genotype-phenotype correlations in Gorlin syndrome

BACKGROUND

Gorlin syndrome (GS) is an autosomal dominant syndrome characterised by multiple basal cell carcinomas (BCCs) and an increased risk of jaw cysts and early childhood medulloblastoma. Heterozygous germline variants in PTCH1 and SUFU encoding components of the Sonic hedgehog pathway explain the majority of cases. Here, we aimed to delineate genotype-phenotype correlations in GS.

METHODS

We assessed genetic and phenotypic data for 182 individuals meeting the diagnostic criteria for GS (median age: 47.1; IQR: 31.1-61.1). A total of 126 patients had a heterozygous pathogenic variant, 9 had SUFU pathogenic variants and 46 had no identified mutation.

RESULTS

Patients with variants were more likely to be diagnosed earlier (p=0.02), have jaw cysts (p=0.002) and have bifid ribs (p=0.003) or any skeletal abnormality (p=0.003) than patients with no identified mutation. Patients with a missense variant in PTCH1 were diagnosed later (p=0.03) and were less likely to develop at least 10 BCCs and jaw cysts than those with other pathogenic PTCH1 variants (p=0.03). Patients with SUFU pathogenic variants were significantly more likely than those with PTCH1 pathogenic variants to develop a medulloblastoma (p=0.009), a meningioma (p=0.02) or an ovarian fibroma (p=0.015), but were less likely to develop a jaw cyst (p=0.0004).

CONCLUSION

We propose that the clinical heterogeneity of GS can in part be explained by the underlying or SUFU variant.

The response of spinal cord ependymomas to bevacizumab in patients with neurofibromatosis Type 2

OBJECTIVE

People with neurofibromatosis Type 2 (NF2) have a genetic predisposition to nervous system tumors. NF2-associated schwannomas stabilize or decrease in size in over half of the patients while they are receiving bevacizumab. NF2 patients treated with bevacizumab for rapidly growing schwannoma were retrospectively reviewed with regard to ependymoma prevalence and response to treatment.

METHODS

The records of 95 NF2 patients receiving bevacizumab were retrospectively reviewed with regard to spinal ependymoma prevalence and behavior. The maximum longitudinal extent (MLE) of the ependymoma and associated intratumoral or juxtatumoral cysts were measured on serial images. Neurological changes and patient function were reviewed and correlated with radiological changes.

RESULTS

Forty-one of 95 patients were found to have ependymomas (median age 26 years; range 11–53 years). Thirty-two patients with a total of 71 ependymomas had scans appropriate for serial assessment with a mean follow-up of 24 months (range 3–57 months). Ependymomas without cystic components showed minimal change in MLE. Twelve patients had ependymomas with cystic components or syringes. In these patients, reductions in MLE were observed, particularly due to decreases in the cystic components of the ependymoma. Clinical improvement was seen in 7 patients, who all had cystic ependymomas.

CONCLUSIONS

Bevacizumab treatment in NF2 patients with spinal cord ependymomas results in a decrease in the size of intratumoral and juxtatumoral cysts as well as adjacent-cord syringes and a decrease in cord edema. This may provide clinical benefit in some patients, although the changes do not meet the current criteria for radiological tumor response.

Gamma Knife radiosurgery for treatment of growing vestibular schwannomas in patients with neurofibromatosis Type 2: a matched cohort study with sporadic vestibular schwannomas

