Plexiform neurofibromas in children with neurofibromatosis type 1: frequency and associated clinical deficits

Contemporary Approach to Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors

Most malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive high-grade sarcomas, arising in individuals with neurofibromatosis type 1 (NF1) at a significantly elevated estimated lifetime frequency of 8%-13%. In the setting of NF1, MPNSTs arise from malignant transformation of benign plexiform neurofibroma and borderline atypical neurofibromas. Composed of neoplastic cells from the Schwannian lineage, these cancers recur in approximately 50% of individuals, and most patients die within five years of diagnosis, despite surgical resection, radiation, and chemotherapy. Treatment for metastatic disease is limited to cytotoxic chemotherapy and investigational clinical trials. In this article, we review the pathophysiology of this aggressive cancer and current approaches to surveillance and treatment.

Association of plexiform and diffuse neurofibromas with malignant peripheral nerve sheath tumor in NF I patients: a whole-body MRI assessment

OBJECTIVE

The aim of this study is to evaluate neurofibromatosis type 1 (NF1) patients with whole-body MRI (WBMRI) to investigate the frequency of plexiform neurofibromas (pNFs), diffuse neurofibromas (dNFs), and malignant peripheral nerve sheath tumors (MPNSTs).

MATERIALS AND METHODS

In this retrospective cross-sectional study, between the years 2015 and 2023, 83 consecutive patients with known NF1 underwent a total of 110 WBMRI screenings for MPNST using a standardized institutional protocol. The lesions are categorized as discrete lesions, pNFs, dNFs, and MPNSTs. Histopathology served as the reference standard for all MPNSTs.

RESULTS

Among the 83 patients analyzed, 53 (64%) were women and 30 were men (36%) of ages 36.94±14.43 years (range, 15-66 years). Of the 83 patients, 33 have a positive family history of NF1 and positive genetic studies. Seven of 83 (8%) have only dNF, 20/83 (24%) have pNF, 28/83 (34%) have both dNF and pNF, and 28/83 (34%) have neither. Of the 83 patients, eight (9.6%) were diagnosed with nine total MPNSTs. Age range for patients with MPNSTs at time of diagnosis was 22-51, with an average age of 33.4 years. Only one MPNST (11%) developed from underlying pNF 4 years after WBMRI along the right bronchial tree. Three of eight (37.5%) patients with MPNST died within 5 years of pathologic diagnosis.

CONCLUSION

This study suggests the absence of a predisposition for development of MPNST from pNFs and dNFs in the setting of NF1. As such, these lesions may not need special surveillance compared to discrete peripheral nerve sheath tumors.

The PlexiQoL, a patient-reported outcome measure on quality of life in neurofibromatosis type 1-associated plexiform neurofibroma: translation, cultural adaptation and validation into the Dutch language for the Netherlands

BACKGROUND

Half of the patients with Neurofibromatosis type 1 (NF1) develop one or more tumours called plexiform neurofibromas, which can have a significant impact on Quality of Life (QoL). The PlexiQoL questionnaire is a disease-specific QoL measure for adults with NF1-associated plexiform neurofibromas. The aim of this study was to adapt and validate a Dutch version of the PlexiQoL for the Netherlands.

METHODS

The PlexiQoL was translated using the dual-panel methodology, followed by cognitive debriefing interviews to assess face and content validity. The psychometric properties were evaluated by administering the questionnaire on two separate occasions to a sample of adults with NF1 and plexiform neurofibromas. Feasibility was evaluated by the presence of floor/ceiling effects. Reliability was assessed by evaluating Cronbach's alpha coefficient and test-retest reliability, using Spearman's rank correlation coefficients. Mann-Whitney U tests were used to check for known group validity. The Nottingham Health Profile (NHP) questionnaire was used as comparator questionnaire to evaluate convergent validity.

RESULTS

The translation and cognitive debriefing interviews resulted in a Dutch version of the PlexiQoL that reflected the original concept and underlying semantic meanings of the UK English version. Forty participants completed the validation survey. The Dutch PlexiQoL demonstrated excellent internal consistency (Cronbach's α 0.825) and test-retest reliability (Spearman correlation coefficient 0.928). The questionnaire detected differences in PlexiQoL scores between participants based on self-reported general health and disease severity. Convergent validity was confirmed for relevant NHP subsections.

CONCLUSIONS

The Dutch PlexiQoL demonstrated excellent psychometric properties and can be reliably used to measure plexiform neurofibroma-related QoL in adults with NF1 in the Netherlands.

Cancer Predisposition Syndromes in Neuro-oncology

Although most primary central and peripheral nervous system (NS) tumors occur sporadically, there are a subset that may arise in the context of a cancer predisposition syndrome. These syndromes occur due to a pathogenic mutation in a gene that normally functions as a tumor suppressor. With increased understanding of the molecular pathogenesis of these tumors, more people have been identified with a cancer predisposition syndrome. Identification is crucial, as this informs surveillance, diagnosis, and treatment options. Moreover, relatives can also be identified through genetic testing. Although there are many cancer predisposition syndromes that increase the risk of NS tumors, in this review, we focus on three of the most common cancer predisposition syndromes, neurofibromatosis type 1, neurofibromatosis type 2, and tuberous sclerosis complex type 1 and type 2, emphasizing the clinical manifestations, surveillance guidelines, and treatment options.

Heterozygous NF1 dermal fibroblasts modulate exosomal content to promote angiogenesis in a tissue-engineered skin model of neurofibromatosis type-1

Neovascularization is a critical process in tumor progression and malignant transformation associated with neurofibromatosis type 1 (NF1). Indeed, fibroblasts are known to play a key role in the tumoral microenvironment modification by producing an abundant collagenous matrix, but their contribution in paracrine communication pathways is poorly understood. Here, we hypothesized that NF1 heterozygosis in human dermal fibroblasts could promote angiogenesis through exosomes secretion. The purposes of this study are to identify the NF1 fibroblast-derived exosome protein contents and to determine their proangiogenic activity. Angiogenic proteome measurement confirmed the overexpression of VEGF and other proteins involved in vascularization. Tube formation of microvascular endothelial cells was also enhanced in presence of exosomes derived from NF1 skin fibroblasts. NF1 tissue-engineered skin (NF1-TES) generation showed a significantly denser microvessels networks compared to healthy controls. The reduction of exosomes production with an inhibitor treatment demonstrated a drastic decrease in blood vessel formation within the dermis. Our results suggest that NF1 haploinsufficiency alters the dermal fibroblast function and creates a pro-angiogenic signal via exosomes, which increases the capillary formation. This study highlights the potential of targeting exosome secretion and angiogenesis for therapeutic interventions in NF1.

Long-term safety and efficacy of selumetinib in children with neurofibromatosis type 1 on a phase 1/2 trial for inoperable plexiform neurofibromas

BACKGROUND

Selumetinib shrank inoperable symptomatic plexiform neurofibromas (PN) in children with neurofibromatosis type 1 (NF1) and provided clinical benefit for many in our previously published phase 1/2 clinical trials (SPRINT, NCT01362803). At the data cutoff (DCO) of the prior publications, 65% of participants were still receiving treatment. This report presents up to 5 years of additional safety and efficacy data from these studies.

METHODS

This manuscript includes data from the phase 1 and phase 2, stratum 1 study which included participants with clinically significant PN-related morbidity. Participants received continuous selumetinib dosing (1 cycle = 28 days). Safety and efficacy data through February 27, 2021 are included. PN response assessed by volumetric magnetic resonance imaging analysis: Confirmed partial response (cPR) ≥20% decrease from baseline on 2 consecutive evaluations. Phase 2 participants completed patient-reported outcome measures assessing tumor pain intensity (Numeric Rating Scale-11) and interference of pain in daily life (pain interference index).

