Human fetal cerebellar cell atlas informs medulloblastoma origin and oncogenesis.

Medulloblastoma (MB) is the most common malignant childhood brain tumour1,2, yet the origin of the most aggressive subgroup-3 form remains elusive, impeding development of effective targeted treatments. Previous analyses of mouse cerebella3-5 have not fully defined the compositional heterogeneity of MBs. Here we undertook single-cell profiling of freshly isolated human fetal cerebella to establish a reference map delineating hierarchical cellular states in MBs. We identified a unique transitional cerebellar progenitor connecting neural stem cells to neuronal lineages in developing fetal cerebella. Intersectional analysis revealed that the transitional progenitors were enriched in aggressive MB subgroups, including group 3 and metastatic tumours. Single-cell multi-omics revealed underlying regulatory networks in the transitional progenitor populations, including transcriptional determinants HNRNPH1 and SOX11, which are correlated with clinical prognosis in group 3 MBs. Genomic and Hi-C profiling identified de novo long-range chromatin loops juxtaposing HNRNPH1/SOX11-targeted super-enhancers to cis-regulatory elements of MYC, an oncogenic driver for group 3 MBs. Targeting the transitional progenitor regulators inhibited MYC expression and MYC-driven group 3 MB growth. Our integrated single-cell atlases of human fetal cerebella and MBs show potential cell populations predisposed to transformation and regulatory circuitries underlying tumour cell states and oncogenesis, highlighting hitherto unrecognized transitional progenitor intermediates predictive of disease prognosis and potential therapeutic vulnerabilities.

Low-grade glioma in children with neurofibromatosis type 1: surveillance, treatment indications, management, and future directions.

Neurofibromatosis type 1 (NF1) is an autosomal dominant cancer predisposition syndrome characterized by the development of both central and peripheral nervous system tumors. Low-grade glioma (LGG) is the most prevalent central nervous system tumor occurring in children with NF1, arising most frequently within the optic pathway, followed by the brainstem. Historically, treatment of NF1-LGG has been limited to conventional cytotoxic chemotherapy and surgery. Despite treatment with chemotherapy, a subset of children with NF1-LGG fail initial therapy, have a continued decline in function, or recur. The recent development of several preclinical models has allowed for the identification of novel, molecularly targeted therapies. At present, exploration of these novel precision-based therapies is ongoing in the preclinical setting and through larger, collaborative clinical trials. Herein, we review the approach to surveillance and management of NF1-LGG in children and discuss upcoming novel therapies and treatment protocols.

A new era for myelin research in Neurofibromatosis type 1.

Evidence for myelin regulating higher-order brain function and disease is rapidly accumulating; however, defining cellular/molecular mechanisms remains challenging partially due to the dynamic brain physiology involving deep changes during development, aging, and in response to learning and disease. Furthermore, as the etiology of most neurological conditions remains obscure, most research models focus on mimicking symptoms, which limits understanding of their molecular onset and progression. Studying diseases caused by single gene mutations represents an opportunity to understand brain dys/function, including those regulated by myelin. Here, we discuss known and potential repercussions of abnormal central myelin on the neuropathophysiology of Neurofibromatosis Type 1 (NF1). Most patients with this monogenic disease present with neurological symptoms diverse in kind, severity, and onset/decline, including learning disabilities, autism spectrum disorders, attention deficit and hyperactivity disorder, motor coordination issues, and increased risk for depression and dementia. Coincidentally, most NF1 patients show diverse white matter/myelin abnormalities. Although myelin-behavior links were proposed decades ago, no solid data can prove or refute this idea yet. A recent upsurge in myelin biology understanding and research/therapeutic tools provides opportunities to address this debate. As precision medicine moves forward, an integrative understanding of all cell types disrupted in neurological conditions becomes a priority. Hence, this review aims to serve as a bridge between fundamental cellular/molecular myelin biology and clinical research in NF1.