OBJECTIVE Neurofibromatosis Type 2 (NF2) is a tumor syndrome characterized by an autosomal dominant pattern of inheritance. The hallmark of NF2 is the development of bilateral vestibular schwannomas (VSs), generally by 30 years of age. One of the first-line treatment options for small to medium-large VSs is radiosurgery. Although radiosurgery shows excellent results in sporadic VS, its use in NF2-related VS is still a topic of dispute. The aim of this study was to evaluate long-term tumor control, hearing preservation rates, and factors influencing outcome of optimally dosed, contemporary Gamma Knife radiosurgery (GKRS) for growing VSs in patients with NF2 and compare the findings to data obtained in patients with sporadic VS also treated by means of GKRS. METHODS The authors performed a retrospective analysis of 47 growing VSs in 34 NF2 patients who underwent GKRS treatment performed with either the Model C or Perfexion Leksell Gamma Knife, with a median margin dose of 11 Gy. Actuarial tumor control rates were estimated using the Kaplan-Meier method. For patient- and treatment-related factors, a Cox proportional hazards model was used to identify predictors of outcome. Trigeminal, facial, and vestibulocochlear nerve function were assessed before and after treatment. NF2-related VS patients were matched 1:1 with sporadic VS patients who were treated in the same institute, and the same indications for treatment, definitions, and dosimetry were used in order to compare outcomes. RESULTS Actuarial tumor control rates in NF2 patients after 1, 3, 5, and 8 years were 98%, 89%, 87%, and 87%, respectively. Phenotype and tumor volume had significant hazard rates of 0.086 and 22.99, respectively, showing that Feiling-Gardner phenotype and a tumor volume not exceeding 6 cm³ both were associated with significantly better outcome. Actuarial rates of serviceable hearing preservation after 1, 3, 5, and 7 years were 95%, 82%, 59%, and 33%, respectively. None of the patients experienced worsening of trigeminal nerve function. Facial nerve function worsened in 1 patient (2.5%). No significant differences in tumor control, hearing preservation, or complications were found in comparing the results of GKRS for NF2-related VS versus GKRS for sporadic VS. CONCLUSIONS With modern GKRS, the use of low margin doses for treating growing VSs in patients with NF2 demonstrates good long-term tumor control rates. Feiling-Gardner phenotype and tumor volume smaller than 6 cm³ seem to be independently associated with prolonged progression-free survival, highlighting the clinical importance of phenotype assessment before GKRS treatment. In addition, no significant differences in tumor control rates or complications were found in the matched-control cohort analysis comparing GKRS for VS in patients with NF2 and GKRS for sporadic VS. These results show that GKRS is a valid treatment option for NF2-related VS, in addition to being a good option for sporadic VS, particularly in patients with the Feiling-Gardner phenotype and/or tumors that are small to medium in size. Larger tumors in patients with the Wishart phenotype appear to respond poorly to radiosurgery, and other treatment modalities should therefore be considered in such cases.

Diagnosis, Management, and New Therapeutic Options in Childhood Neurofibromatosis Type 2 and Related Forms

Neurofibromatosis type 2 (NF2; MIM # 101000) is an autosomal dominant disorder characterized by the development of vestibular schwannomas (VSs); schwannomas of other cranial, spinal, and cutaneous nerves; cranial and spinal meningiomas or other central nervous system tumors (eg, ependymomas and astrocytomas) or both. Additional features include eye (eg, early onset cataracts, optic nerve sheath meningiomas, retinal or pigment epithelial hamartomas or both, and epithelial retinal membranes) and skin abnormalities (eg, flat dermal [NF2 plaques] or spherical subcutaneous nodular schwannomas or both, and few, atypical café-au-lait spots). Clinically, children with NF2 fall into 2 main groups: (1) congenital NF2 with bilateral VSs detected as early as the first days to months of life, which can be stable or asymptomatic for 1-2 decades and suddenly progress; and (2) severe prepubertal (Wishart type) NF2 with multiple (and rapidly progressive) central nervous system tumors other-than-VS, which usually presents first, years before VSs, both associated with more marked skin and eye involvement (vs the classical mild adult [Gardner type] NF2, with bilateral VSs presenting in young adulthood, sometimes as the only disease feature). Individuals manifesting unilateral VS associated with ipsilateral meningiomas or multiple schwannomas localized to a part of the peripheral nervous system have mosaic or segmental NF2; individuals developing multiple nonVS, nonintradermal cranial, spinal, and peripheral schwannomas (histologically proven) have schwannomatosis (SWNTS). NF2 is caused by mutations in the NF2 gene at chromosome 22q12.1, which encodes for a protein called merlin or schwannomin, most similar to the exrin-readixin-moesin proteins; mosaic or segmental NF2 is because of mosaic phenomena for the NF2 gene, whereas SWNTS is caused by germline and possibly mosaic mutations either in the SMARCB1 gene (SWNTS1; MIM # 162091) or the LZTR1 gene (SWNTS2; MIM # 615670), both falling within the 22q region. Data driven from in vitro and animal studies on the merlin pathway allowed biologically targeted treatment strategies (employing Lapatinib, Erlotinib, Everolimus, Picropodophyllin, OSU.03012, Imatinib, Sorafenib, and Bevacizumab) aimed at multiple tumor shrinkage or regression or both and tumor arrest of progression with functional improvement.

