Treatment evaluation by volumetric segmentation in pediatric optic pathway glioma: evaluation of the effect of bevacizumab on intra-tumor components.

PURPOSE: Progressive pediatric optic pathway gliomas (OPGs) are treated by diverse systemic antitumor modalities. Refined insights on the course of intra-tumoral components are limited. METHODS: We performed an exploratory study on the longitudinal volumetric course of different (intra-)tumor components by manual segmentation of MRI at the start and after 3, 6 and 12 months of bevacizumab (BVZ) treatment. RESULTS: Thirty-one patients were treated with BVZ (median 12 months, range: 2-39 months). During treatment the total tumor volume decreased with median 19.9% (range: - 62.3 to + 29.7%; n = 30) within the first 3 months, decreased 19.0% (range: - 68.8 to + 96.1%; n = 28) between start and 6 months and 27.2% (range: -73.4 to + 36.0%; n = 21) between start and 12 months. Intra-tumoral cysts were present in 12 OPGs, all showed a decrease of volume during treatment. The relative contrast enhanced volume of NF1 associated OPG (n = 11) showed an significant reduction compared to OPG with a KIAA1549-BRAF fusion (p < 0.01). Three OPGs progressed during treatment, but were not preceded by an increase of relative contrast enhancement. CONCLUSION: Treatment with BVZ of progressive pediatric OPGs leads to a decrease of both total tumor volume and cystic volume for the majority of OPGs with emphasis on the first three months. NF1 and KIAA1549-BRAF fusion related OPGs showed a different (early) treatment effect regarding the tumor enhancing component on MRI, which did not correlate with tumor volume changes. Future research is necessary to further evaluate these findings and its relevance to clinical outcome parameters.

Dose-dependent seizure control with MEK inhibitor therapy for progressive glioma in a child with neurofibromatosis type 1.

BACKGROUND: Low-grade gliomas (LGGs) occurring in children can result in many different neurologic complications, including seizures. MEK inhibitors are increasingly being used to treat LGG, but their effect on associated neurologic symptoms has not been established. RESULTS: Here, we report a patient with neurofibromatosis type 1 (NF1), medically refractory epilepsy (MRE), and an extensive optic pathway glioma (OPG) who developed dose-dependent seizure control while being treated with selumetinib. Seizure frequency rebounded after dose reduction for cardiac toxicity, then improved, and finally ceased after restarting full dosing, allowing confidence in the cause of improvement. CONCLUSION: Selumetinib may have promise in epilepsy management in other children with NF1 or LGG.

Early radiotherapy preserves vision in sporadic optic pathway glioma.

BACKGROUND: Sporadic optic pathway/hypothalamic gliomas represent a unique entity within pediatric low-grade glioma. Despite favorable survival, location makes treatment difficult and local progression debilitating. This study is a longitudinal assessment of visual acuity (VA) among children treated within the last 2 decades. METHODS: Clinical characteristics were abstracted for patients treated from 2000 to 2018 at Texas Children's Cancer Center in Houston. Ophthalmologic data taken at 3- to 6-month intervals were examined with age-appropriate VA metrics converted to the LogMAR (logarithm of the minimum angle of resolution) scale. Kaplan-Meier blindness-free survival (BFS) curves, calculated as time-to-bilateral functional blindness (LogMAR ≥0.8 in both eyes), were calculated for patients receiving early radiation therapy (RT; upfront or as first-line salvage treatment) or chemotherapy (CT) and evaluated using the log-rank test. RESULTS: Thirty-eight patients with a median follow-up of 8.5 years (range, 2-17 years) were identified. Median age at diagnosis was 3 years (interquartile range, <1-6 years). Early RT was administered in 11 patients (29%). Twenty-seven patients (71%) were treated primarily with CT, initiated at a median age of 3.5 years (range, <1-11 years). Eight patients in the CT group did eventually require RT secondary to VA loss and following multiple lines of CT. Median age at RT for all patients was 11 years (range, 3-17 years). BFS rates were 81% at 5 years and 60% at 8 years for CT and 100% at 5 and 8 years for early RT (P = .017). CONCLUSIONS: In a contemporary cohort, early RT, defined as initial or first-line salvage therapy, was found to have superior BFS for appropriately selected patients with sporadic optic pathway/hypothalamic gliomas. LAY SUMMARY: Children with low-grade brain tumors of the optic pathway generally have excellent long-term survival; however, given the location of these tumors, there can commonly be threatened vision if the tumor grows. Although radiation is generally deferred in children on the basis of legitimate concerns regarding the effects on the developing brain, it may represent a vision-preserving therapy for well-selected older patients.

