Resistance, rebound, and recurrence regrowth patterns in pediatric low-grade glioma treated by MAPK inhibition: A modified Delphi approach to build international consensus-based definitions-International Pediatric Low-Grade Glioma Coalition.

Pediatric low-grade glioma (pLGG) is the most common childhood brain tumor group. The natural history, when curative resection is not possible, is one of a chronic disease with periods of tumor stability and episodes of tumor progression. While there is a high overall survival rate, many patients experience significant and potentially lifelong morbidities. The majority of pLGGs have an underlying activation of the RAS/MAPK pathway due to mutational events, leading to the use of molecularly targeted therapies in clinical trials, with recent regulatory approval for the combination of BRAF and MEK inhibition for BRAFV600E mutated pLGG. Despite encouraging activity, tumor regrowth can occur during therapy due to drug resistance, off treatment as tumor recurrence, or as reported in some patients as a rapid rebound growth within 3 months of discontinuing targeted therapy. Definitions of these patterns of regrowth have not been well described in pLGG. For this reason, the International Pediatric Low-Grade Glioma Coalition, a global group of physicians and scientists, formed the Resistance, Rebound, and Recurrence (R3) working group to study resistance, rebound, and recurrence. A modified Delphi approach was undertaken to produce consensus-based definitions and recommendations for regrowth patterns in pLGG with specific reference to targeted therapies.

Consensus framework for conducting phase I/II clinical trials for children, adolescents, and young adults with pediatric low-grade glioma: Guidelines established by the International Pediatric Low-Grade Glioma Coalition Clinical Trial Working Group.

Within the last few decades, we have witnessed tremendous advancements in the study of pediatric low-grade gliomas (pLGG), leading to a much-improved understanding of their molecular underpinnings. Consequently, we have achieved successful milestones in developing and implementing targeted therapeutic agents for treating these tumors. However, the community continues to face many unknowns when it comes to the most effective clinical implementation of these novel targeted inhibitors or combinations thereof. Questions encompassing optimal dosing strategies, treatment duration, methods for assessing clinical efficacy, and the identification of predictive biomarkers remain unresolved. Here, we offer the consensus of the international pLGG coalition (iPLGGc) clinical trial working group on these important topics and comment on clinical trial design and endpoint rationale. Throughout, we seek to standardize the global approach to early clinical trials (phase I and II) for pLGG, leading to more consistently interpretable results as well as enhancing the pace of novel therapy development and encouraging an increased focus on functional endpoints as well and quality of life for children faced with this disease.

Phase I trial of panobinostat in children with diffuse intrinsic pontine glioma: A report from the Pediatric Brain Tumor Consortium (PBTC-047).

BACKGROUND: Diffuse intrinsic pontine glioma (DIPG) is a lethal childhood cancer with median survival of less than 1 year. Panobinostat is an oral multihistone deacetylase inhibitor with preclinical activity in DIPG models. Study objectives were to determine safety, tolerability, maximum tolerated dose (MTD), toxicity profile, and pharmacokinetics of panobinostat in children with DIPG. PATIENTS AND METHODS: In stratum 1, panobinostat was administered 3 days per week for 3 weeks on, 1 week off to children with progressive DIPG, with dose escalation following a two-stage continual reassessment method. After this MTD was determined, the study was amended to evaluate the MTD in children with nonprogressive DIPG/Diffuse midline glioma (DMG) (stratum 2) on an alternate schedule, 3 days a week every other week in an effort to escalate the dose. RESULTS: For stratum 1, 19 subjects enrolled with 17/19 evaluable for dose-finding. The MTD was 10 mg/m2/dose. Dose-limiting toxicities included thrombocytopenia and neutropenia. Posterior reversible encephalopathy syndrome was reported in 1 patient. For stratum 2, 34 eligible subjects enrolled with 29/34 evaluable for dose finding. The MTD on this schedule was 22 mg/m2/dose. DLTs included thrombocytopenia, neutropenia, neutropenia with grade 4 thrombocytopenia, prolonged intolerable nausea, and increased ALT. CONCLUSIONS: The MTD of panobinostat is 10 mg/m2/dose administered 3 times per week for 3 weeks on/1 week off in children with progressive DIPG/DMG and 22 mg/m2/dose administered 3 times per week for 1 week on/1 week off when administered in a similar population preprogression. The most common toxicity for both schedules was myelosuppression.