Mosaic and Intronic Mutations in TSC1/TSC2 Explain the Majority of TSC Patients with No Mutation Identified by Conventional Testing

Tuberous sclerosis complex (TSC) is an autosomal dominant tumor suppressor gene syndrome due to germline mutations in either TSC1 or TSC2. 10–15% of TSC individuals have no mutation identified (NMI) after thorough conventional molecular diagnostic assessment. 53 TSC subjects who were NMI were studied using next generation sequencing to search for mutations in these genes. Blood/saliva DNA including parental samples were available from all subjects, and skin tumor biopsy DNA was available from six subjects. We identified mutations in 45 of 53 subjects (85%). Mosaicism was observed in the majority (26 of 45, 58%), and intronic mutations were also unusually common, seen in 18 of 45 subjects (40%). Seventeen (38%) mutations were seen at an allele frequency < 5%, five at an allele frequency < 1%, and two were identified in skin tumor biopsies only, and were not seen at appreciable frequency in blood or saliva DNA. These findings illuminate the extent of mosaicism in TSC, indicate the importance of full gene coverage and next generation sequencing for mutation detection, show that analysis of TSC-related tumors can increase the mutation detection rate, indicate that it is not likely that a third TSC gene exists, and enable provision of genetic counseling to the substantial population of TSC individuals who are currently NMI.

Tuberous sclerosis complex (TSC) is a human genetic disorder due to mutations in the TSC1 or TSC2 genes. A mystery for many years has been the fact that with standard genetic testing 10–15% of TSC patients have had no mutation identified (NMI) in either TSC1 or TSC2. We examined the genetic cause of TSC in patients who were ‘NMI’ after previous testing. We found a mutation in TSC1 or TSC2 in the vast majority of the subjects studied: 45 of 53 (85%). The majority of mutations identified were either in introns or mosaic or both. Usually we expect to find mutations causing human disease in exons, coding parts of genes. However, mutations can also be found in introns, the non-coding parts of genes, and we found intronic mutations in 18 of 45 subjects (40%). Mosaic mutations were seen in 26 of 45 subjects (58%). Mosaicism is the situation in which different cells in the body have a different genetic make-up, and in this case the mutations in TSC1/TSC2 were present in only a fraction of the cells from the patient. So these two types of hard-to-find mutations (in introns and/or mosaic) explain the majority of TSC patients who were NMI.

Clinical and molecular predictors of mortality in neurofibromatosis 2: a UK national analysis of 1192 patients

BACKGROUND

Neurofibromatosis 2 (NF2) is an autosomal-dominant tumour predisposition syndrome characterised by bilateral vestibular schwannomas, considerable morbidity and reduced life expectancy. Although genotype-phenotype correlations are well established in NF2, little is known about effects of mutation type or location within the gene on mortality. Improvements in NF2 diagnosis and management have occurred, but their effect on patient survival is unknown.

METHODS

We evaluated clinical and molecular predictors of mortality in 1192 patients (771 with known causal mutations) identified through the UK National NF2 Registry. Kaplan-Meier survival and Cox regression analyses were used to evaluate predictors of mortality, with jackknife adjustment of parameter SEs to account for the strong intrafamilial phenotypic correlations that occur in NF2.