An unusual presentation of bilateral optic pathway glioma in Crouzon Syndrome.

Crouzon Syndrome is a genetic craniosynostosis disorder associated with a high risk of ophthalmologic sequelae secondary to structural causes. However, ophthalmologic disorders due to intrinsic nerve aberrations in Crouzon Syndrome have not been described. Optic pathway gliomas (OPGs) are low grade gliomas that are intrinsic to the visual pathway, frequently associated with Neurofibromatosis type 1 (NF-1). OPGs involving both optic nerves without affecting the optic chiasm are rarely seen outside of NF-1. We report an unusual case of bilateral optic nerve glioma without chiasmatic involvement in a 17-month-old male patient with Crouzon Syndrome without any clinical or genetic findings of NF-1. This case suggests that close ophthalmologic follow up and orbital MRIs may benefit patients with Crouzon Syndrome.

Overcoming barriers to establishing autopsy procurement programs in pediatric patients with central nervous system tumors: a call to develop regional centers.

BACKGROUND: While autopsy-repository programs with a variety of pediatric central nervous system (CNS) tumor types are a critical resource for preclinical neuro-oncology research, few exist and there is no published guidance on how to develop one. The goal of this prospective Pediatric Brain Tumor Repository (PBTR) study was to develop such a program at Cincinnati Children's Hospital Medical Center (CCHMC) and then publish the quantitative and experiential data as a guide to support the development of similar programs. METHODS: Protocols and infrastructure were established-to educate oncologists and families, establish eligibility, obtain consent, address pre- and post-autopsy logistics (e.g., patient and tissue transportation), process and authenticate tissue samples, and collect and analyze data. RESULTS: Of the 129 pediatric CNS tumor patients at CCHMC who died between 2013 and 2018, 109 were eligible for our study. Of these, 74% (81 of 109) were approached for PBTR donation, and 68% (55 of 81) consented. In the final year of the study, approach and consent rates were 93% and 85%, respectively. Median time from death to autopsy (postmortem interval, PMI) was 10 h (range, 1.5-30). In the outpatient setting, PMI increased with distance (from the hospice/home where the patient died to CCHMC). In all patients, PMI appeared to be lower, when consent was obtained more than 24 h before death. CONCLUSIONS: Procurement of autopsy specimens need not be a barrier in neuro-oncology research. Regional centers, strict timing-of-consent, patient education, and dedicated staff are all needed to minimize PMI and, thereby, increase the value of the procured tissue for an array of basic and translational research applications.

Trametinib-associated Hyponatremia in a Child With Low-grade Glioma is Not Seen Following Treatment With Alternative MEK Inhibitor.

Molecularly targeted therapy with MEK inhibitors has been increasingly incorporated into the treatment of pediatric low-grade gliomas, but this promising therapy is associated with distinctive and specific toxicities. Understanding life-threatening MEK inhibitor toxicities and their management is critical to MEK inhibitor safety, especially among young children. This report describes severe hyponatremia associated with trametinib in an infant with progressive low-grade glioma without underlying endocrine dysfunction, which recurred despite significant dose reduction. Therapy with an alternative MEK inhibitor, binimetinib, provided excellent tumor response without hyponatremia, suggesting that some toxicities may be avoided by changing MEK inhibitor agents within the same class.

Response assessment in paediatric low-grade glioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group.

Paediatric low-grade gliomas (also known as pLGG) are the most common type of CNS tumours in children. In general, paediatric low-grade gliomas show clinical and biological features that are distinct from adult low-grade gliomas, and the developing paediatric brain is more susceptible to toxic late effects of the tumour and its treatment. Therefore, response assessment in children requires additional considerations compared with the adult Response Assessment in Neuro-Oncology criteria. There are no standardised response criteria in paediatric clinical trials, which makes it more difficult to compare responses across studies. The Response Assessment in Pediatric Neuro-Oncology working group, consisting of an international panel of paediatric and adult neuro-oncologists, clinicians, radiologists, radiation oncologists, and neurosurgeons, was established to address issues and unique challenges in assessing response in children with CNS tumours. We established a subcommittee to develop consensus recommendations for response assessment in paediatric low-grade gliomas. Final recommendations were based on literature review, current practice, and expert opinion of working group members. Consensus recommendations include imaging response assessments, with additional guidelines for visual functional outcomes in patients with optic pathway tumours. As with previous consensus recommendations, these recommendations will need to be validated in prospective clinical trials.