Visual outcomes following everolimus targeted therapy for neurofibromatosis type 1-associated optic pathway gliomas in children.

Data for visual acuity (VA) after treatment of neurofibromatosis type 1-associated optic pathway gliomas (NF1-OPGs) are limited. We retrospectively collected VA, converted to logMAR, before and after targeted therapy with everolimus for NF1-OPG, and compared to radiologic outcomes (14/18 with NF1-OPG, 25 eyes [three without quantifiable vision]). Upon completion of treatment, VA was stable in 19 eyes, improved in four eyes, and worsened in two eyes; visual and radiologic outcomes were discordant. In summary, the majority of children with NF1-OPG exhibited stabilization of their VA after everolimus treatment. A larger, prospective study will help delineate visual outcomes after targeted therapy.

Bevacizumab for optic pathway glioma with worsening visual field in absence of imaging progression: 2 case reports and literature review.

Children with optic pathway gliomas (OPGs) frequently suffer from problems of visual function resulting from tumors. Previous reports showed that bevacizumab improved visual function in patients with OPG via tumor response to treatment. In these two case reports, we show that bevacizumab improved visual field without tumor response as seen in imaging. Both, a 10-year-old girl and a 6-year-old boy, had previous history of treatment with platinum-based chemotherapy. They had visual deterioration without tumor progression on MR imaging. Bevacizumab effectively and immediately improved visual field in both patients without imaging response of OPG. We emphasize that bevacizumab should be considered for patients with OPGs having visual deterioration without tumor progression.

Comparison of multi-shot and single shot echo-planar diffusion tensor techniques for the optic pathway in patients with neurofibromatosis type 1.

PURPOSE: Diffusion tensor imaging (DTI) may be helpful in assessing optic pathway integrity as a marker for treatment in neurofibromatosis type 1 (NF1) patients with optic gliomas (OG). However, susceptibility artifacts are common in typical single-shot echo planar imaging (ssDTI). A readout-segmented multi-shot EPI technique (rsDTI) was utilized to minimize susceptibility distortions of the skull base and improve quantitative metrics. METHODS: Healthy controls, children with NF1 without OG, and NF1 with OG ± visual symptoms were included. All subjects were scanned with both rsDTI and ssDTI sequences sequentially. Diffusion metrics and deterministic fiber tracking were calculated. Tract count, volume, and length were also compared by a two-factor mixed ANOVA. RESULTS: Five healthy controls, 7 NF1 children without OG, and 12 NF1 children with OG were imaged. Six OG patients had visual symptoms. Four subjects had no detectable optic pathway fibers on ssDTI due to susceptibility, for which rsDTI was able to delineate. Tract count (p < 0.001), tract volume (p < 0.001), and FA (P < 0.001) were significantly higher for rsDTI versus ssDTI for all subjects. MD (p < 0.001) and RD (p < 0.001) were significantly lower for rsDTI vs ssDTI. Finally, MD, AD, and RD had a significantly lower difference in NF1 children with visual symptoms compared to NF1 children without visual symptoms only on ssDTI scans. CONCLUSION: DTI with readout-segmented multi-shot EPI technique can better visualize the optic pathway and allow more confident measurements of anisotropy in NF1 patients. This is shown by a significant increase in FA, tract count, and volume with rsDTI versus ssDTI.

Current and emerging treatment strategies for children with progressive chiasmatic-hypothalamic glioma diagnosed as infants: a web-based survey.