RESULTS

The study included 241 deaths during 10 995 patient-years of follow-up since diagnosis. Early age at diagnosis and the presence of intracranial meningiomas were associated with increased mortality, and having a mosaic, rather than non-mosaic, NF2 mutation was associated with reduced mortality. Patients with splice-site or missense mutations had lower mortality than patients with truncating mutations (OR 0.459, 95% CI 0.213 to 0.990, and OR 0.196, 95% CI 0.213 to 0.990, respectively). Patients with splice-site mutations in exons 6-15 had lower mortality than patients with splice-site mutations in exons 1-5 (OR 0.333, 95% CI 0.129 to 0.858). The mortality of patients with NF2 diagnosed in more recent decades was lower than that of patients diagnosed earlier.

CONCLUSIONS

Continuing advances in molecular diagnosis, imaging and treatment of NF2-associated tumours offer hope for even better survival in the future.

Determination of the mutant allele frequency in patients with neurofibromatosis type 2 and somatic mosaicism by means of deep sequencing

Neurofibromatosis Type 2 (NF2) is an autosomal disorder caused by mutations of the NF2 gene. More than half of all NF2 patients have unaffected parents and carry de novo mutations, which may be of prezygotic or postzygotic origin. The latter can result in mosaicism, which is relatively common in NF2 patients. Previous studies indicated that, in 50% of patients with mosaic NF2 mutations, the mutant allele is only detectable by Sanger sequencing of PCR products amplified from tumor tissue but not from blood samples. In order to establish a highly sensitive method that has the power to detect low levels of NF2 mutant alleles from blood samples of mosaic NF2 patients, we performed ultra deep sequencing and calculated the percentage of mutant and wildtype NF2 alleles. The mutant allele frequencies detected ranged from 2.6% to 19.7%. In three patients, however, the NF2 mutation previously identified in tumor tissue was not identified in blood samples by means of deep sequencing, suggesting absence of mutant cells in the blood. Remarkably, we observed a correlation between the age at onset of the disease and the mutant allele frequency. Our study indicates that ultra deep sequencing is an effective and highly sensitive method to determine the mutant allele frequency in patients with mosaic NF2 gene mutations, which enables extended phenotype/correlations in these patients. © 2015 Wiley Periodicals, Inc.

Chromosome 22q12.1 microdeletions: confirmation of the MN1 gene as a candidate gene for cleft palate

We report on seven novel patients with a submicroscopic 22q12 deletion. The common phenotype constitutes a contiguous gene deletion syndrome on chromosome 22q12.1q12.2, featuring NF2-related schwannoma of the vestibular nerve, corpus callosum agenesis and palatal defects. Combining our results with the literature, eight patients are recorded with palatal defects in association with haploinsufficiency of 22q12.1, including the MN1 gene. These observations, together with the mouse expression data and the finding of craniofacial malformations including cleft palate in a Mn1-knockout mouse model, suggest that this gene is a candidate gene for cleft palate in humans.

Neurofibromatosis type 2

Type 2 neurofibromatosis (NF2) is an autosomal dominant disorder caused by mutations in the NF2 tumor suppressor gene NF2 on chromosome 22. Around 1 in 33000 people are born with an NF2 mutation although more than one-third of the 60% of de novo cases are not conceived with the mutation but this develops later in embryogenesis (mosaics). NF2 has a substantial effect on life expectancy and individuals with a constitutional truncating mutation have the worst prognosis. The vast majority of people with NF2 will develop bilateral vestibular schwannomas with many developing schwannomas on other cranial, spinal and peripheral nerves. Cranial and spinal meningiomas and intraspinal low grade indolent ependymomas are the other major tumor features. Cutaneous features can be subtle with only 70% having evidence of intracutaneous plaque-like schwannomas or subcutaneous lesions on peripheral nerves. Café-au-lait patches are more frequent than in the general population but in only around 1% will meet NIH criteria for NF1.