Late morbidity and mortality in adult survivors of childhood glioma with neurofibromatosis type 1: report from the Childhood Cancer Survivor Study.

PURPOSE: Neurofibromatosis type 1 (NF1) is associated with tumor predisposition and nonmalignant health conditions. Whether survivors of childhood cancer with NF1 are at increased risk for poor long-term health outcomes is unknown. METHODS: One hundred forty-seven 5+ year survivors of childhood glioma with NF1 from the Childhood Cancer Survivor Study were compared with 2629 non-NF1 glioma survivors and 5051 siblings for late mortality, chronic health conditions, and psychosocial, neurocognitive, and socioeconomic outcomes. RESULTS: Survivors with NF1 (age at diagnosis: 6.8 ± 4.8 years) had greater cumulative incidence of late mortality 30 years after diagnosis (46.3% [95% confidence interval: 23.9-62.2%]) compared with non-NF1 survivors (18.0% [16.1-20.0%]) and siblings (0.9% [0.6-1.2%]), largely due to subsequent neoplasms. Compared with survivors without NF1, those with NF1 had more severe/life-threatening chronic conditions at cohort entry (46.3% [38.1-54.4%] vs. 30.8% [29.1-32.6%]), but similar rates of new conditions during follow-up (rate ratio: 1.26 [0.90-1.77]). Survivors with NF1 were more likely to report psychosocial impairments, neurocognitive deficits, and socioeconomic difficulties compared with survivors without NF1. CONCLUSIONS: Late mortality among glioma survivors with NF1 is twice that of other survivors, due largely to subsequent malignancies. Screening, prevention, and early intervention for chronic health conditions and psychosocial and neurocognitive deficits may reduce long-term morbidity in this vulnerable population.

Molecular markers and targeted therapy in pediatric low-grade glioma.

INTRODUCTION: Recently discovered molecular alterations in pediatric low-grade glioma have helped to refine the classification of these tumors and offered novel targets for therapy. Genetic aberrations may combine with histopathology to offer new insights into glioma classification, gliomagenesis and prognosis. Therapies targeting common genetic aberrations in the MAPK pathway offer a novel mechanism of tumor control that is currently under study. METHODS: We have reviewed common molecular alterations found in pediatric low-grade glioma as well as recent clinical trials of MEK and BRAF inhibitors. RESULTS: In this topic review, we examine the current understanding of molecular alterations in pediatric low-grade glioma, as well as their role in diagnosis, prognosis and therapy. We summarize current data on the efficacy of targeted therapies in pediatric low-grade gliomas, as well as the many unanswered questions that these new discoveries and therapies raise. CONCLUSIONS: The identification of driver alterations in pediatric low-grade glioma and the development of targeted therapies have opened new therapeutic avenues for patients with low-grade gliomas.

A phase I/II study of ribociclib following radiation therapy in children with newly diagnosed diffuse intrinsic pontine glioma (DIPG).