RESULTS

For the 74 children (median age 10.3 years; range 3-18.5) enrolled, overall cPR rate was 70% (52/74); median duration of treatment was 57.5 cycles (range 1-100). Responses were generally sustained with 59% (44) lasting ≥ 12 cycles. Tumor pain intensity (n = 19, P = .015) and pain interference (n = 18, P = .0059) showed durable improvement from baseline to 48 cycles. No new safety signals were identified; however, some developed known selumetinib-related adverse events (AEs) for the first time after several years of treatment.

CONCLUSIONS

With up to 5 years of additional selumetinib treatment, most children with NF1-related PN had durable tumor shrinkage and sustained improvement in pain beyond that previously reported at 1 year. No new safety signals were identified; however, ongoing monitoring for known selumetinib-related AEs is needed while treatment continues.

Audiometric and Otologic Findings in Children and Young Adults with Neurofibromatosis Type 1 and Plexiform Neurofibromas

OBJECTIVES

To characterize otologic and audiologic manifestations in our NF1 cohort and explore the relationship between otologic and audiologic findings in a subset of patients with ear-related plexiform neurofibromas (PNs).

METHODS

Audiologic and otologic clinical evaluations were conducted on 102 patients with NF1 in a natural history study (5-45 years; M = 14.4 years; Mdn = 14). Testing included pure tone and speech audiometry, middle ear function, neurodiagnostic auditory brainstem response (ABR), auditory processing, and MRIs of the head and neck region. Patients referred to this study had an overall higher incidence and burden of PNs than the overall NF1 population.

RESULTS

The majority of subjects in this cohort had normal hearing sensitivity (81%) and normal middle ear function (78%). Nineteen participants had hearing loss that ranged in degree from mild to profound, with the majority in the mild range. Hearing loss was twice as likely to be conductive than sensorineural. In patients with ear-related PNs (n = 12), hearing loss was predominantly conductive (60%). Seventy-five percent of ears with PNs had atypical tympanometric tracings that could not be characterized by the classic categories. In all 20 patients with a PN in the temporal bone, the ear canal was affected, and the PNs often extended to the surrounding soft tissue regions.

CONCLUSIONS

People with NF1-related PNs in the temporal bone and adjacent skull base should have audiometric and otologic monitoring. Addressing hearing concerns should be part of routine clinical evaluations in patients with NF1. Magnetic resonance imaging (MRI) should be performed in patients with NF1 who have hearing loss.

LEVEL OF EVIDENCE

3 Laryngoscope, 133:2770-2778, 2023.

Plexiform neurofibromatosis of the lower back: A rare case report

INTRODUCTION

Plexiform neurofibromatosis is a relatively rare manifestation of Type 1 neurofibromatosis (NF-1). This condition leads to gross disfiguration along with functional disability. We are presenting a case of 49 year male with Plexiform neurofibromatosis of lower back. The aim of this rare case report is also to discuss the management difficulties encountered.

PRESENTATION OF CASE

A 49 year male presented to us with gradually increasing swelling over the lower back which was present since his 10 years of age. He had already undergone debulking surgery for the same swelling 10 years back. For the last 2 years the swelling had increased in significant amount. He gave history of similar swellings in his father and grandfather. Proper examination revealed multiple café au lait macules, giant plexiform neurofibroma over lower back and multiple nodular swellings all over the body (neuroma). Biopsy report from previous surgery showed neurofibroma. He underwent debulking surgery. The procedure went for 12 h continuous. Intraoperatively, the mass was highly vascular and excessive bleeding was encountered. About 3 L of blood loss was there and patient received 12 units of blood products.

DISCUSSION

Plexiform neurofibromas are uncommon and may occur in around 30 % patients with NF-1. The genetic defect lies in chromosome 17 that encodes a protein neurofibromin. It causes disfiguration and severe distress to patients. Debulking surgery is one of the treatments to decrease the difficulties occurred from the mass. The aim of this report is to discuss the difficulties occurred in surgical intervention of this rare condition like excessive blood loss.

CONCLUSION

Although timely intervention could limit the disfigurement and morbidity associated with large lesion, due to unpredictable natural course and growth pattern, it is difficult to decide best time to intervene surgically. Registration of such rare case facilitates patient monitoring and development of appropriate treatment protocols.

Treatment decisions and the use of MEK inhibitors for children with neurofibromatosis type 1-related plexiform neurofibromas

Neurofibromatosis type 1 (NF1), the most common tumor predisposition syndrome, occurs when NF1 gene variants result in loss of neurofibromin, a negative regulator of RAS activity. Plexiform neurofibromas (PN) are peripheral nerve sheath tumors that develop in patients with NF1 and are associated with substantial morbidity and for which, until recently, the only treatment was surgical resection. However, surgery carries several risks and a proportion of PN are considered inoperable. Understanding the genetic underpinnings of PN led to the investigation of targeted therapies as medical treatment options, and the MEK1/2 inhibitor selumetinib has shown promising efficacy in pediatric patients with NF1 and symptomatic, inoperable PN. In a phase I/II trial, most children (approximately 70%) achieved reduction in tumor volume accompanied by improvements in patient-reported outcomes (decreased tumor-related pain and improvements in quality of life, strength, and range of motion). Selumetinib is currently the only licensed medical therapy indicated for use in pediatric patients with symptomatic, inoperable NF1-PN, with approval based on the results of this pivotal clinical study. Several other MEK inhibitors (binimetinib, mirdametinib, trametinib) and the tyrosine kinase inhibitor cabozantinib are also being investigated as medical therapies for NF1-PN. Careful consideration of multiple aspects of both disease and treatments is vital to reduce morbidity and improve outcomes in patients with this complex and heterogeneous disease, and clinicians should be fully aware of the risks and benefits of available treatments. There is no single treatment pathway for patients with NF1-PN; surgery, watchful waiting, and/or medical treatment are options. Treatment should be individualized based on recommendations from a multidisciplinary team, considering the size and location of PN, effects on adjacent tissues, and patient and family preferences. This review outlines the treatment strategies currently available for patients with NF1-PN and the evidence supporting the use of MEK inhibitors, and discusses key considerations in clinical decision-making.

Kinase Inhibitors in Genetic Diseases

Over the years, several studies have shown that kinase-regulated signaling pathways are involved in the development of rare genetic diseases. The study of the mechanisms underlying the onset of these diseases has opened a possible way for the development of targeted therapies using particular kinase inhibitors. Some of these are currently used to treat other diseases, such as cancer. This review aims to describe the possibilities of using kinase inhibitors in genetic pathologies such as tuberous sclerosis, RASopathies, and ciliopathies, describing the various pathways involved and the possible targets already identified or currently under study.

Clinical Characteristics and Management of Children and Adults with Neurofibromatosis Type 1 and Plexiform Neurofibromas in Denmark: A Nationwide Study

INTRODUCTION

Plexiform neurofibromas (PN) are benign nerve sheath tumours that are a frequent and potentially debilitating complication in patients with neurofibromatosis type 1 (NF1). The objective of this study was to describe the natural history of PN in children, adolescents and adults with NF1.

METHODS

This was a nationwide, longitudinal cohort study of patients with NF1 under observation at the two national centres of NF1 expertise in Denmark between 2000 and 2020. Patient and clinical characteristics were documented from individual medical records.

RESULTS

A total of 1099 patients with NF1 were included. Overall, 12% (35/296) of paediatric patients and 21% (172/803) of adult patients had ≥ 1 large PN (≥ 3 cm). Approximately half of patients with a large PN had ≥ 1 symptomatic PN. The most frequent symptoms were pain, neurological deficits, cosmetic issues, disfigurement, compression, increased psychosocial burden and vision loss. Clinical evaluations of PN size were available for 40 PN in 34 paediatric patients and 191 PN in 159 adult patients with large PN. Surgery (complete resection or debulking) was performed in 38% (15/40) of PN in paediatric patients and 45% (86/191) in adult patients. In addition, 35% of PN in paediatric patients and 33% in adult patients were inoperable. In a subgroup analysis, the overall PN size increased 1.06-fold per year. Malignant peripheral nerve sheath tumours (MPNST) were diagnosed in 21 patients (two paediatric and 19 adult patients).