Treatment of infant hypothalamic chiasmatic glioma (iCHG) is challenging, about 30% of the children progress during chemotherapy. Despite subsequent treatments the 5 year overall-survival rate is only 70%. This study investigates treatment strategies currently applied for progressive iCHG. A web-based questionnaire was sent out to the members of the SIOPE Brain Tumour Group asking for current second and third line strategies at progression during and after the end of first line therapy. The questionnaire was answered by 47 paediatric oncologists from 15 countries. iCHG progressing during first line therapy with carboplatin-vincristine would be considered for treatment with alternative chemotherapy by 17 (36%) and with surgery plus chemotherapy by 27 respondents (58%). Components suggested for second line were vinblastine (62%), cisplatin (34%) and cyclophosphamide (26%). For third line therapy bevacizumab (BVZ) was considered as suitable by respondents in 53% (often with irinotecan 40%) and vinblastine by 34% respectively. Experience with BVZ in CHG is shown by 53% of respondents regarding at least 95 patients (median treated 1-5 patients per respondent at any age) with a median BVZ administration over 12 months. Effectiveness was reported varying between stable disease and regression while complications were rarely stated (proteinuria, hypertension, bleeding). BVZ would be available to 85% of respondents as therapeutic option for iCHG patients. Multiple anti-neoplastic drug regimens are applied for progressive iCHG, partly considered in combination with surgery if safely feasible. BVZ is commonly used at a satisfactory level in third line, mainly combined with irinotecan.

Marked functional recovery and imaging response of refractory optic pathway glioma to BRAFV600E inhibitor therapy: a report of two cases.

BACKGROUND: Despite appropriate therapeutic interventions, progressive optic pathway glioma (OPG) in children may result in loss of vision and other neurologic morbidities. Molecularly targeted therapy against the MAP kinase pathway holds promise in improving outcomes while resulting in lower treatment-related toxicities. We report two children with refractory OPG who had a substantial and early reversal of their neurologic deficits and an impressive imaging response of their tumor to BRAFV600E inhibition therapy. METHODS: Two children with OPG (BRAFV600E-mutated pilocytic astrocytoma) who did not respond to at least one frontline therapy were treated with the oral BRAFV600E inhibitor vemurafenib. RESULTS: Both children had substantial visual compromise before start of therapy, with one child additionally having motor deficits. Both had an early improvement in their vision, and the second child showed a demonstrable improvement in motor weakness. This was accompanied by a decrease in tumor size, which was sustained at 6 months from therapy. Neither child had significant toxicities except for mild skin sensitivity to vemurafenib. CONCLUSIONS: BRAFV600E inhibitor therapy can potentially reverse visual and neurologic decline associated with progressive OPG. The clinico-radiologic response appears to be prompt and marked. Ongoing clinical trials using BRAFV600E inhibitors can help confirm these early promising findings.

Nerve growth factor improves visual loss in childhood optic gliomas: a randomized, double-blind, phase II clinical trial.

Paediatric optic pathway gliomas are low-grade brain tumours characterized by slow progression and invalidating visual loss. Presently there is no strategy to prevent visual loss in this kind of tumour. This study evaluated the effects of nerve growth factor administration in protecting visual function in patients with optic pathway glioma-related visual impairment. A prospective randomized double-blind phase II clinical trial was conducted in 18 optic pathway glioma patients, aged from 2 to 23 years, with stable disease and severe visual loss. Ten patients were randomly assigned to receive a single 10-day course of 0.5 mg murine nerve growth factor as eye drops, while eight patients received placebo. All patients were evaluated before and after treatment, testing visual acuity, visual field, visual-evoked potentials, optic coherence tomography, electroretinographic photopic negative response, and magnetic resonance imaging. Post-treatment evaluations were repeated at 15, 30, 90, and 180 days Brain magnetic resonance imaging was performed at baseline and at 180 days. Treatment with nerve growth factor led to statistically significant improvements in objective electrophysiological parameters (electroretinographic photopic negative response amplitude at 180 days and visual-evoked potentials at 30 days), which were not observed in placebo-treated patients. Furthermore, in patients in whom visual fields could still be measured, visual field worsening was only observed in placebo-treated cases, while three of four nerve growth factor-treated subjects showed significant visual field enlargement. This corresponded to improved visually guided behaviour, as reported by the patients and/or the caregivers. There was no evidence of side effects related to nerve growth factor treatment. Nerve growth factor eye drop administration appears a safe, easy and effective strategy for the treatment of visual loss associated with optic pathway gliomas.