PURPOSE: Cyclin-dependent kinase-retinoblastoma (CDK-RB) pathway is dysregulated in some diffuse intrinsic pontine gliomas (DIPG). We evaluated safety, feasibility, and early efficacy of the CDK4/6-inhibitor ribociclib, administered following radiotherapy in newly-diagnosed DIPG patients. METHODS: Following radiotherapy, eligible patients received ribociclib in 28-day cycles (350 mg/m2; 21 days on/7 days off). Feasibility endpoints included tolerability for at least 6 courses, and a less than 2-week delay in restarting therapy after 1 dose reduction. Early efficacy was measured by 1-year and median overall survival (OS). Patient/parent-by-proxy reported outcomes measurement information system (PROMIS) assessments were completed prospectively. RESULTS: The study included 10 evaluable patients, 9 DIPG and 1 diffuse midline glioma (DMG)-all 3.7 to 19.8 years of age. The median number of courses was 8 (range 3-14). Three patients required dose reduction for grade-4 neutropenia, and 1 discontinued therapy for hematological toxicity following course 4. The most common grade-3/4 toxicity was myelosuppression. After 2 courses, MRI evaluations in 4 patients revealed increased necrotic volume, associated with new neurological symptoms in 3 patients. The 1-year and median OS for DIPG was 89% and 16.1 months (range 10-30), respectively; the DMG patient died at 6 months post-diagnosis. Five patients donated brain tissue and tumor; 3 were RB+ . CONCLUSIONS: Ribociclib administered following radiotherapy is feasible in DIPG and DMG. Increased tumor necrosis may represent a treatment effect. These data warrant further prospective volumetric analyses of tumors with necrosis. Feasibility and stabilization findings support further investigation of ribociclib in combination therapies. TRIAL REGISTRATION: NCT02607124.

Management of pediatric low-grade glioma.

PURPOSE OF REVIEW: Pediatric low-grade gliomas (pLGGs) have been treated with similar therapies for the last 30 years. Recent biological insights have allowed a new generation of targeted therapies to be developed for these diverse tumors. At the same time, technological advances may redefine the late toxicities associated with radiation therapy. Understanding recent developments in pLGG therapy is essential to the management of these common pediatric tumors. RECENT FINDINGS: It is now well understood that aberrations of the mitogen-activated protein kinase pathway are key to oncogenesis in low-grade gliomas. This understanding, along with the development of available targeted agents, have heralded a new era of understanding and treatment for these patients. Promising, sustained responses are now being seen in early phase trials among patients with multiply recurrent/progressive disease. Also, newer and highly conformal radiation approaches such as proton beam radiotherapy maintain efficacy of radiation but limit radiation-associated toxicities. SUMMARY: Novel therapies offer the potential for tumor control with greatly reduced toxicities. However, late effects of these therapies are just now being explored. Improved radiation approaches and targeted agents have the potential to redefine traditional therapy for pLGG.

Magnetic Resonance Fingerprinting to Characterize Childhood and Young Adult Brain Tumors.

OBJECT: Magnetic resonance fingerprinting (MRF) allows rapid, simultaneous mapping of T1 and T2 relaxation times and may be an important diagnostic tool to measure tissue characteristics in pediatric brain tumors. We examined children and young adults with primary brain tumors to determine whether MRF can discriminate tumor from normal-appearing white matter and distinguish tumor grade. METHODS: MRF was performed in 23 patients (14 children and 9 young adults) with brain tumors (19 low-grade glioma, 4 high-grade tumors). T1 and T2 values were recorded in regions of solid tumor (ST), peritumoral white matter (PWM), and contralateral white matter (CWM). Nonparametric tests were used for comparison between groups and regions. RESULTS: Median scan time for MRF and a sequence for tumor localization was 11 min. MRF-derived T1 and T2 values distinguished ST from CWM (T1: 1,444 ± 254 ms vs. 938 ± 96 ms, p = 0.0002; T2: 61 ± 22 ms vs. 38 ± 9 ms, p = 0.0003) and separated high-grade tumors from low-grade tumors (T1: 1,863 ± 70 ms vs. 1,355 ± 187 ms, p = 0.007; T2: 90 ± 13 ms vs. 56 ± 19 ms, p = 0.013). PWM was distinct from CWM (T1: 1,261 ± 359 ms vs. 933 ± 104 ms, p = 0.0008; T2: 65 ± 51 ms vs. 38 ± 8 ms, p = 0.008), as well as from tumor (T1: 1,261 ± 371 ms vs. 1,462 ± 248 ms, p = 0.047). CONCLUSIONS: MRF is a fast sequence that can rapidly distinguish important tissue components in pediatric brain tumor patients. MRF-derived T1 and T2 distinguished tumor from normal-appearing white matter, differentiated tumor grade, and found abnormalities in peritumoral regions. MRF may be useful for rapid quantitative measurement of tissue characteristics and distinguish tumor grade in children and young adults with brain tumors.