CONCLUSIONS

This study shows that PN are common, their size and prevalence increase with age, many are often inoperable and pain and other symptoms are frequently associated. The results highlight the severe sequelae and unmet need for alternatives to analgesia and surgery in patients with PN.

Malignant Peripheral Nerve Sheath Tumors: Latest Concepts in Disease Pathogenesis and Clinical Management

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma with limited therapeutic options and a poor prognosis. Although neurofibromatosis type 1 (NF1) and radiation exposure have been identified as risk factors for MPNST, the genetic and molecular mechanisms underlying MPNST pathogenesis have only lately been roughly elucidated. Plexiform neurofibroma (PN) and atypical neurofibromatous neoplasm of unknown biological potential (ANNUBP) are novel concepts of MPNST precancerous lesions, which revealed sequential mutations in MPNST development. This review summarized the current understanding of MPNST and the latest consensus from its diagnosis to treatment, with highlights on molecular biomarkers and targeted therapies. Additionally, we discussed the current challenges and prospects for MPNST management.

ERN GENTURIS tumour surveillance guidelines for individuals with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a multisystem genetic disorder, predisposing development of benign and malignant tumours. Given the oncogenic potential, long-term surveillance is important in patients with NF1. Proposals for NF1 care and its specific manifestations have been developed, but lack integration within routine care. This guideline aims to assimilate available information on NF1 associated tumours (based on evidence and/or expert opinion) to assist healthcare professionals in undertaking tumour surveillance of NF1 individuals.

METHODS

By comprehensive literature review, performed March 18th 2020, guidelines were developed by a NF1 expert group and patient representatives, conversant with clinical care of the wide NF1 disease spectrum. We used a modified Delphi procedure to overcome issues of variability in recommendations for specific (national) health care settings, and to deal with recommendations based on indirect (scarce) evidence.

FINDINGS

We defined proposals for personalised and targeted tumour management in NF1, ensuring appropriate care for those in need, whilst reducing unnecessary intervention. We also incorporated the tumour-related psychosocial and quality of life impact of NF1.

INTERPRETATION

The guideline reflects the current care for NF1 in Europe. They are not meant to be prescriptive and may be adjusted to local available resources at the treating centre, both within and outside EU countries.

FUNDING

This guideline has been supported by the European Reference Network on Genetic Tumour Risk Syndromes (ERN GENTURIS). ERN GENTURIS is funded by the European Union. DGE is supported by the Manchester NIHRBiomedical Research Centre (IS-BRC-1215-20007).

MEK inhibitors for neurofibromatosis type 1 manifestations: Clinical evidence and consensus

The wide variety of clinical manifestations of the genetic syndrome neurofibromatosis type 1 (NF1) are driven by overactivation of the RAS pathway. Mitogen-activated protein kinase kinase inhibitors (MEKi) block downstream targets of RAS. The recent regulatory approvals of the MEKi selumetinib for inoperable symptomatic plexiform neurofibromas in children with NF1 have made it the first medical therapy approved for this indication in the United States, the European Union, and elsewhere. Several recently published and ongoing clinical trials have demonstrated that MEKi may have potential benefits for a variety of other NF1 manifestations, and there is broad interest in the field regarding the appropriate clinical use of these agents. In this review, we present the current evidence regarding the use of existing MEKi for a variety of NF1-related manifestations, including tumor (neurofibromas, malignant peripheral nerve sheath tumors, low-grade glioma, and juvenile myelomonocytic leukemia) and non-tumor (bone, pain, and neurocognitive) manifestations. We discuss the potential utility of MEKi in related genetic conditions characterized by overactivation of the RAS pathway (RASopathies). In addition, we review practical treatment considerations for the use of MEKi as well as provide consensus recommendations regarding their clinical use from a panel of experts.

Management of neurofibromatosis type 1-associated plexiform neurofibromas

Plexiform Neurofibromas (PN) are a common manifestation of the genetic disorder neurofibromatosis type 1 (NF1). These benign nerve sheath tumors often cause significant morbidity, with treatment options limited historically to surgery. There have been tremendous advances over the past two decades in our understanding of PN, and the recent regulatory approvals of the MEK inhibitor selumetinib are reshaping the landscape for PN management. At present, there is no agreed upon PN definition, diagnostic evaluation, surveillance strategy, or clear indications for when to initiate treatment and selection of treatment modality. In this review, we address these questions via consensus recommendations from a panel of multidisciplinary NF1 experts.

Whole-body MRI in children: state of the art

Whole-body magnetic resonance imaging (WBMRI) is an increasingly popular technique in paediatric imaging. It provides high-resolution anatomical information, with the potential for further exciting developments in acquisition of functional data with advanced MR sequences and hybrid imaging with radionuclide tracers. WBMRI demonstrates the extent of disease in a range of multisystem conditions and, in some cases, disease burden prior to the onset of clinical features. The current applications of WBMRI in children are hereby reviewed, along with suggested anatomical stations and sequence protocols for acquisition.

Nervous system (NS) Tumors in Cancer Predisposition Syndromes

Genetic syndromes which develop one or more nervous system (NS) tumors as one of the manifestations can be grouped under the umbrella term of NS tumor predisposition syndromes. Understanding the underlying pathological pathways at the molecular level has led us to many radical discoveries, in understanding the mechanisms of tumorigenesis, tumor progression, interactions with the tumor microenvironment, and development of targeted therapies. Currently, at least 7-10% of all pediatric cancers are now recognized to occur in the setting of genetic predisposition to cancer or cancer predisposition syndromes. Specifically, the cancer predisposition rate in pediatric patients with NS tumors has been reported to be as high as 15%, though it can approach 50% in certain tumor types (i.e., choroid plexus carcinoma associated with Li Fraumeni Syndrome). Cancer predisposition syndromes are caused by pathogenic variation in genes that primarily function as tumor suppressors and proto-oncogenes. These variants are found in the germline or constitutional DNA. Mosaicism, however, can affect only certain tissues, resulting in varied manifestations. Increased understanding of the genetic underpinnings of cancer predisposition syndromes and the ability of clinical laboratories to offer molecular genetic testing allows for improvement in the identification of these patients. The identification of a cancer predisposition syndrome in a CNS tumor patient allows for changes to medical management to be made, including the initiation of cancer surveillance protocols. Finally, the identification of at-risk biologic relatives becomes feasible through cascade (genetic) testing. These fundamental discoveries have also broadened the horizon of novel therapeutic possibilities and have helped to be better predictors of prognosis and survival. The treatment paradigm of specific NS tumors may also vary based on the patient's cancer predisposition syndrome and may be used to guide therapy (i.e., immune checkpoint inhibitors in constitutional mismatch repair deficiency [CMMRD] predisposition syndrome) [8]. Early diagnosis of these cancer predisposition syndromes is therefore critical, in both unaffected and affected patients. Genetic counselors are uniquely trained master's level healthcare providers with a focus on the identification of hereditary disorders, including hereditary cancer, or cancer predisposition syndromes. Genetic counseling, defined as "the process of helping people understand and adapt to the medical, psychological and familial implications of genetic contributions to disease" plays a vital role in the adaptation to a genetic diagnosis and the overall management of these diseases. Cancer predisposition syndromes that increase risks for NS tumor development in childhood include classic neurocutaneous disorders like neurofibromatosis type 1 and type 2 (NF1, NF2) and tuberous sclerosis complex (TSC) type 1 and 2 (TSC1, TSC2). Li Fraumeni Syndrome, Constitutional Mismatch Repair Deficiency, Gorlin syndrome (Nevoid Basal Cell Carcinoma), Rhabdoid Tumor Predisposition syndrome, and Von Hippel-Lindau disease. Ataxia Telangiectasia will also be discussed given the profound neurological manifestations of this syndrome. In addition, there are other cancer predisposition syndromes like Cowden/PTEN Hamartoma Tumor Syndrome, DICER1 syndrome, among many others which also increase the risk of NS neoplasia and are briefly described. Herein, we discuss the NS tumor spectrum seen in the abovementioned cancer predisposition syndromes as with their respective germline genetic abnormalities and recommended surveillance guidelines when applicable. We conclude with a discussion of the importance and rationale for genetic counseling in these patients and their families.