Cardiac Function in Children and Young Adults Treated with MEK Inhibitors: A Retrospective Cohort Study.

MEK inhibitors (MEKi) have shown efficacy in pediatric low-grade glioma as well as plexiform neurofibroma. MEKi have been associated with acute cardiac dysfunction in adults. Cardiac consequences in children are unknown. We performed a single center retrospective cohort study evaluating cardiac function by echocardiography (echo) in children and young adults < 21 years receiving MEKi between October 2013 and May 2018. Blinded assessment of left ventricular function by fractional shortening (FS) and ejection fraction (EF) was performed on all available echocardiograms performed before, during, and following therapy, as well as after re-initiation of therapy. Twenty-six patients underwent MEKi therapy with echo follow-up during the study period. Twenty-four of these had complete echo data. Median follow-up was 12 months. Borderline EF (EF 53-57.9%) occurred in 12 (50%) patients; and 3 (12.5%) progressed to abnormal EF (EF < 53%). Cardiac dysfunction, when it occurred, was mild (lowest documented EF was 45%, and lowest FS was 24.4%). EF abnormalities typically fluctuated during therapy, resolved off therapy, and recurred with MEKi re-initiation. No clinical or demographic differences were detected between those who maintained normal cardiac function and those who developed borderline or overt cardiac dysfunction. Symptomatic heart failure did not occur. In this cohort of children and young adults, MEKi use was associated with a high (50%) incidence of borderline or mildly decreased left ventricular function. There was no evidence of permanent cardiac dysfunction. Further evaluation in larger prospective trials is needed.

Clinical utility of comprehensive genomic profiling in central nervous system tumors of children and young adults.

BACKGROUND: Recent large-scale genomic studies have revealed a spectrum of genetic variants associated with specific subtypes of central nervous system (CNS) tumors. The aim of this study was to determine the clinical utility of comprehensive genomic profiling of pediatric, adolescent and young adult (AYA) CNS tumors in a prospective setting, including detection of DNA sequence variants, gene fusions, copy number alterations (CNAs), and loss of heterozygosity. METHODS: OncoKids, a comprehensive DNA- and RNA-based next-generation sequencing (NGS) panel, in conjunction with chromosomal microarray analysis (CMA) was employed to detect diagnostic, prognostic, and therapeutic markers. NGS was performed on 222 specimens from 212 patients. Clinical CMA data were analyzed in parallel for 66% (146/222) of cases. RESULTS: NGS demonstrated clinically significant alterations in 66% (147/222) of cases. Diagnostic markers were identified in 62% (138/222) of cases. Prognostic information and targetable genomic alterations were identified in 22% (49/222) and 18% (41/222) of cases, respectively. Diagnostic or prognostic CNAs were revealed by CMA in 69% (101/146) of cases. Importantly, clinically significant CNAs were detected in 57% (34/60) of cases with noncontributory NGS results. Germline cancer predisposition testing was indicated for 27% (57/212) of patients. Follow-up germline testing was performed for 20 patients which confirmed a germline pathogenic/likely pathogenic variant in 9 cases: TP53 (2), NF1 (2), SMARCB1 (1), NF2 (1), MSH6 (1), PMS2 (1), and a patient with 47,XXY Klinefelter syndrome. CONCLUSIONS: Our results demonstrate the significant clinical utility of integrating genomic profiling into routine clinical testing for pediatric and AYA patients with CNS tumors.

NF106: A Neurofibromatosis Clinical Trials Consortium Phase II Trial of the MEK Inhibitor Mirdametinib (PD-0325901) in Adolescents and Adults With NF1-Related Plexiform Neurofibromas.