Optic pathway glioma in children: 10 years of experience in a single institution.

Optic pathway glioma (OPG) is a rare brain tumor that occurs more commonly during early childhood and is frequently associated with neurofibromatosis type 1 (NF1). In this study, our aim was to describe the characteristics, management, and outcome of patients with OPG. We retrospectively analyzed the clinical charts of all children diagnosed with OPG at our institution from 2003 to 2013. Twenty children (11 boys and 9 girls, median age: 5 and 3/12 years; NF1: 15/20) were diagnosed with OPG. The diagnosis was based on magnetic resonance imaging (MRI) findings. A biopsy was useful in 3 patients. The main reason for seeking medical advice was decreased vision (7/20 patients), whereas in 10/20 patients, the diagnosis was established during the routine follow-up for their NF1. Fifteen patients demonstrated MRI findings of optic nerve involvement and/or chiasmal tumor, whereas in 5 children, postchiasmal structures were also involved. Sixteen patients (16/20) received carboplatin-based regimens, whereas 4/20 patients were only under close observation. Six patients showed deterioration of visual acuity and/or imaging findings at the end of treatment and/or during their follow-up. Three of them (3/6) underwent tumor resection, whereas 1 (1/6) received radiation treatment. None of our patients had total blindness from both eyes. Half of our patients were diagnosed during follow-up for their NF1, the incidence of which was high in our group. Our data suggest that chemotherapy helps in the preservation of vision in the majority of children.

Long-term visual outcome after chemotherapy for optic pathway glioma in children: Site and age are strongly predictive.

BACKGROUND: Optic pathway gliomas (OPGs) are commonly noted in pediatric oncology services. Radiotherapy is effective at controlling tumors, but has many undesirable late effects, especially in patients with neurofibromatosis. Chemotherapy is commonly used to preserve vision and delay or eliminate the need for radiotherapy. Despite visual threat being a common reason to initiate chemotherapy in patients with OPG, reports of visual outcome after chemotherapy are not common and reports of long-term visual outcome are even scarcer. METHODS: In a single institution, all patients with OPG who had received chemotherapy or radiotherapy between 1996 and 2013 were identified from hospital databases. Visual, treatment, and radiological data were recorded. Categorized visual acuity was the primary outcome measure. RESULTS: Of 43 patients identified, visual data were available for 42 patients. Approximately 14% of patients experienced an improvement in visual acuity during therapy, 9% of patients experienced a deterioration, and the remainder were stable. At a mean follow-up of 78 months, 26% of patients were legally blind. Children aged <2 years and patients with a chiasmatic/hypothalamic tumor site were overrepresented in this category. An intraconal location was predictive of poor visual outcome for that eye but was unilateral with normal vision in the contralateral eye. CONCLUSIONS: Risk factors for long-term visual deterioration are young age, chiasmatic/hypothalamic tumor site, and intraconal tumor site for the involved eye. The most common visual outcome for children with OPG after treatment with chemotherapy is stability. This stability is maintained over the long term for >90% of children without these risk factors.

Single agent vinorelbine in pediatric patients with progressive optic pathway glioma.

The management of progressive unresectable low-grade glioma remains controversial. Treatment options have included radiotherapy, and more recently chemotherapy, usually following an initial period of observation. Within this context, we evaluated vinorelbine, a semi-synthetic vinca alkaloid that has shown evidence of activity against glioma. From July 2007 an institutional protocol with vinorelbine (30 mg/m(2) days 0, 8, 22) for a total of 18 cycles, has been conducted at IOP/GRAACC/UNIFESP for children with optic pathway glioma (OPG). The main objectives were clinical and radiological response, as well as toxicity profile. Twenty-three patients with progressive OPG with a mean age of 69 months (4-179) were enrolled. Three patients had a diagnosis of neurofibromatosis type 1. Twenty-two patients were assessable for response with an overall objective response rate of 63 %, with eight patients showing stable disease. The most important toxicity was hematologic (grade III/IV neutropenia) observed in four patients. Gastrointestinal toxicity (grade I/II vomiting) was observed in seven patients and only 1 patient showed grade I peripheral neuropathy. The median progression-free survival (PFS) was 33 months (6.9-69) with a 3 and 5 year PFS of 64 ± 19 and 37 ± 20 %, respectively, for an overall 3 and 5 year-survival of 95 ± 10 %. This study suggests that vinorelbine may be an interesting option for pediatric low-grade gliomas, showing low toxicity profile and providing a good quality of life for patients with such chronic disease.