Efficacy and Safety of Trametinib in Neurofibromatosis Type 1-Associated Plexiform Neurofibroma and Low-Grade Glioma: A Systematic Review and Meta-Analysis

Trametinib has been used in neurofibromatosis type 1 (NF1) patients, especially those with unresectable nerve tumors, but no systematic review based on the latest studies has been published. We conducted this meta-analysis to evaluate the effectiveness and safety of trametinib in treating NF1-related nerve tumors. Original articles reporting the efficacy and safety of trametinib in NF1 patents were identified in PubMed, EMBASE, and Web of Science up to 1 June 2022. Using R software and the ‘meta’ package, the objective response rates (ORRs) and disease control rates (DCRs) were calculated to evaluate the efficacy, and the pooled proportion of adverse events (AEs) was calculated. The Grading of Recommendations, Assessment, Development and Evaluation system was used to assess the quality of evidence. Eight studies involving 92 patients were included, which had a very low to moderate quality of evidence. The pooled ORR was 45.3% (95% CI: 28.9–62.1%, I² = 0%), and the DCR was 99.8% (95% CI: 95.5–100%, I² = 0%). The most common AEs was paronychia, with a pooled rate of 60.7% (95% CI: 48.8–72.7%, I² = 0%). Our results indicate the satisfactory ability to stabilize tumor progression but a more limited ability to shrink tumors of trametinib in NF1-related nerve tumors. The safety profile of trametinib is satisfactory.

Epidemiological profile and clinical characteristics of 491 Brazilian patients with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a chronic and progressive autosomal dominant genetic and sporadic disease characterized by cutaneous and neurological abnormalities. Plexiform neurofibroma (PN), a significant cause of clinical complications in NF-1, is a benign tumor of the peripheral nerve sheath that involves multiple nerve fascicles. Although there is an important number of patients who are affected by NF1 in Brazil, there is little data on the behavior of the disease in the national literature as well as in other low- and middle-income countries.

METHODS

We performed a retrospective analysis of 491 patients with NF1 followed at two reference centers in Brazil.

RESULTS

Approximately 38% of patients had PNs, resulting in reduced life quality. The median patient age with PNs was 30 years (range: 6 to 83 years). Head and neck, and extremity were the main affected locations with 35.8 and 30.6%, respectively. PNs were classified as asymptomatic in 25.1% of patients, while 52.5% presented symptomatic and inoperable tumors. The most common manifestations related to PNs were disfigurement and orthopedic involvement. Twenty patients developed neoplasms and ten (50%) presented with malignant peripheral nerve sheath tumors (MPNST). The prevalence of MPNST in our study was 2.9%.

CONCLUSIONS

Patients with NF1 experience clinically significant morbidity, especially when it is associated with PN. Though there are many patients affected by NF1 in Brazil and other low- and middle-income countries, there is little data available in the corresponding literature. Our results are comparable to the previous results reported from higher-income countries and international registries.

Verbal learning and memory in youth with neurofibromatosis type 1 and plexiform neurofibromas: Relationships with disease severity

AIM

To provide a comprehensive characterization of verbal learning and memory (VLM) abilities in youth with neurofibromatosis type 1 (NF1) and plexiform neurofibromas (PNs) and to evaluate disease severity as a predictor of VLM functioning over time.

METHOD

As part of a longitudinal natural history study, youth with NF1 and PNs were administered repeat neuropsychological assessments, including measures of VLM and ratings of NF1 disease severity completed by a medical professional. This sub-study analyzed data from 89 patients (M age baseline = 13.1, SD = 4.3 years, range 6-24 years) who had completed tests of VLM abilities and verbal attention at either baseline and/or 36 months.

RESULTS

VLM scores across the sample fell predominantly within the average range of functioning at both time points. However, relative to peers with mild NF1 disease severity, youth with moderate/severe NF1 disease showed lower functioning across multiple VLM domains at 36 months, even after controlling for the effects of verbal attention.

INTERPRETATION

Exclusive use of overall domain scores does not fully characterize VLM functioning in youth with NF1 and PNs. Additionally, children and adolescents with more severe NF1 disease should be monitored more closely for verbal memory challenges and targeted for interventions.

Sleep-disordered breathing in pediatric neurofibromatosis type 1

The relationship between neurofibromatosis type 1 (NF1) and sleep-disordered breathing (SDB) has not been widely studied. The aim of the study was to analyze SDB in children with NF1 of the respiratory system. All children with NF1 followed between September 2008 and July 2020 who had a respiratory polygraphy (RP) were included. The clinical charts, cerebral and cervical magnetic resonance imaging (MRI), and RP were analyzed. Twenty-two patients (11 girls, median age at RP 8.3 [0.2-18.2] years) were included in the study. Nine patients (41%) had a NF1 involvement of the upper airways, 13 (59%) patients of the central nervous system (CNS), the cranial nerves (CN) and/or medulla, and 17 (77%) patients had a hypertrophy of the adenoids and/or tonsils. Five patients were treated with Continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV) before their first evaluation because of severe obstructive sleep apnea (OSA). Accordingly, 10 (45%) patients had no OSA, one (5%) mild OSA, 2 (9%) moderate OSA, and nine (41%) severe OSA. None of the patients had central sleep apnea. Despite upper airway surgery, three patients required CPAP, two could be weaned and one died after a switch to tracheostomy. None of the patients treated with CPAP/NIV could be weaned, one patient required tracheostomy. Neither the clinical nor the MRI findings were able to predict OSA on a RP. The prevalence of OSA in NF1 is high, regardless of the nature of airway obstruction and the clinical and MRI findings, underlining the value of a systematic RP. CPAP may reduce the need of tracheostomy.

RAS and beyond: the many faces of the neurofibromatosis type 1 protein

Neurofibromatosis type 1 is a rare neurogenetic syndrome, characterized by pigmentary abnormalities, learning and social deficits, and a predisposition for benign and malignant tumor formation caused by germline mutations in the NF1 gene. With the cloning of the NF1 gene and the recognition that the encoded protein, neurofibromin, largely functions as a negative regulator of RAS activity, attention has mainly focused on RAS and canonical RAS effector pathway signaling relevant to disease pathogenesis and treatment. However, as neurofibromin is a large cytoplasmic protein the RAS regulatory domain of which occupies only 10% of its entire coding sequence, both canonical and non-canonical RAS pathway modulation, as well as the existence of potential non-RAS functions, are becoming apparent. In this Special article, we discuss our current understanding of neurofibromin function.

Treatment of Plexiform Neurofibromas with MEK Inhibitors: First Results with a New Therapeutic Option

Neurofibromatosis type-1 (NF1)-associated plexiform neurofibromas (PN) are peripheral nerve sheath tumors that can significantly affect the quality of life. Until recently, surgery was the only treatment for these tumors. However, in most cases, surgery cannot achieve complete tumor removal and carries a high risk of postoperative deficits. Therefore, the recent approval of the MEK inhibitor selumetinib for the treatment of NF1-associated PN provides a long-awaited novel therapeutic option. Here, we report our experience with MEK inhibitor treatment in 12 pediatric NF1 patients with inoperable symptomatic PN. Eight patients received trametinib (median therapy duration 12.13 months and range 4-29 months), and four patients received selumetinib (median therapy duration 6.25 months and range 4-11 months). Volumetric magnetic resonance imaging (MRI) after 6 months of treatment was available for seven trametinib patients (median tumor volume reduction of 26.5% and range 11.3-55.7%) and two selumetinib patients (21.3% tumor volume reduction in one patient and +3% tumor volume change in the other one). All patients reported clinical benefits such as improved range of motion or reduced disfigurement. Therapy-related adverse events occurred in 58.3% of patients and mainly consisted of skin toxicity, paronychia, and gastrointestinal symptoms. Two patients discontinued trametinib treatment after 14 and 29 months when severe skin toxicity occurred and no further reduction of tumor size was observed. In one patient, discontinuation of therapy resulted in a 27.2% tumor volume increase as demonstrated on volumetric MRI 6 months later. Our data show that MEK inhibition is a novel therapeutic approach for inoperable PN with promising results and a manageable safety profile.