2016 Children's Tumor Foundation conference on neurofibromatosis type 1, neurofibromatosis type 2, and schwannomatosis.

Organized and hosted by the Children's Tumor Foundation (CTF), the Neurofibromatosis (NF) conference is the premier annual gathering for clinicians and researchers interested in neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis (SWN). The 2016 edition constituted a blend of clinical and basic aspects of NF research that helped in clarifying different advances in the field. The incorporation of next generation sequencing is changing the way genetic diagnostics is performed for NF and related disorders, providing solutions to problems like genetic heterogeneity, overlapping clinical manifestations, or the presence of mosaicism. The transformation from plexiform neurofibroma (PNF) to malignant peripheral nerve sheath tumor (MPNST) is being clarified, along with new management and treatments for benign and premalignant tumors. Promising new cellular and in vivo models for understanding the musculoskeletal abnormalities in NF1, the development of NF2 or SWN associated schwannomas, and clarifying the cells that give rise to NF1-associated optic pathway glioma were presented. The interaction of neurofibromin and SPRED1 was described comprehensively, providing functional insight that will help in the interpretation of pathogenicity of certain missense variants identified in NF1 and Legius syndrome patients. Novel promising imaging techniques are being developed, as well as new integrative and holistic management models for patients that take into account psychological, social, and biological factors. Importantly, new therapeutic approaches for schwannomas, meningiomas, ependymomas, PNF, and MPNST are being pursued. This report highlights the major advances that were presented at the 2016 CTF NF conference.

Choroid plexus tumors in adult and pediatric populations: the Cleveland Clinic and University Hospitals experience.

Choroid plexus tumors (CPT) are rare neoplasms accounting for 1-4% of all pediatric brain tumors. They are divided into choroid plexus papilloma (CPP), atypical choroid plexus papilloma (APP) and choroid plexus carcinoma (CPC). CPTs are known to primarily affect children less than 2 years of age. Gross total resection is the most important predictor of survival especially in CPC. Although small case series have been published, limited clinical data are available to describe treatment and outcome of CPTs. More clinical data would be necessary to complete the picture, particularly in populations that are not age limited. Here we share data from the two major hospitals in Cleveland to describe treatment and outcome of adult and pediatric patients. We performed a retrospective analysis of patients with CPT seen in Cleveland Clinic from 1990 to 2015 and at University Hospitals from 1994 to 2015. Results were compared to previously published historical controls. We identified 30 cases with CPT, including 22 pediatric and eight adult cases; 11 females and 19 males. The mean age at presentation was 12.4 years with a median age of 4.5 years (range 2 months-51 years). Gross total surgical resection was achieved in 22, subtotal resection in four, partial resection in two and unknown in two. The histology was CPP in 23 patients, two of whom developed recurrence requiring repeat resection and adjuvant therapy. Median event free survival (EFS) for CPP patients was 7.6 years. The histology was CPC in seven patients. All CPC patients were treated with adjuvant therapy. Median EFS of CPC patients was 4.4 years. Overall survival of all CPT patients was 100% with a median follow up of 7 years. A systematic literature review identified 1012 CPT patients treated from 1989 to 2013. The mean and median age of CPT patients was 13 and 3 years respectively. The median survival of 541 CPP patients was undefined vs. 2.7 years for the 452 CPC patients. The difference between the two populations was highly significant (p < 0.001). Kaplan-Meier survival curves comparing CPTs at Cleveland Clinic and University Hospitals versus a systematic literature review showed a statistically significant advancement in overall survival among the patients treated at Cleveland Clinic and University Hospitals. Our data are consistent with the literature review regarding epidemiology, clinical presentation, and treatment modalities but differed in regards to survival. Differences in survival may be related to different methods of data collection or details in patient care.