The effect of chemotherapy on optic pathway gliomas and their sub-components: A volumetric MR analysis study.

BACKGROUND: Optic pathway gliomas (OPG) represent 5% of pediatric brain tumors and compose a major therapeutic dilemma to the treating physicians. While chemotherapy is widely used for these tumors, our ability to predict radiological response is still lacking. In this study, we use volumetric imaging to examine in detail the long-term effect of chemotherapy on the tumor as well as its various sub-components. PROCEDURE: The tumors of 15 patients with OPG, treated with chemotherapy, were longitudinally measured using our novel, previously described volumetric method. Patients were treated with up to five lines of chemotherapy. Sufficient follow-up imaging data, and patient's numbers, allowed for analysis of two treatment lines. Volumetric measurements of the tumors were segmented into solid-non-enhancing, solid-enhancing, and cystic components. Outcome analysis was done per specific treatment line and for the overall follow-up period. RESULTS: An average reduction of 9.7% (±23%) in the gross-total-solid volume (GTSV) was noted following treatment with vincristine and carboplatin. The cystic component grew under therapy by an average of 12.6% (±39%). When measured over the course of the whole study period, the cystic component grew by an average of 35% (±100%) and the GTSV increased by 12% (±35%). CONCLUSION: Initial treatment with vincristine and carboplatin seems to have a minimal initial effect, mostly on the solid components. The cystic component in itself seems to be unaffected by chemotherapy, and contributes to the subsequent growth of the total volume. During the overall treatment period, both solid and cystic components grew regardless of combined treatment methods.

Optic glioma and precocious puberty in a girl with neurofibromatosis type 1 carrying an R681X mutation of NF1: case report and review of the literature.

BACKGROUND: Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder with an extremely variable phenotype. In childhood NF1 can be associated with optic glioma and central precocious puberty; the latter is more common when the optic chiasm is affected. The mutational spectrum of the NF1 gene is wide and complex; R681X is a rare severe mutation of the NF1 gene known to cause truncation of neurofibromin, with only ten reported cases in the literature so far. CASE PRESENTATION: We describe a girl with NF1 associated with early central precocious puberty appearing at 2.5 years of age and optic glioma affecting the optic chiasm as seen on magnetic resonance imaging (MRI). Genetic analysis confirmed the presence of R681X. Therapy with a gonadotropin-releasing hormone agonist was instituted with good response to therapy. The lesions on MRI were stable and no significant vision impairment was present during the 6 years of follow-up. CONCLUSION: Of the ten reported cases of NF1 due to R681X, one has presented with optic glioma and none with precocious puberty. Thus, to our knowledge, this is the first reported case of this mutation presenting with precocious puberty. We believe that this is a contribution to the few reports on the phenotype of this mutation and to the future elucidation of genotype-phenotype correlations of this disease.

Immune hemolytic anemia with drug-induced antibodies to carboplatin and vincristine in a pediatric patient with an optic pathway glioma.