PURPOSE: Patients with neurofibromatosis type 1 (NF1) frequently develop plexiform neurofibromas (PNs), which can cause significant morbidity. We performed a phase II trial of the MAPK/ERK kinase inhibitor, mirdametinib (PD-0325901), in patients with NF1 and inoperable PNs. The primary objective was response rate based on volumetric magnetic resonance imaging analysis. METHODS: Inclusion criteria included age ≥ 16 years and a PN that was either progressive or causing significant morbidity. First-dose pharmacokinetics were performed. Patients completed patient-reported outcome measures. Patients received mirdametinib by mouth twice a day at 2 mg/m2/dose (maximum dose = 4 mg twice a day) in a 3-week on/1-week off sequence. Each course was 4 weeks in duration. Evaluations were performed after four courses for the first year and then after every six courses. Patients could receive a maximum of 24 total courses. RESULTS: Nineteen patients were enrolled, and all 19 received mirdametinib. The median age was 24 years (range, 16-39 years); the median baseline tumor volume was 363.8 mL (range, 3.9-5,161 mL). Eight of the 19 patients (42%) achieved a partial response of the target PN by course 12, and 10 (53%) had stable disease. One patient (5%) developed progressive disease at course 8. Significant and durable decreases were observed in pain ratings. CONCLUSION: To our knowledge, this analysis represents the first characterization of the activity and pharmacokinetics of mirdametinib in patients with NF1 and PNs and is the first published response study for MAPK/ERK kinase inhibitors in adults with NF1 and PNs. Mirdametinib given at 2 mg/m2/dose (maximum dose, 4 mg) twice daily in a 3-week on/1-week off sequence resulted in a 42% partial response rate with preliminary evidence of reduction in pain.

Pediatric Gliosarcoma With and Without Neurofibromatosis Type 1: A Whole-exome Comparison of 2 Patients.

Gliosarcoma is rare among pediatric patients and among individuals with Neurofibromatosis Type 1 (NF1). Here we compare 2 pediatric gliosarcoma patients, one of whom has NF1. We performed whole-exome sequencing, methylation, and copy number analysis on tumor and blood for both patients. Whole-exome sequencing showed higher mutational burden in the tumor of the patient without NF1. Copy number analysis showed differences in chromosomal losses/gains between the tumors. Neither tumor showed O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation. The NF1 patient survived without progression while the other expired. This is the first reported case of gliosarcoma in a child with NF1.

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.

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.

Phase II study of peginterferon alpha-2b for patients with unresectable or recurrent craniopharyngiomas: a Pediatric Brain Tumor Consortium report.

BACKGROUND: Craniopharyngiomas account for approximately 1.2-4% of all CNS tumors. They are typically treated with a combination of surgical resection and focal radiotherapy. Unfortunately, treatment can lead to permanent deleterious effects on behavior, learning, and endocrine function. METHODS: The Pediatric Brain Tumor Consortium performed a multicenter phase 2 study in children and young adults with unresectable or recurrent craniopharyngioma (PBTC-039). Between December 2013 and November 2017, nineteen patients (median age at enrollment, 13.1 y; range, 2-25 y) were enrolled in one of 2 strata: patients previously treated with surgery alone (stratum 1) or who received radiation (stratum 2). RESULTS: Eighteen eligible patients (8 male, 10 female) were treated with weekly subcutaneous pegylated interferon alpha-2b for up to 18 courses (108 wk). Therapy was well tolerated with no grade 4 or 5 toxicities. 2 of the 7 eligible patients (28.6%) in stratum 1 had a partial response, but only one response was sustained for more than 3 months. None of the 11 stratum 2 patients had an objective radiographic response, although median progression-free survival was 19.5 months. CONCLUSIONS: Pegylated interferon alpha-2b treatment, in lieu of or following radiotherapy, was well tolerated in children and young adults with recurrent craniopharyngiomas. Although objective responses were limited, progression-free survival results are encouraging, warranting further studies.

A phase II study of continuous oral mTOR inhibitor everolimus for recurrent, radiographic-progressive neurofibromatosis type 1-associated pediatric low-grade glioma: a Neurofibromatosis Clinical Trials Consortium study.