The Lipid Asset Is Unbalanced in Peripheral Nerve Sheath Tumors

Peripheral nerve sheath tumors (PNSTs) include schwannomas, neurofibromas (NFs), and plexiform neurofibromas (PNFs), among others. While they are benign tumors, according to their biological behavior, some have the potential for malignant degeneration, mainly PNFs. The specific factors contributing to the more aggressive behavior of some PNSTs compared to others are not precisely known. Considering that lipid homeostasis plays a crucial role in fibrotic/inflammatory processes and in several cancers, we hypothesized that the lipid asset was also unbalanced in this group of nerve tumors. Through untargeted lipidomics, NFs presented a significant increase in ceramide, phosphatidylcholine, and Vitamin A ester. PNFs displayed a marked decrease in 34 out of 50 lipid class analyzed. An increased level of ether- and oxidized-triacylglycerols was observed; phosphatidylcholines were reduced. After sphingolipidomic analysis, we observed six sphingolipid classes. Ceramide and dihydroceramides were statistically increased in NFs. All the glycosylated species appeared reduced in NFs, but increased in PNFs. Our findings suggested that different subtypes of PNSTs presented a specific modulation in the lipidic profile. The untargeted and targeted lipidomic approaches, which were not applied until now, contribute to better clarifying bioactive lipid roles in PNS natural history to highlight disease molecular features and pathogenesis.

Challenges in the diagnosis of neurofibromatosis type 1 (NF1) in young children facilitated by means of revised diagnostic criteria including genetic testing for pathogenic NF1 gene variants

Neurofibromatosis type 1 (NF1) is the most frequent disorder associated with multiple café-au-lait macules (CALM) which may either be present at birth or appear during the first year of life. Other NF1-associated features such as skin-fold freckling and Lisch nodules occur later during childhood whereas dermal neurofibromas are rare in young children and usually only arise during early adulthood. The NIH clinical diagnostic criteria for NF1, established in 1988, include the most common NF1-associated features. Since many of these features are age-dependent, arriving at a definitive diagnosis of NF1 by employing these criteria may not be possible in infancy if CALM are the only clinical feature evident. Indeed, approximately 46% of patients who are diagnosed with NF1 later in life do not meet the NIH diagnostic criteria by the age of 1 year. Further, the 1988 diagnostic criteria for NF1 are not specific enough to distinguish NF1 from other related disorders such as Legius syndrome. In this review, we outline the challenges faced in diagnosing NF1 in young children, and evaluate the utility of the recently revised (2021) diagnostic criteria for NF1, which include the presence of pathogenic variants in the NF1 gene and choroidal anomalies, for achieving an early and accurate diagnosis.

Targeted Therapies for the Neurofibromatoses

Over the past several years, management of the tumors associated with the neurofibromatoses has been recognized to often require approaches that are distinct from their spontaneous counterparts. Focus has shifted to therapy aimed at minimizing symptoms given the risks of persistent, multiple tumors and new tumor growth. In this review, we will highlight the translation of preclinical data to therapeutic trials for patients with neurofibromatosis, particularly neurofibromatosis type 1 and neurofibromatosis type 2. Successful inhibition of MEK for patients with neurofibromatosis type 1 and progressive optic pathway gliomas or plexiform neurofibromas has been a significant advancement in patient care. Similar success for the malignant NF1 tumors, such as high-grade gliomas and malignant peripheral nerve sheath tumors, has not yet been achieved; nor has significant progress been made for patients with either neurofibromatosis type 2 or schwannomatosis, although efforts are ongoing.

Impacts of NF1 Gene Mutations and Genetic Modifiers in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a tumor predisposition genetic disorder that directly affects more than 1 in 3,000 individuals worldwide. It results from mutations of the NF1 gene and shows almost complete penetrance. NF1 patients show high phenotypic variabilities, including cafe-au-lait macules, freckling, or other neoplastic or non-neoplastic features. Understanding the underlying mechanisms of the diversities of clinical symptoms might contribute to the development of personalized healthcare for NF1 patients. Currently, studies have shown that the different types of mutations in the NF1 gene might correlate with this phenomenon. In addition, genetic modifiers are responsible for the different clinical features. In this review, we summarize different genetic mutations of the NF1 gene and related genetic modifiers. More importantly, we focus on the genotype–phenotype correlation. This review suggests a novel aspect to explain the underlying mechanisms of phenotypic heterogeneity of NF1 and provides suggestions for possible novel therapeutic targets to prevent or delay the onset and development of different manifestations of NF1.

Characteristics, treatment patterns, healthcare resource use, and costs among pediatric patients diagnosed with neurofibromatosis type 1 and plexiform neurofibromas: a retrospective database analysis of a medicaid population

OBJECTIVES

The objectives of this study were to describe the characteristics and initial treatment patterns, healthcare resource use (HCRU), and costs of patients newly diagnosed with neurofibromatosis type 1 (NF1)-related plexiform neurofibromas (PN).

METHODS

This was a retrospective study of individuals enrolled in the IBM MarketScan Multi-State Medicaid database from 1 October 2014 to 31 December 2017. Patients aged ≤18 years at the index date (first diagnosis of NF1 or PN, whichever occurred later) with at least 1 ICD-10-CM diagnosis code for both NF1 and PN were included. All-cause HCRU and the associated direct costs during the follow-up period were calculated per patient per year (PPPY) in 2018 USD.

RESULTS

A total of 383 patients were included with a mean follow-up of 448 days. Most patients were diagnosed by a specialist (63.5%). During the follow-up period, pain medications were used by 58.5% of patients, 25.1% were treated with chemotherapy, 7.1% received surgery for PN, 1.6% received MEK inhibitors, and 0.8% received radiation. Mean PPPY inpatient, outpatient, ER, pharmacy, and other visits were 1.4, 17.3, 1.6, 13.6, and 25.8, respectively. Mean ± SD (median) total PPPY healthcare costs were $17,275 ± $61,903 ($2889), with total medical costs of $14,628 ± $56,203 ($2334) and pharmacy costs of $2646 ± $13,303 ($26).

CONCLUSIONS

This study showed that many pediatric patients newly diagnosed with NF1 and PN were initially treated with supportive care only, highlighting a substantial unmet medical need. This study also highlights the considerable economic burden among patients with NF1 and PN.

MEK inhibitors in RASopathies

PURPOSE OF REVIEW

An early understanding of the role of the Ras/Raf/MEK/ERK signalling pathway in regulating cell proliferation has set the stage for the development of several potent and selective MEK inhibitors (MEKi). MEKi represent promising therapies for RAS-driven neoplasias and RASopathies associated with increased Ras/MAPK activity.

RECENT FINDINGS

Neurofibromatosis 1 (NF1) is a prototypic RASopathy in which early-phase clinical trials with MEKi have been successful in the treatment of plexiform neurofibromas (pNF) and low-grade gliomas (LGGs). The phase 2 trial (SPRINT) of selumetinib in pNF resulted in at least 20% reduction in the size of pNF from baseline in 71% of patients and was associated with clinically meaningful improvements. On the basis of this trial, selumetinib (Koselugo) received FDA approval for children 2 years of age and older with inoperable, symptomatic pNF. The phase 2 trial of selumetinib in LGG resulted in 40% partial response and 96% of patients had 2 years of progression-free survival.

SUMMARY

Given the potential of MEK inhibition as an effective and overall well tolerated medical treatment, the use of targeted agents in the NF1 population is likely to increase considerably. Future work on non-NF1 RASopathies should focus on developing preclinical models and defining endpoints for measurement of efficacy in order to conduct clinical trials.