Incidence and survival trends for medulloblastomas in the United States from 2001 to 2013.

Population-based data examining recent epidemiological trends in medulloblastoma, the most common pediatric brain malignancy, are limited. Therefore, we sought to examine recent population-level trends in medulloblastoma incidence and survival. Central Brain Tumor Registry of the United States (CBTRUS) data were analyzed from 2001 to 2013. Age-adjusted incidence rates (IR) and annual percent changes (APCs) with 95% confidence intervals (CI) were calculated by age, sex, and race. Relative survival rates were calculated by age, sex, and race using Surveillance, Epidemiology and End-Results (SEER) registries; subsets of CBTRUS data. Kaplan-Meier and Cox proportional hazards models were used to examine survival differences. Medulloblastoma incidence remained relatively stable from 2001 to 2013, with minor fluctuations from 2001 to 2009 (APC = 2.2, 95% CI 0.8, 3.5) and 2009-2013 (APC = -4.1, 95% CI -7.5, -0.6). Incidence was highest in patients aged 1-4 years at diagnosis, but patients aged 10-14 years showed increased incidence from 2000 to 2013 (APC = 3.2, 95% CI 0.6, 5.8). Males displayed higher IR relative to females (males: 0.16 vs. females: 0.12), except in patients <1 year-old. Compared to Whites, Blacks displayed a non-significant increase in incidence (APC = 1.7, 95% CI -0.4, 4.0) and in mortality risk (hazard ratio for survival = 0.74; p = 0.09). The current study reports no overall change in medulloblastoma incidence from 2001 to 2013. Male and female patients <1 year-old had equal medulloblastoma incidence rates and poor 5-year relative survival compared to other ages. Non-significant trends in the data suggest disparities in medulloblastoma incidence and survival by race. Thus, analysis of tumor-specific trends by demographic variables can uncover clinically informative trends in cancer burden.

Optic Pathway Gliomas in Neurofibromatosis Type 1: An Update: Surveillance, Treatment Indications, and Biomarkers of Vision.

Optic pathway gliomas (OPGs) occur in 15%-20% of children with neurofibromatosis type 1 (NF1), leading to visual deficits in fewer than half of these individuals. The goal of chemotherapy is to preserve vision, but vision loss in NF1-associated OPG can be unpredictable. Determining which child would benefit from chemotherapy and, equally important, which child is better observed without treatment can be difficult. Unfortunately, despite frequent imaging and ophthalmologic evaluations, some children experience progressive vision loss before treatment. Indications for chemotherapy usually are based on a comprehensive, quantitative assessment of vision, but reliable vision evaluation can be challenging in young children with NF1-OPG. The ability to identify and predict impending vision loss could potentially improve management decisions and visual outcomes. To address this challenge, ophthalmologic, electrophysiologic, and imaging biomarkers of vision in NF1-OPG have been proposed. We review current recommendations for the surveillance of children at risk for NF1-OPG, outline guidelines for initiating therapy, and describe the utility of proposed biomarkers for vision.

Childhood Cancer and Brain Tumor Late Effects: Relationships with Family Burden and Survivor Psychological Outcomes.