BACKGROUND: Activation of the mammalian target of rapamycin (mTOR) pathway is observed in neurofibromatosis type 1 (NF1) associated low-grade gliomas (LGGs), but agents that inhibit this pathway, including mTOR inhibitors, have not been studied in this population. We evaluate the efficacy of the orally administered mTOR inhibitor everolimus for radiographically progressive NF1-associated pediatric LGGs. METHODS: Children with radiologic-progressive, NF1-associated LGG and prior treatment with a carboplatin-containing chemotherapy were prospectively enrolled on this phase II clinical trial to receive daily everolimus. Whole blood was analyzed for everolimus and markers of phosphatidylinositol-3 kinase (PI3K)/mTOR pathway inhibition. Serial MRIs were obtained during treatment. The primary endpoint was progression-free survival at 48 weeks. RESULTS: Twenty-three participants (median age, 9.4 y; range, 3.2-21.6 y) were enrolled. All participants were initially evaluable for response; 1 patient was removed from study after development of a malignant peripheral nerve sheath tumor. Fifteen of 22 participants (68%) demonstrated a response, defined as either shrinkage (1 complete response, 2 partial response) or arrest of tumor growth (12 stable disease). Of these, 10/15 remained free of progression (median follow-up, 33 mo). All remaining 22 participants were alive at completion of therapy. Treatment was well tolerated; no patient discontinued therapy due to toxicity. Pharmacokinetic parameters and pre-dose concentrations showed substantial between-subject variability. PI3K/mTOR pathway inhibition markers demonstrating blood mononuclear cell mTOR pathway inactivation was achieved in most participants. CONCLUSION: Individuals with recurrent/progressive NF1-associated LGG demonstrate significant disease stability/shrinkage during treatment with oral everolimus with a well-tolerated toxicity profile. Everolimus is well suited for future consideration as upfront or combination therapy in this patient population.

Prognostic significance of molecular subgroups of medulloblastoma in young children receiving irradiation-sparing regimens.

PURPOSE: Irradiation-avoiding strategies have been used with relative success in the treatment of infants and young children with medulloblastoma. While advances in cancer genomics have significantly improved our understanding of the tumor biology of medulloblastoma allowing for improved prognostication and risk-stratification, the molecular subgroup-specific outcomes of infants and young children with medulloblastoma treated with irradiation-avoiding strategies remains unknown. METHODS: Molecular and clinical features of children with medulloblastoma treated with irradiation-avoiding strategies at Children's Hospital Los Angeles were analyzed. Molecular subgrouping of these patients was determined using a 31-gene TaqMan Low Density Array signature. Survival analyses were conducted based on 3 molecular subgroups (SHH, Group 3, and Group 4). RESULTS: Twenty-eight patients with medulloblastoma received irradiation-sparing regimens and were included in this analysis. Patients were divided into SHH (n = 16), Group 3 (n = 3) and Group 4 subgroups (n = 9). Subgroup specific 5-year progression-free and overall survival was 81.2% (95% CI 52.5-93.5) and 93.7% (95% CI 63.2-99.1) for SHH, 0% and 0% for Group 3 and 0% and 44.4% (95% CI 13.6-71.9) for Group 4. CONCLUSION: The majority of young children with SHH-subgroup medulloblastoma can be treated effectively with irradiation-sparing regimens. Our results support the use of chemotherapy-only strategies for upfront treatment of young children with SHH medulloblastoma, while demonstrating the urgent need for intensification/augmentation of treatment for patients with group 3/4 medulloblastoma.

Sustained response of three pediatric BRAFV600E mutated high-grade gliomas to combined BRAF and MEK inhibitor therapy.

Outcomes for children with high-grade gliomas (HGG) remain dismal despite aggressive treatment strategies. The use of targeted therapy for BRAFV600E mutated malignancies including HGG is being explored as a potentially well tolerated and effective therapeutic option. The results of adult melanoma studies demonstrating that combination therapy with BRAF inhibitors and MEK inhibitors results in prolonged survival led us to employ this treatment strategy in children with BRAFV600E mutated HGG. In this case series, we describe three pediatric patients with HGG with confirmed BRAFV600E mutation who demonstrated responses to combination therapy with dabrafenib and trametinib.

A comparative analysis of clinicopathological features and survival among early adolescents/young adults and children with low-grade glioma: a report from the Children's Oncology Group.