Using real world data to support regulatory approval of drugs in rare diseases: A review of opportunities, limitations & a case example

Conducting clinical research in patients with rare diseases presents a variety of challenges. At the same time, rare diseases represent a large area of unmet medical need with a significant burden of morbidity throughout the world. One of the most common issues with designing clinical trials for rare disease populations is that the gold-standard randomized controlled trial design is often not feasible in these small and usually geographically dispersed populations. Real world data therefore has particular relevance in the rare disease setting, where it may be used as a comparator for single-arm treatment trials and in support of submissions to regulatory agencies for drugs to treat these conditions. In this report, we review the potential utility and limitations of external controls for regulatory approval of drugs in rare diseases and present a recent case example of the successful utilization of external controls in the Neurofibromatosis type 1 (NF1) population.

Surgery for Peripheral Nerve Sheath Tumours of the Buttocks, Legs and Feet in 90 Patients With Neurofibromatosis Type 1

BACKGROUND/AIM

Neurofibromatosis type 1 (NF1) is an autosomal dominant tumour predisposition syndrome that can cause plexiform neurofibromas (PNFs). This study examines the surgical procedures that have been performed on large PNFs of the lower extremities.

PATIENTS AND METHODS

Surgical procedures on the lower extremity performed on 90 patients with NF1 with PNFs were evaluated. The topography of the tumours was classified according to dermatomes and functional units.

RESULTS

A total of 243 surgical interventions on the regions of interest were performed. Neurological complications were rarely noted and usually occurred temporarily. There was no preference for dermatomes affected by PNF. The proportion of patients with malignant peripheral nerve sheath tumours (MPNSTs) in this group was 4/90 (4.4%).

CONCLUSION

PNFs often require repeated local interventions to achieve the treatment goal. Local tumour recurrences are to be expected even after extensive tumour reduction. Rapid tumour growth combined with new pain sensations can be signs of a MPNST.

Biallelic NF1 inactivation in high grade serous ovarian cancers from patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a multisystem disorder caused by germline heterozygous NF1 loss-of-function variants. The NF1 gene encodes neurofibromin, a RAS GTPase-activating protein, which functions by down-regulating RAS/RAF/MAPK-signalling pathways. Somatic NF1 aberrations frequently occur in sporadic ovarian cancer (OC), but the incidence of OC in NF1 patients is rare. Here we report the germline and somatic findings for two unrelated patients with NF1 and high-grade serous OC. Germline testing revealed a heterozygous NF1 pathogenic variant in each patient, c.7096_7101del (p.Asn2366_Phe2367del) and c.964delA (p.Ile322Leufs*54), respectively. No germline variants in well-established OC predisposition genes were detected, including BRCA1 and BRCA2. Tumor loss-of-heterozygosity analysis demonstrated loss of the wild type NF1 allele for both patients. Biallelic NF1 inactivation occurs as part of OC pathogenesis in NF1 patients. Although the penetrance of NF1-associated OC is insufficient to warrant risk-reducing interventions, our findings highlight the potential for therapies targeting the RAS/RAF/MAPK-signalling pathway for these cases.

Natural History and Disease Burden of Neurofibromatosis Type 1 with Plexiform Neurofibromas: A Systematic Literature Review

Neurofibromatosis type 1 (NF1) is an incurable genetic condition that frequently includes the development of plexiform neurofibromas (PNs) in patients. A systematic literature review was conducted to identify data on the natural history, disease burden, and treatment patterns among patients diagnosed with NF1 and PN, as well as to identify evidence gaps in these areas. MEDLINE and MEDLINE In-Process, Embase, and Cochrane Library Searches were searched using predefined terms. Potential references underwent two phases of screening by two independent researchers. A total of 39 references focusing on populations of patients with both NF1 and PN were included in this review. The wide range of PN-related complications creates a substantial quality-of-life (QOL) burden for patients, including pain, social functioning, physical function impact, stigma, and emotional distress. The severe burden of NF1 with PN on the QOL of patients demonstrates the high unmet need for an effective treatment option that can reduce tumor burden and improve QOL. The heterogeneity of measurement tools used to evaluate QOL and the gap in data evaluating the health economic burden of PN should be the focus of future research.

Trametinib therapy for children with neurofibromatosis type 1 and life-threatening plexiform neurofibroma or treatment-refractory low-grade glioma

Purpose

To describe a series of children with extensive PNF or treatment refractory PLGG treated on a compassionate basis with trametinib.

Methods

We report on six patients with NF‐1 treated with trametinib on a compassionate basis at British Columbia Children's Hospital since 2017. Data were collected retrospectively from the patient record. RAPNO and volumetric criteria were used to evaluate the response of intracranial and extracranial lesions, respectively.

Results

Subjects were 21 months to 14 years old at the time of initiation of trametinib therapy and 3/6 subjects are male. Duration of therapy was 4–28 months at the time of this report. All patients had partial response or were stable on analysis. Two patients with life‐threatening PNF had a partial radiographic response in tandem with significant clinical improvement and developmental catch up. One subject discontinued therapy after 6 months due to paronychia and inadequate response. The most common adverse effect (AE) was grade 1–2 paronychia or dermatitis in 5/6 patients. There were no grade 3 or 4 AEs. At the time of this report, five patients remain on therapy.

Conclusion

Trametinib is an effective therapy for advanced PNF and refractory PLGG in patients with NF‐1 and is well tolerated in children. Further data and clinical trials are required to assess tolerance, efficacy and durability of response, and length of treatment required in such patients.

Population pharmacokinetics and exposure-response of selumetinib and its N-desmethyl metabolite in pediatric patients with neurofibromatosis type 1 and inoperable plexiform neurofibromas

PURPOSE

Selumetinib (ARRY-142886) is a potent, selective, MEK1/2 inhibitor approved in the US for the treatment of children (≥ 2 years) with neurofibromatosis type 1 (NF1) and symptomatic, inoperable plexiform neurofibromas (PN). We characterized population pharmacokinetics (PK) of selumetinib and its active N-desmethyl metabolite, evaluated exposure-safety/efficacy relationships, and assessed the proposed therapeutic dose of 25 mg/m² bid based on body surface area (BSA) in this patient population.

METHODS

Population PK modeling and covariate analysis (demographics, formulation, liver enzymes, BSA, patients/healthy volunteers) were based on pooled PK data from adult healthy volunteers (n = 391), adult oncology patients (n = 83) and pediatric patients with NF1-PN (n = 68). Longitudinal selumetinib/metabolite exposures were predicted with the final model. Exposure-safety/efficacy analyses were applied to pediatric patients (dose levels: 20, 25, 30 mg/m² bid).

RESULTS

Selumetinib and metabolite concentration-time courses were modeled using a joint compartmental model. Typical selumetinib plasma clearance was 11.6 L/h (95% CI 11.0-12.2 L/ h). Only BSA had a clinically relevant (> 20%) impact on exposure, supporting BSA-based administration in children. Selumetinib and metabolite exposures in responders (≥ 20% PN volume decrease from baseline) and non-responders were largely overlapping, with medians numerically higher in responders. No clear relationships between exposure and safety events were established; exposure was not associated with key adverse events (AEs) including rash acneiform, diarrhea, vomiting, and nausea.

CONCLUSION

Findings support continuous selumetinib 25 mg/m² bid in pediatric patients. Importantly, the updated dosing nomogram ensures that patients will receive a clinically active, yet tolerable, dose regardless of differences in BSA and allows dose reductions, if necessary.

Propranolol Specifically Suppresses the Viability of Tumorous Schwann Cells Derived from Plexiform Neurofibromas In Vitro

BACKGROUND/AIM

Plexiform neurofibromas (PNFs) are benign tumors of the periph eral nerves sheath, which can damage neighboring organs, impair functions, cause pain and serious maxillofacial disfigurement, and have a high risk of malignant transformation. Complete resection is usually not possible since PNFs often extend through multiple layers of tissue. Therefore, it is necessary and beneficial to find a reasonable drug treatment for PNFs. Propranolol-treatment is the first-line therapy for infantile hemangiomas and the side effects are reversible and mostly benign. The present study aimed to examine the possible effect of propranolol for suppressing PNFs in vitro.