This study examines illness-specific family burden as a mediator of the association between late effects of childhood cancer and survivors' emotional and behavioral outcomes. Childhood cancer survivors (n = 65; ages 10-17) two or more years off-treatment completed measures assessing internalizing and PTSD symptoms. Parents reported on illness-specific family burden, late effects severity, and survivor internalizing/externalizing problems. Providers documented the number of late effects. Illness-specific family burden was correlated with provider-reported late effects (r = .29, p < .05) and parent report of severe late effects (r = .56, p < .01). Results supported an indirect effect of illness-specific family burden on number of late effects and parent-reported survivor internalizing problems, p < .05. Indirect effects were not found in models predicting PTSD and externalizing problems. Illness-specific family burden is an important intervention target for reducing internalizing problems in childhood cancer survivors with late effects.

Impact of vision loss among survivors of childhood central nervous system astroglial tumors.

BACKGROUND: The impact of impaired vision on cognitive and psychosocial outcomes among long-term survivors of childhood low-grade gliomas has not been investigated previously but could inform therapeutic decision making. METHODS: Data from the Childhood Cancer Survivor Study were used to investigate psychological outcomes (measures of cognitive/emotional function) and socioeconomic outcomes (education, income, employment, marital status, and independent living) among astroglial tumor survivors grouped by 1) vision without impairment, 2) vision with impairment (including unilateral blindness, visual field deficits, and amblyopia), or 3) bilateral blindness. The effect of vision status on outcomes was examined with multivariate logistic regression with adjustments for age, sex, cranial radiation therapy, and medical comorbidities. RESULTS: Among 1233 survivors of childhood astroglial tumors 5 or more years after their diagnosis, 277 (22.5%) had visual impairment. In a multivariate analysis, survivors with bilateral blindness were more likely to be unmarried (adjusted odds ratio (OR), 4.7; 95% confidence interval [CI], 1.5-15.0), live with a caregiver (adjusted OR, 3.1; 95% CI, 1.3-7.5), and be unemployed (adjusted OR, 2.2; 95% CI, 1.1-4.5) in comparison with those without visual impairment. Bilateral blindness had no measurable effect on cognitive or emotional outcomes, and vision with impairment was not significantly associated with any psychological or socioeconomic outcomes. CONCLUSIONS: Adult survivors of childhood astroglial tumors with bilateral blindness were more likely to live unmarried and dependently and to be unemployed. Survivors with visual impairment but some remaining vision did not differ significantly with respect to psychological function and socioeconomic status from those without visual impairment. Cancer 2016;122:730-739. © 2016 American Cancer Society.

Systemic Chemotherapy and White Matter Integrity in Tracts Associated with Cognition Among Children With Neurofibromatosis Type 1.

BACKGROUND: Children with neurofibromatosis type 1 (NF1) are predisposed to both brain tumors and cognitive deficits. While changes in white matter integrity after multimodal therapy are associated with cognitive dysfunction, the effect of isolated chemotherapy in NF1 is unknown. To determine whether chemotherapy is associated with white matter microstructural changes, we examined diffusion tensor imaging (DTI) in NF1 subjects. PROCEDURE: We reviewed DTI measures in tracts associated with cognition but free from tumor in 24 children with NF1-associated optic pathway gliomas unexposed to surgery or radiation. Twelve age-matched pairs were identified based on exposure to chemotherapy. A paired t-test was used to compare fractional anisotropy (FA) in tracts of interest between subjects with and without chemotherapy exposure. RESULTS: On paired t-test, FA was significantly lower in the corpus callosum (P = 0.015) and cerebellothalamic (P = 0.038) tracts of subjects exposed to chemotherapy. There was no effect of age or time from chemotherapy on the difference between groups. In multivariable analysis, FA of these tracts was associated with chemotherapy exposure after adjusting for age, tumor location, and DTI acquisition. In longitudinal measures, FA decreased after chemotherapy exposure while FA increased with age in unexposed subjects. CONCLUSIONS: Exposure to low-intensity chemotherapy in NF1 is associated with changes in white matter microstructure in tracts associated with cognition. Future studies should determine whether these changes are associated with cognitive decline. While chemotherapy may spare cognition relative to radiation and surgery, children with NF1 exposed to chemotherapy may benefit from early cognitive testing to allow for earlier intervention.