BACKGROUND: For several types of cancer, biological differences and outcome disparities have been documented in adolescents/young adults (AYAs, 15-39 years old) versus children. This study compared clinicopathological features and survival between younger AYAs and children with low-grade glioma (LGG), a common brain tumor among AYAs. METHODS: This was a secondary analysis of Children's Oncology Group legacy study CCG-9891/POG-9130, which enrolled participants 0-21 years of age with newly-diagnosed LGG treated with surgery alone. For analysis, participants were categorized as children (0-14 years old) or early AYAs (eAYAs, 15-21 years old) and compared on demographics, clinical presentation, tumor characteristics, surgical outcomes, progression-free survival (PFS) and overall survival (OS). RESULTS: Among 468 children and 50 eAYAs, more eAYAs presented with seizures (34.0% vs. 19.2%; p = 0.015), without other significant differences in clinicopathological features. 5-year PFS rates for children and eAYA were 80.2% (95% confidence interval [95% CI], 76.1-83.7) and 83.0% (95% CI 68.8-91.1), respectively; 5-year OS rates were 97.3% (95% CI 95.2-98.5) and 95.4% (95% CI 82.7-98.8), respectively. Multivariable analysis including all participants showed presence of residual tumor to be an independent predictor of PFS (< 1.5 cm3, hazard ratio [HR] 5.93 [95% CI 3.45-10.18]) and (≥ 1.5 cm3, HR 8.38 [95% CI 4.75-14.79]) (p < 0.001), while midline-chiasmatic location (HR 9.69 [95% CI 3.05-30.75], p < 0.001) and non-pilocytic astrocytoma histology (HR 6.77 [95% CI 2.35-19.49], p < 0.001) were independent predictors of OS. CONCLUSION: Unlike several other cancers, LGG has similar presenting features and survival for both eAYAs and children. This support continuing a unified treatment approach and enrollment of eAYAs in pediatric clinical trials for LGGs.

Prospective feasibility and safety assessment of surgical biopsy for patients with newly diagnosed diffuse intrinsic pontine glioma.

Background: Diagnosis of diffuse intrinsic pontine glioma (DIPG) has relied on imaging studies, since the appearance is pathognomonic, and surgical risk was felt to be high and unlikely to affect therapy. The DIPG Biology and Treatment Study (DIPG-BATS) reported here incorporated a surgical biopsy at presentation and stratified subjects to receive FDA-approved agents chosen on the basis of specific biologic targets. Methods: Subjects were eligible for the trial if the clinical features and imaging appearance of a newly diagnosed tumor were consistent with a DIPG. Surgical biopsies were performed after enrollment and prior to definitive treatment. All subjects were treated with conventional external beam radiotherapy with bevacizumab, and then stratified to receive bevacizumab with erlotinib or temozolomide, both agents, or neither agent, based on O6-methylguanine-DNA methyltransferase status and epidermal growth factor receptor expression. Whole-genome sequencing and RNA sequencing were performed but not used for treatment assignment. Results: Fifty-three patients were enrolled at 23 institutions, and 50 underwent biopsy. The median age was 6.4 years, with 24 male and 29 female subjects. Surgical biopsies were performed with a specified technique and no deaths were attributed to the procedure. Two subjects experienced grade 3 toxicities during the procedure (apnea, n = 1; hypertension, n = 1). One subject experienced a neurologic deficit (left hemiparesis) that did not fully recover. Of the 50 tumors biopsied, 46 provided sufficient tissue to perform the study assays (92%, two-stage exact binomial 90% CI: 83%-97%). Conclusions: Surgical biopsy of DIPGs is technically feasible, associated with acceptable risks, and can provide biologic data that can inform treatment decisions.

Phase I trial of dasatinib, lenalidomide, and temozolomide in children with relapsed or refractory central nervous system tumors.

Single agent studies targeting the tumor microenvironment in central nervous system (CNS) tumors have largely been disappointing. Combination therapies targeting various pathways and cell types may be a more effective strategy. In this phase I study, we evaluated the combination of dasatinib, lenalidomide, and temozolomide in children with relapsed or refractory primary CNS tumors. Patients 1-21 years old with relapsed or refractory CNS tumors were eligible. Starting doses of dasatinib and lenalidomide were 65 mg/m2/dose twice daily and 55 mg/m2 once daily, respectively, while temozolomide was constant at 75 mg/m2 daily. The study followed a 3 + 3 phase I design, with a 4-week dose-limiting toxicity (DLT) evaluation period. Serial peripheral blood lymphocyte subsets were evaluated in consenting patients. Fifteen patients were enrolled and thirteen were DLT-evaluable. DLTs occurred in 5 patients, including somnolence and confusion (1 patient), hypokalemia (1 patient) and thrombocytopenia (3 patients). The maximum tolerated dose for the combination was dasatinib 65 mg/m2 twice daily, lenalidomide 40 mg/m2 daily, and temozolomide 75 mg/m2 daily, for 21 days followed by 7 days rest in repeating 28-day cycles. Transient increases in natural killer effector cells and cytotoxic T-cells were seen after 1 week of treatment. One out of six response-evaluable patients showed a partial response. The combination was feasible and relatively well tolerated in this heavily pre-treated population. The most common toxicities were hematologic. Preliminary evidence of clinical benefit was seen.