MATERIALS AND METHODS

Paired primary Schwann-cell-rich cultures and fibroblast-rich cultures were obtained from 4 PNFs of unrelated patients. Human Schwann cells (HSCs) were used as the control. These cultures were treated with propranolol for 7 days at concentrations up to 150 μM. Cells were then measured for their viability and immune-stained with S100 to label the tumorous Schwann cells.

RESULTS

Propranolol inhibited the viability of the tumorous Schwann cells in a dose-dependent manner, while did not substantially suppress viability of the non-tumorous fibroblasts derived from the same PNFs.

CONCLUSION

Propranolol may provide a treatment option for suppressing the growth of PNFs.

Whole-body magnetic resonance imaging in children - how and why? A systematic review

Whole-body magnetic resonance imaging (MRI) is increasingly being used for a number of indications. Our aim was to review and describe indications and scan protocols for diagnostic value of whole-body MRI for multifocal disease in children and adolescents, we conducted a systematic search in Medline, Embase and Cochrane for all published papers until November 2018. Relevant subject headings and free text words were used for the following concepts: 1) whole-body, 2) magnetic resonance imaging and 3) child and/or adolescent. Included were papers in English with a relevant study design that reported on the use and/or findings from whole-body MRI examinations in children and adolescents. This review includes 54 of 1,609 papers identified from literature searches. Chronic nonbacterial osteomyelitis, lymphoma and metastasis were the most frequent indications for performing a whole-body MRI. The typical protocol included a coronal STIR (short tau inversion recovery) sequence with or without a coronal T1-weighted sequence. Numerous studies lacked sufficient data for calculating images resolution and only a few studies reported the acquired voxel volume, making it impossible for others to reproduce the protocol/images. Only a minority of the included papers assessed reliability tests and none of the studies documented whether the use of whole-body MRI affected mortality and/or morbidity. Our systematic review confirms significant variability of technique and the lack of proven validity of MRI findings. The information could potentially be used to boost attempts towards standardization of technique, reporting and guidelines development.

Treatment, Resource Use and Costs Among Pediatric Patients with Neurofibromatosis Type 1 and Plexiform Neurofibromas

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic condition which predisposes individuals to tumors of the nervous system, skin, bones, and eyes. Plexiform neurofibromas (PNs) occur in 20-50% of NF1 cases, causing multiple morbidities and conferring a risk of malignancy. NF1 with PN is poorly characterized in the literature with regard to treatment patterns, healthcare resource utilization, and costs in the real world.

Methods

This was a retrospective analysis of data from a commercial claims database in the US between October 2014 and March 2018. Persons with at least 1 diagnostic code for both NF1 and PN, aged ≤18 years on the index date, and continuously enrolled for ≥12 months before the index date were included. The index date was defined as the date of the first diagnosis of NF1 or PN during the study period, whichever occurred later. Healthcare resource utilization during follow-up included outpatient, inpatient, emergency room (ER), and pharmacy encounters; corresponding costs were calculated as the mean per patient per year (PPPY) in 2018 US dollars. Treatments were classified as PN surgery, pain medication, chemotherapy, radiotherapy, and targeted therapies. All analyses were descriptive.

Results

A total of 301 patients were included. In the follow-up period, nearly all patients (99.7%) had outpatient visits, while 81.1% had pharmacy visits, 25.2% had ER visits, and 13.0% had inpatient visits. Mean ± SD [median] total healthcare costs PPPY were $38,292 ± $80,556 [$16,037]. During follow-up, 44.2% of patients used pain medications, 23.9% received chemotherapy, 5.0% underwent surgery for PN, 1.3% received radiotherapy, and 1.0% received targeted therapies.

Conclusion

Commercially insured pediatric patients diagnosed with NF1 and PN were treated primarily with supportive care, highlighting a substantial unmet need in the United States.

Current status of MEK inhibitors in the treatment of plexiform neurofibromas

BACKGROUND

Neurofibromatosis type 1 (NF1)-related plexiform neurofibromas (pNF) can be debilitating and until recently, surgery was the only potentially effective therapy for these tumors.

METHODS

We review critical steps in the path towards the FDA approval of the first medical therapy for NF1 pNF and the current status of MEK inhbitor therapy.

RESULTS

Sustained efforts by the NF community have resulted in a detailed understanding of the natural history and biology of NF1-related peripheral nerve sheath tumors. This work provided the basis for the development of meaningful clinical trials targeting pNF. Inhibition of the RAS/MAPK signaling pathway with MEK inhibitors identified the first medical therapy which resulted in shrinkage in the majority of children with NF1 and large inoperable pNF. Based on this finding and subsequent demonstration of clinical benefit, the MEK inhibitor selumetinib recently received approval by the United States Food and Drug Administration (FDA) for children with symptomatic pNF.

CONCLUSIONS

Sustained efforts and collaborations have resulted in identification of MEK inhibitors as effective therapy for NF1 pNF. Future work work will be directed at prevention of pNF morbidity and deepening the reponse in symptomatic pNF.

Longitudinal evaluation of peripheral nerve sheath tumors in neurofibromatosis type 1: growth analysis of plexiform neurofibromas and distinct nodular lesions

BACKGROUND

Understanding the natural history of non-malignant peripheral nerve sheath tumors (PNSTs) in neurofibromatosis type 1 (NF1) is critical to optimal clinical care and the development of meaningful clinical trials.

METHODS

We longitudinally analyzed growth of plexiform neurofibromas (PNs) and of PNSTs with distinct nodular appearance (distinct nodular lesions [DNLs]) using volumetric MRI analysis in patients enrolled on a natural history study (NCT00924196).

RESULTS

DNLs were observed in 58/122 (45.6%) patients (median 2 DNLs/patient). In DNLs that developed during follow-up, median age of development was 17 years. A moderate negative correlation was observed between the estimated PN growth rate and patients' age at initial MRI (Spearman's r [95% CI]: -0.60 [-0.73, -0.43], n = 70), whereas only a weak correlation was observed for DNLs (Spearman's r [95% CI]: -0.25 [-0.47, 0.004]; n = 61). We observed a moderate negative correlation between tumor growth rate and baseline tumor volume for PNs and DNLs (Spearman's r [95% CI]: -0.52 [-0.67, -0.32] and -0.61 [-0.75, -0.42], respectively). Spontaneous tumor volume reduction was observed in 10 PNs and 7 DNLs (median decrease per year, 3.6% and 7.3%, respectively).

CONCLUSION

We corroborate previously described findings that most rapidly growing PNs are observed in young children. DNLs tend to develop later in life and their growth is minimally age related. Distinct growth characteristics of PNs and DNLs suggest that these lesions have a different biology and may require different clinical management and clinical trial design. In a subset of PNs and DNLs, slow spontaneous regression in tumor volume was seen.

Cognitive functioning and pain interference mediate pain predictive effects on health-related quality of life in pediatric patients with Neurofibromatosis Type 1

OBJECTIVES

The objective was to investigate the serial mediating effects of perceived cognitive functioning and pain interference in daily living in the relationship between perceived pain and overall generic health-related quality of life (HRQOL) in children, adolescents, and young adults with Neurofibromatosis Type 1 (NF1).

METHODS

The Pain, Cognitive Functioning, and Pain Impact Scales from the PedsQL Neurofibromatosis Type 1 Module and the PedsQL 4.0 Generic Core Scales were completed in a multi-site national study by 323 patients ages 5-25 and 335 parents. A serial multiple mediator model analysis was conducted to test the hypothesized sequential mediating effects of cognitive functioning and pain interference as intervening variables in the association between pain as a predictor variable and overall generic HRQOL.

RESULTS

Pain predictive effects on overall generic HRQOL were serially mediated by cognitive functioning and pain interference. In predictive analytics models utilizing hierarchical multiple regression analyses with age and gender demographic covariates, pain, cognitive functioning and pain interference accounted for 66% of the variance in patient-reported generic HRQOL and 57% of the variance in parent proxy-reported generic HRQOL (P < 0.001), reflecting large effect sizes.