NF2/merlin in hereditary neurofibromatosis 2 versus cancer: biologic mechanisms and clinical associations

Inactivating germline mutations in the tumor suppressor gene NF2 cause the hereditary syndrome neurofibromatosis 2, which is characterized by the development of neoplasms of the nervous system, most notably bilateral vestibular schwannoma. Somatic NF2 mutations have also been reported in a variety of cancers, but interestingly these mutations do not cause the same tumors that are common in hereditary neurofibromatosis 2, even though the same gene is involved and there is overlap in the site of mutations. This review highlights cancers in which somatic NF2 mutations have been found, the cell signaling pathways involving NF2/merlin, current clinical trials treating neurofibromatosis 2 patients, and preclinical findings that promise to lead to new targeted therapies for both cancers harboring NF2 mutations and neurofibromatosis 2 patients.

Long-term follow-up studies of Gamma Knife surgery for patients with neurofibromatosis Type 2

Object

The aim of this study was to evaluate long-term clinical outcomes after Gamma Knife surgery (GKS) for patients with neurofibromatosis Type 2 (NF2) and the role of GKS in the management of NF2.

Methods

From December 1994 through December 2008, a total of 46 patients (21 male, 25 female) with NF2 underwent GKS and follow-up evaluation for at least 5 years at the Gamma Knife Center of the Beijing Neurosurgical Institute. GKS was performed using the Leksell Gamma Knife Models B and C. The mean age of the patients was 30 years (range 13–59 years). A family history of NF2 was found for 9 (20%) patients. The NF2 phenotype was thought to be Wishart for 20 (44%) and Feiling-Gardner for 26 (56%) patients. Among these 46 patients, GKS was performed to treat 195 tumors (73 vestibular schwannomas and 122 other tumors including other schwannomas and meningiomas). For vestibular schwannomas, the mean volume was 5.1 cm3 (median 3.6 cm3, range 0.3–27.3 cm3), the mean margin dose was 12.9 Gy (range 10–14 Gy), and the mean maximum dose was 27.3 Gy (range 16.2–40 Gy). For other tumors, the mean volume was 1.7 cm3 (range 0.3–5.5 cm3), the mean margin dose was 13.3 Gy (range 11–14 Gy), and the mean maximum dose was 26.0 Gy (range 18.0–30.4 Gy). The median duration of follow-up was 109 months (range 8–195 months).

Results

For the 73 vestibular schwannomas that underwent GKS, the latest follow-up MR images demonstrated regression of 30 (41%) tumors, stable size for 31 (43%) tumors, and enlargement of 12 (16%) tumors. The total rate of tumor control for bilateral vestibular schwannomas in patients with NF2 was 84%. Of the 122 other types of tumors that underwent GKS, 103 (85%) showed no tumor enlargement. The rate of serviceable hearing preservation after GKS was 31.9% (15/47). The actuarial rates for hearing preservation at 3 years, 5 years, 10 years, and 15 years were 98%, 93%, 44%, and 17%, respectively. Of the 46 patients, 22 (48%) became completely bilaterally deaf, 17 (37%) retained unilateral serviceable hearing, and 7 (15%) retained bilateral serviceable hearing. The mean history of the disease course was 12 years (range 5–38 years).

Conclusions

GKS was confirmed to provide long-term local tumor control for small- to medium-sized vestibular schwannomas and other types of tumors, although vestibular schwannomas in patients with NF2 responded less well than did unilateral sporadic vestibular schwannomas. Phenotype is the most strongly predictive factor of final outcome after GKS for patients with NF2. The risk for loss of hearing is high, whereas the risk for other cranial nerve complications is low.

Novel age-dependent targets in vestibular schwannomas

Background

Schwannomas are the most common neurofibromatosis type 2 (NF2)-associated tumors with significant phenotypic heterogeneity in patients. The most severe subtype has an early and rapid progression and the mild type has a later onset and a less aggressive course. The aim of this study was to elucidate the underlying molecular differences between these groups. We compared the gene expression pattern between patients with early to late age of onset.

Results

A gene signature of 21 genes was constructed to differentiate between early-onset and late-onset patients. We confirmed these results by real-time PCR for SNF1LK2, NGFRAP1L1 (BEX 5), GMNN, and EPHA2.