Novel GOPC(FIG)-ROS1 fusion in a pediatric high-grade glioma survivor.

Pediatric high-grade glioma is a rare tumor characterized by high mortality. The authors report the first case of a high-grade glioma associated with a GOPC(FIG)-ROS1 fusion in a pediatric patient. The patient underwent gross-total resection at the age of 4 years, followed by adjuvant high-dose chemotherapy and autologous hematopoietic stem cell rescue. At 30 months after transplantation, she remains disease free.

Molecular subgroups of medulloblastoma identification using noninvasive magnetic resonance spectroscopy.

BACKGROUND: Medulloblastomas in children can be categorized into 4 molecular subgroups with differing clinical characteristics, such that subgroup determination aids in prognostication and risk-adaptive treatment strategies. Magnetic resonance spectroscopy (MRS) is a widely available, noninvasive tool that is used to determine the metabolic characteristics of tumors and provide diagnostic information without the need for tumor tissue. In this study, we investigated the hypothesis that metabolite concentrations measured by MRS would differ between molecular subgroups of medulloblastoma and allow accurate subgroup determination. METHODS: MRS was used to measure metabolites in medulloblastomas across molecular subgroups (SHH = 12, Groups 3/4 = 17, WNT = 1). Levels of 14 metabolites were analyzed to determine those that were the most discriminant for medulloblastoma subgroups in order to construct a multivariable classifier for distinguishing between combined Group 3/4 and SHH tumors. RESULTS: Medulloblastomas across molecular subgroups revealed distinct spectral features. Group 3 and Group 4 tumors demonstrated metabolic profiles with readily detectable taurine, lower levels of lipids, and high levels of creatine. SHH tumors showed prominent choline and lipid with low levels of creatine and little or no evidence of taurine. A 5-metabolite subgroup classifier inclusive of creatine, myo-inositol, taurine, aspartate, and lipid 13a was developed that could discriminate between Group 3/4 and SHH medulloblastomas with excellent accuracy (cross-validated area under the curve [AUC] = 0.88). CONCLUSIONS: The data show that medulloblastomas of Group 3/4 differ metabolically as measured using MRS when compared with SHH molecular subgroups. MRS is a useful and accurate tool to determine medulloblastoma molecular subgroups.

Tumor-associated macrophages in SHH subgroup of medulloblastomas.

PURPOSE: Medulloblastoma in children can be categorized into at least four molecular subgroups, offering the potential for targeted therapeutic approaches to reduce treatment-related morbidities. Little is known about the role of tumor microenvironment in medulloblastoma or its contribution to these molecular subgroups. Tumor microenvironment has been shown to be an important source for therapeutic targets in both adult and pediatric neoplasms. In this study, we investigated the hypothesis that expression of genes related to tumor-associated macrophages (TAM) correlates with the medulloblastoma molecular subgroups and contributes to a diagnostic signature. METHODS: Gene-expression profiling using human exon array (n = 168) was analyzed to identify medulloblastoma molecular subgroups and expression of inflammation-related genes. Expression of 45 tumor-related and inflammation-related genes was analyzed in 83 medulloblastoma samples to build a gene signature predictive of molecular subgroups. TAMs in medulloblastomas (n = 54) comprising the four molecular subgroups were assessed by immunohistochemistry (IHC). RESULTS: A 31-gene medulloblastoma subgroup classification score inclusive of TAM-related genes (CD163 and CSF1R) was developed with a misclassification rate of 2%. Tumors in the Sonic Hedgehog (SHH) subgroup had increased expression of inflammation-related genes and significantly higher infiltration of TAMs than tumors in the Group 3 or Group 4 subgroups (P < 0.0001 and P < 0.0001, respectively). IHC data revealed a strong association between location of TAMs and proliferating tumor cells. CONCLUSIONS: These data show that SHH tumors have a unique tumor microenvironment among medulloblastoma subgroups. The interactions of TAMs and SHH medulloblastoma cells may contribute to tumor growth revealing TAMs as a potential therapeutic target.