CONCLUSIONS

Cognitive functioning and pain interference explain in part the mechanism of pain predictive effects on overall generic HRQOL in pediatric patients with NF1. Identifying NF1-specific pain, cognitive functioning, and pain interference as salient predictors of overall generic HRQOL from the patient and parent perspective facilitates a family-centered orientation to the comprehensive care of children, adolescents, and young adults with NF1.

Early administration of imatinib mesylate reduces plexiform neurofibroma tumor burden with durable results after drug discontinuation in a mouse model of neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by plexiform neurofibromas (pNF), which are thought to be congenital tumors that arise in utero and enlarge throughout life. Genetic studies in murine models delineated an indispensable role for the stem cell factor (SCF)/c-kit pathway in pNF initiation and progression. A subsequent phase 2 clinical trial using imatinib mesylate to inhibit SCF/c-kit demonstrated tumor shrinkage in a subset of preexisting pNF; however, imatinib's role on preventing pNF development has yet to be explored.

PROCEDURE

We evaluated the effect of imatinib dosed at 10-100 mg/kg/day for 12 weeks to one-month-old Nf1^flox/flox ;PostnCre(+) mice, prior to onset of pNF formation. To determine durability of response, we then monitored for pNF growth at later time points, comparing imatinib- with vehicle-treated mice. We assessed gross and histopathological analysis of tumor burden.

RESULTS

Imatinib administered preventatively led to a significant decrease in pNF number, even at doses as low as 10 mg/kg/day. Tumor development continued to be significantly inhibited after cessation of imatinib dosed at 50 and 100 mg/kg/day. In the cohort of treated mice that underwent prolonged follow-up, the size of residual tumors was significantly reduced as compared with age-matched littermates that received vehicle control.

CONCLUSIONS

Early administration of imatinib inhibits pNF genesis in vivo, and effects are sustained after discontinuation of therapy. These findings may guide clinical use of imatinib in young NF1 patients prior to the substantial development of pNF.

The impact of host immune cells on the development of neurofibromatosis type 1: The abnormal immune system provides an immune microenvironment for tumorigenesis

AbstractThe immune system plays an essential role in the development of tumors, which has been demonstrated in multiple types of cancers. Consistent with this, immunotherapies with targets that disrupt these mechanisms and turn the immune system against developing cancers have been proven effective. In neurofibromatosis type 1 (NF1), an autosomal dominant genetic disorder, the understanding of the complex interactions of the immune system is incomplete despite the discovery of the pivotal role of immune cells in the tumor microenvironment. Individuals with NF1 show a loss of the NF1 gene in nonneoplastic cells, including immune cells, and the aberrant immune system exhibits intriguing interactions with NF1. This review aims to provide an update on recent studies showing the bilateral influences of NF1 mutations on immune cells and how the abnormal immune system promotes the development of NF1 and NF1-related tumors. We then discuss the immune receptors major histocompatibility complex class I and II and the PD-L1 mechanism that shield NF1 from immunosurveillance and enable the immune escape of tumor tissues. Clarification of the latest understanding of the mechanisms underlying the effects of the abnormal immune system on promoting the development of NF1 will indicate potential future directions for further studies and new immunotherapies.

Advanced pharmacological therapies for neurofibromatosis type 1-related tumors

Neurofibromatosis Type 1 (NF1) is an autosomal dominant tumor-predisposition disorder that is caused by a heterozygous loss of function variant in the NF1 gene, which encodes a protein called neurofibromin. The absence of neurofibromin causes increased activity in the Rat sarcoma protein (RAS) signalling pathway, which results in an increased growth and cell proliferation. As a result, both oncological and non-oncological comorbidities contribute to a high morbidity and mortality in these patients. Optic pathways gliomas, plexiform neurofibromas and malignant peripheral nerve sheath tumor (MPNST) are the most frequent NF1-associated tumors. The treatment of these complications is often challenging, since surgery may not be feasible due to the location, size, and infiltrative nature of these tumors, and standard chemotherapy or radiotherapy are burdened by significant toxicity and risk for secondary malignancies. For these reasons, following the novel discoveries of the pathophysiological mechanisms that lead to cell proliferation and tumorigenesis in NF1 patients, emerging drugs targeting specific signalling pathways (i.e. the MEK/ERK cascade), have been developed with promising results.

Selumetinib in Children with Inoperable Plexiform Neurofibromas

BACKGROUND

No approved therapies exist for inoperable plexiform neurofibromas in patients with neurofibromatosis type 1.

METHODS

We conducted an open-label, phase 2 trial of selumetinib to determine the objective response rate among patients with plexiform neurofibromas and to assess clinical benefit. Children with neurofibromatosis type 1 and symptomatic inoperable plexiform neurofibromas received oral selumetinib twice daily at a dose of 25 mg per square meter of body-surface area on a continuous dosing schedule (28-day cycles). Volumetric magnetic resonance imaging and clinical outcome assessments (pain, quality of life, disfigurement, and function) were performed at least every four cycles. Children rated tumor pain intensity on a scale from 0 (no pain) to 10 (worst pain imaginable).

RESULTS

A total of 50 children (median age, 10.2 years; range, 3.5 to 17.4) were enrolled from August 2015 through August 2016. The most frequent neurofibroma-related symptoms were disfigurement (44 patients), motor dysfunction (33), and pain (26). A total of 35 patients (70%) had a confirmed partial response as of March 29, 2019, and 28 of these patients had a durable response (lasting ≥1 year). After 1 year of treatment, the mean decrease in child-reported tumor pain-intensity scores was 2 points, considered a clinically meaningful improvement. In addition, clinically meaningful improvements were seen in child-reported and parent-reported interference of pain in daily functioning (38% and 50%, respectively) and overall health-related quality of life (48% and 58%, respectively) as well as in functional outcomes of strength (56% of patients) and range of motion (38% of patients). Five patients discontinued treatment because of toxic effects possibly related to selumetinib, and 6 patients had disease progression. The most frequent toxic effects were nausea, vomiting, or diarrhea; an asymptomatic increase in the creatine phosphokinase level; acneiform rash; and paronychia.

CONCLUSIONS

In this phase 2 trial, most children with neurofibromatosis type 1 and inoperable plexiform neurofibromas had durable tumor shrinkage and clinical benefit from selumetinib. (Funded by the Intramural Research Program of the National Institutes of Health and others; ClinicalTrials.gov number, NCT01362803.).

Towards a neurobiological understanding of pain in neurofibromatosis type 1: mechanisms and implications for treatment

Neurofibromatosis type 1 (NF1) is the most common of a group of rare diseases known by the term, "Neurofibromatosis," affecting 1 in 3000 to 4000 people. NF1 patients present with, among other disease complications, café au lait patches, skin fold freckling, Lisch nodules, orthopedic complications, cutaneous neurofibromas, malignant peripheral nerve sheath tumors, cognitive impairment, and chronic pain. Although NF1 patients inevitably express pain as a debilitating symptom of the disease, not much is known about its manifestation in the NF1 disease, with most current information coming from sporadic case reports. Although these reports indicate the existence of pain, the molecular signaling underlying this symptom remains underexplored, and thus, we include a synopsis of the literature surrounding NF1 pain studies in 3 animal models: mouse, rat, and miniswine. We also highlight unexplored areas of NF1 pain research. As therapy for NF1 pain remains in various clinical and preclinical stages, we present current treatments available for patients and highlight the importance of future therapeutic development. Equally important, NF1 pain is accompanied by psychological complications in comorbidities with sleep, gastrointestinal complications, and overall quality of life, lending to the importance of investigation into this understudied phenomenon of NF1. In this review, we dissect the presence of pain in NF1 in terms of psychological implication, anatomical presence, and discuss mechanisms underlying the onset and potentiation of NF1 pain to evaluate current therapies and propose implications for treatment of this severely understudied, but prevalent symptom of this rare disease.