Conclusion

Genes identified here may be additional aberrations in merlin-depleted cells that govern the disease onset. A significant number of these genes have been suggested as having a role in carcinogenesis and are used as biomarkers for prognosis in several other cancers. The role of these genes in NF2 carcinogenesis and their potential as biomarkers or drug target are worthwhile exploring.

Longitudinal evaluation of quality of life in 288 patients with neurofibromatosis 2

Advances in molecular biology have resulted in novel therapy for neurofibromatosis 2-related (NF2) tumours, highlighting the need for robust outcome measures. The disease-focused NF2 impact on quality of life (NFTI-QOL) patient questionnaire was assessed as an outcome measure for treatment in a multi-centre study. NFTI-QOL was related to clinician-rated severity (ClinSev) and genetic severity (GenSev) over repeated visits. Data were evaluated for 288 NF2 patients (n = 464 visits) attending the English national NF2 clinics from 2010 to 2012. The male-to-female ratio was equal and the mean age was 42.2 (SD 17.8) years. The analysis included NFTI-QOL eight-item score, ClinSev graded as mild, moderate, or severe, and GenSev as a rank order of the number of NF2 mutations (graded as mild, moderate, severe). The mean (SD) 8.7 (5.4) score for NFTI-QOL for either a first visit or all visits 9.2 (5.4) was similar to the published norm of 9.4 (5.5), with no significant relationships with age or gender. NFTI-QOL internal reliability was good, with a Cronbach’s alpha score of 0.85 and test re-test reliability r = 0.84. NFTI related to ClinSev (r = 0.41, p < 0.001; r = 0.46 for all visits), but weakly to GenSev (r = 0.16, p < 0.05; r = 0.15 for all visits). ClinSev related to GenSev (r = 0.41, p < 0.001; r = 0.42 for all visits). NFTI-QOL showed a good reliability and ability to detect significant longitudinal changes in the QOL of individuals. The moderate relationships of NFTI-QOL with clinician- and genetic-rated severity suggest that NFTI-QOL taps into NF2 patient experiences that are not encompassed by ClinSev rating or genotype.

Clinicopathologic assay of 15 tumor resections in a family with neurofibromatosis type 2

The objective of this study is the management of multiple family members with multiple neurofibromatosis type 2 (NF2) related tumors of the skull base that can be challenging, on purely technical, decision-making, and ethical levels. These issues are addressed in this manuscript based on an experience treating an unique large family with NF2. A retrospective chart review was performed, reviewing clinical, radiological, surgical, and pathological data. A unique family of 17 siblings, whose father was the proband as a sporadic mutation is reported. Over a 4-month period, five of eight affected siblings underwent 12 procedures for resection of 15 different NF2-related tumors. This single family experience of NF2-related skull base tumors underscores the importance of preservation of function and quality of life as the major determinants of treatment success.

Neurofibromatosis type 2 (NF2): diagnosis and management

Neurofibromatosis type 2 (NF2) is an autosomal dominant inherited tumor predisposition syndrome caused by mutations in the NF2 gene on chromosome 22. Affected individuals develop schwannomas typically involving both vestibular nerves leading to hearing loss and eventual deafness. Rehabilitation with brainstem implants and in some cases cochlear implants is improving this outcome. Schwannomas also occur on other cranial nerves, on spinal nerve roots and peripheral nerves, and intracutaneously as plaques. Cranial and spinal meningiomas and spinal ependymomas are other common tumors. Fifty to sixty percent of patients represent de novo mutations and as many as 33% of these are mosaic for the underlying disease causing mutation. Truncating mutations (nonsense, frameshift insertions/deletions) are the most frequent germline events and cause the most severe disease, whilst single and multiple exon deletions are common and are usually associated with milder NF2. Neurological deficits are a major feature of the condition and neurologists have a pivotal role in assigning symptoms to lesions and in managing neuropathies. NF2 represents a difficult management problem with most patients facing substantial morbidity and reduced life expectancy. Surgery remains the focus of current management although watchful waiting and occasionally radiation treatment have a role. We are seeing the advent of tailored drug therapies aimed at the genetic level and these are likely to provide huge improvements for this devastating, life-limiting condition.