BACKGROUND: Drug-induced immune hemolytic anemia (DIIHA) is a rare, but important condition requiring specialized laboratory testing for diagnosis. We report a case of DIIHA with antibodies against carboplatin and vincristine (VCR) in a child with an optic pathway glioma. Platinum-based drugs are established to cause DIIHA; to our knowledge, this is the first report implicating VCR. STUDY DESIGN AND METHODS: A 35-month-old girl with an optic pathway glioma developed hemolytic anemia while receiving carboplatin and VCR. Specialized blood bank testing was performed to determine the presence of drug-dependent antibodies and thus DIIHA. RESULTS: Initial direct antiglobulin test (DAT) was negative. A repeat DAT 3 days later was positive, 3+ with polyspecific-antiglobulin sera, weak+ with anti-immunoglobulin (Ig)G, and 2+ with anti-C3d. An eluate from the DAT-positive red blood cells (RBCs) was nonreactive. The patient's serum reacted without specificity to all RBC tested using papain-IgG-antiglobulin test (AGT) and polyethylene glycol-IgG-AGT. No alloantibodies to common RBC antigens were detected. When the serum was evaluated for the presence of drug-specific antibody, reactivity was shown with VCR and carboplatin using the drug addition solution method, but only with carboplatin using the drug-coating method. CONCLUSION: The patient developed hemolytic anemia during chemotherapy. Initial detection of a panagglutinin suggested a warm-type autoimmune process. However, since DIIHA could not be excluded, chemotherapy was discontinued and further work-up was initiated. The findings confirmed the presence of antibodies to carboplatin and VCR. This case highlights the importance for clinicians to maintain a high index of suspicion for DIIHA in patients with unexplained hemolysis and the importance of specialized serologic testing.

Visual acuity of children treated with chemotherapy for optic pathway gliomas.

BACKGROUND: Chemotherapy is the most common primary treatment modality for pediatric optic pathway gliomas (OPGs). Due to the risk of severe visual impairment, visual acuity (VA) has become a clinical parameter of fundamental importance for children with OPGs. Despite this reality, most studies omit crucial information necessary for analysis of the effect of chemotherapy on VA in patients with cerebral gliomas. The principal goal of this study was to determine the immediate and long-term visual outcome of children treated first with chemotherapy for OPGs. PROCEDURE: Retrospective, non-comparative, case series of children with OPGs treated initially with chemotherapy. VA was measured prior to chemotherapy, directly following chemotherapy, as well as at last follow-up. RESULTS: Seven children (14 eyes) were positive for the neurofibromatosis type-1 (NF1) mutation and 10 children (20 eyes) were without the NF1 mutation (sporadic). Three deaths, all in the sporadic cohort, occurred as a result of their OPG. Median follow-up time of survivors was 10.54 ± 4.36 (SD) years. Both NF1 mutation positive and sporadic cohorts had deterioration in VA over time; however, deterioration was only statistically significant in the sporadic population. The percentage of eyes with vision weaker than 20/200 prior to chemotherapy, directly following chemotherapy and at last follow-up grew from 18% to 24% to 38%, respectively. CONCLUSIONS: In both NF1 mutant and sporadic OPGs, VA deteriorated directly following chemotherapy as well as at long-term follow-up. Despite chemotherapy, eyes with severe functional impairment gradually increased over time.

Low-dose cisplatin-etoposide regimen for patients with optic pathway glioma: a report of four cases and literature review.

Optic pathway gliomas (OPGs) account for 5% of all childhood brain tumors. For years it has been discussed which was the best method of examining tumor progression when the magnetic resonance imaging (MRI) scan does not change. The role of chemotherapy in their treatment still remains controversial. We treated four consecutive patients affected by progressive OPG with lower cumulative doses of cisplatin/etoposide. The extension of disease was assessed by brain MRI scan. A complete ophthalmologic examination was performed. Ototoxicity was monitored. Our OPG patients had reduced visual acuity (VA) and/or visual field (VF) regardless of the MRI evaluation. All patients showed rapid visual recovery with improvement both in VA and in VF. At the time of writing, after a median follow-up of 34 months, all patients were alive and free from disease progression. Our results confirm the effectiveness and the low-toxicity profile of the cisplatin/etoposide regimen for treatment of children affected by OPG. We suggest that VA and VF can be considered as the most accurate parameters for defining the start of chemotherapy and tumor response.

Antiseizure effect of MEK inhibitor in a child with neurofibromatosis type 1-Developmental and epileptic encephalopathy and optic pathway glioma.

BACKGROUND: Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder due to a mutation in NF1 gene, resulting in phenotypically heterogeneous systemic manifestations. Patients with NF1 are prone to develop neoplasms of the central nervous system (CNS) and are particularly at risk for optic pathway gliomas (OPG). Epilepsy is another recognized neurologic complication in patients with NF1, with a prevalence estimated between 4% and 14%. Several case reports and early phase clinical trials have demonstrated that the mitogen-activated protein kinase inhibitors (MEKi) are effective in NF1-low-grade gliomas (LGGs), but their influence on seizure activity in humans has not been established. CASE STUDY: Here, we report a patient with NF1 and developmental and epileptic encephalopathy (DEE) harboring pharmacoresistant tonic seizures, and progressive optic pathway glioma (OPG). By using a MEKi therapy for her OPG, we observed an end to epileptic seizures as well as a significant improvement of interictal EEG abnormalities, despite a lack of tumor reduction. CONCLUSION: MEK inhibitor therapy should be considered for patients with NF1 and refractory epilepsy.

NF1 mutation-driven neuronal hyperexcitability sets a threshold for tumorigenesis and therapeutic targeting of murine optic glioma.

BACKGROUND: With the recognition that noncancerous cells function as critical regulators of brain tumor growth, we recently demonstrated that neurons drive low-grade glioma initiation and progression. Using mouse models of neurofibromatosis type 1 (NF1)-associated optic pathway glioma (OPG), we showed that Nf1 mutation induces neuronal hyperexcitability and midkine expression, which activates an immune axis to support tumor growth, such that high-dose lamotrigine treatment reduces Nf1-OPG proliferation. Herein, we execute a series of complementary experiments to address several key knowledge gaps relevant to future clinical translation. METHODS: We leverage a collection of Nf1-mutant mice that spontaneously develop OPGs to alter both germline and retinal neuron-specific midkine expression. Nf1-mutant mice harboring several different NF1 patient-derived germline mutations were employed to evaluate neuronal excitability and midkine expression. Two distinct Nf1-OPG preclinical mouse models were used to assess lamotrigine effects on tumor progression and growth in vivo. RESULTS: We establish that neuronal midkine is both necessary and sufficient for Nf1-OPG growth, demonstrating an obligate relationship between germline Nf1 mutation, neuronal excitability, midkine production, and Nf1-OPG proliferation. We show anti-epileptic drug (lamotrigine) specificity in suppressing neuronal midkine production. Relevant to clinical translation, lamotrigine prevents Nf1-OPG progression and suppresses the growth of existing tumors for months following drug cessation. Importantly, lamotrigine abrogates tumor growth in two Nf1-OPG strains using pediatric epilepsy clinical dosing. CONCLUSIONS: Together, these findings establish midkine and neuronal hyperexcitability as targetable drivers of Nf1-OPG growth and support the use of lamotrigine as a potential chemoprevention or chemotherapy agent for children with NF1-OPG.

Long-term response in high-grade optic glioma treated with medically induced hypothyroidism and carboplatin: a case report and review of the literature.

Glioblastoma multiforme (GBM) is the most malignant and frequent brain tumor, with an aggressive growth pattern and poor prognosis despite best treatment modalities. Long-term survival of patients with GBM is rare. Optic glioma represents 0.6-1.2% of all brain tumors. Unlike low-grade optic gliomas in children, optic gliomas in adults are highly aggressive and death usually occurs in less than a year. Prolonged progression-free survival and survival rates have been reported in association with induced hypothyroidism in two clinical trials for recurrent GBM. We present the clinical, radiological, and pathological findings in a patient with inoperable GBM of the optic chiasm. Following failure of initial, standard radiation and temozolomide therapy, chemical hypothyroidism was induced using the antithyroid thioamide, propylthiouracil, followed by carboplatin chemotherapy. Initial thyroid stimulating hormone, free T4, and free T3 analysis was carried out and then monthly. This patient responded rapidly to treatment (clinically and with tumor regression within 4 weeks) on two separate occasions with an extended remission period (2.5 years) and prolonged overall survival (4.5 years). We report the successful long-term tumor response to medically induced chemical hypothyroidism in conjunction with carboplatinum chemotherapy of an adult patient with grade IV GBM of the optic chiasm. These clinical observations find mechanistic support from the recent identification of potent mitogenic actions of the thyroid hormone, L-thyroxine, in malignant glioma through binding to a cognate thyroid hormone receptor on the αvß3 integrin. Approaches to block its activity are now explored in preclinical studies.