Management of sagittal synostosis in the Synostosis Research Group: baseline data and early outcomes

OBJECTIVE

Sagittal synostosis is the most common form of isolated craniosynostosis. Although some centers have reported extensive experience with this condition, most reports have focused on a single center. In 2017, the Synostosis Research Group (SynRG), a multicenter collaborative network, was formed to study craniosynostosis. Here, the authors report their early experience with treating sagittal synostosis in the network. The goals were to describe practice patterns, identify variations, and generate hypotheses for future research.

METHODS

All patients with a clinical diagnosis of isolated sagittal synostosis who presented to a SynRG center between March 1, 2017, and October 31, 2019, were included. Follow-up information through October 31, 2020, was included. Data extracted from the prospectively maintained SynRG registry included baseline parameters, surgical adjuncts and techniques, complications prior to discharge, and indications for reoperation. Data analysis was descriptive, using frequencies for categorical variables and means and medians for continuous variables.

RESULTS

Two hundred five patients had treatment for sagittal synostosis at 5 different sites. One hundred twenty-six patients were treated with strip craniectomy and 79 patients with total cranial vault remodeling. The most common strip craniectomy was wide craniectomy with parietal wedge osteotomies (44%), and the most common cranial vault remodeling procedure was total vault remodeling without forehead remodeling (63%). Preoperative mean cephalic indices (CIs) were similar between treatment groups: 0.69 for strip craniectomy and 0.68 for cranial vault remodeling. Thirteen percent of patients had other health problems. In the cranial vault cohort, 81% of patients who received tranexamic acid required a transfusion compared with 94% of patients who did not receive tranexamic acid. The rates of complication were low in all treatment groups. Five patients (2%) had an unintended reoperation. The mean change in CI was 0.09 for strip craniectomy and 0.06 for cranial vault remodeling; wide craniectomy resulted in a greater change in CI in the strip craniectomy group.

CONCLUSIONS

The baseline severity of scaphocephaly was similar across procedures and sites. Treatment methods varied, but cranial vault remodeling and strip craniectomy both resulted in satisfactory postoperative CIs. Use of tranexamic acid may reduce the need for transfusion in cranial vault cases. The wide craniectomy technique for strip craniectomy seemed to be associated with change in CI. Both findings seem amenable to testing in a randomized controlled trial.

The transcriptional landscape of Shh medulloblastoma

Sonic hedgehog medulloblastoma encompasses a clinically and molecularly diverse group of cancers of the developing central nervous system. Here, we use unbiased sequencing of the transcriptome across a large cohort of 250 tumors to reveal differences among molecular subtypes of the disease, and demonstrate the previously unappreciated importance of non-coding RNA transcripts. We identify alterations within the cAMP dependent pathway (GNAS, PRKAR1A) which converge on GLI2 activity and show that 18% of tumors have a genetic event that directly targets the abundance and/or stability of MYCN. Furthermore, we discover an extensive network of fusions in focally amplified regions encompassing GLI2, and several loss-of-function fusions in tumor suppressor genes PTCH1, SUFU and NCOR1. Molecular convergence on a subset of genes by nucleotide variants, copy number aberrations, and gene fusions highlight the key roles of specific pathways in the pathogenesis of Sonic hedgehog medulloblastoma and open up opportunities for therapeutic intervention.

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.

Predictors of fast and ultrafast shunt failure in pediatric hydrocephalus: a Hydrocephalus Clinical Research Network study

OBJECTIVE

The primary objective of this study was to use the prospective Hydrocephalus Clinical Research Network (HCRN) registry to determine clinical predictors of fast time to shunt failure (≤ 30 days from last revision) and ultrafast time to failure (≤ 7 days from last revision).

METHODS

Revisions (including those due to infection) to permanent shunt placements that occurred between April 2008 and November 2017 for patients whose entire shunt experience was recorded in the registry were analyzed. All registry data provided at the time of initial shunt placement and subsequent revision were reviewed. Key variables analyzed included etiology of hydrocephalus, age at time of initial shunt placement, presence of slit ventricles on imaging at revision, whether the ventricles were enlarged at the time of revision, and presence of prior fast failure events. Univariable and multivariable analyses were performed to find key predictors of fast and ultrafast failure events.

RESULTS

A cohort of 1030 patients with initial shunt insertions experienced a total of 1995 revisions. Of the 1978 revision events with complete records, 1216 (61.5%) shunts remained functional for more than 1 year, and 762 (38.5%) failed within 1 year of the procedure date. Of those that failed within 1 year, 423 (55.5%) failed slowly (31-365 days) and 339 (44.5%) failed fast (≤ 30 days). Of the fast failures, 131 (38.6%) were ultrafast (≤ 7 days). In the multivariable analysis specified a priori, etiology of hydrocephalus (p = 0.005) and previous failure history (p = 0.011) were independently associated with fast failure. Age at time of procedure (p = 0.042) and etiology of hydrocephalus (p = 0.004) were independently associated with ultrafast failure. These relationships in both a priori models were supported by the data-driven multivariable models as well.

CONCLUSIONS

Neither the presence of slit ventricle syndrome nor ventricular enlargement at the time of shunt failure appears to be a significant predictor of repeated, rapid shunt revisions. Age at the time of procedure, etiology of hydrocephalus, and the history of previous failure events seem to be important predictors of fast and ultrafast shunt failure. Further work is required to understand the mechanisms of these risk factors as well as mitigation strategies.

IMG-09. RESPONSE ASSESSMENT IN DIFFUSE INTRINSIC PONTINE GLIOMA (DIPG): RECOMMENDATIONS FROM THE RESPONSE ASSESSMENT IN PEDIATRIC NEURO-ONCOLOGY COMMITTEE

Optimizing the conduct of clinical trials for diffuse intrinsic pontine glioma (DIPG) involves use of consistent, objective disease assessments and standardized response criteria. The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee, an international panel of pediatric and adult neuro-oncologists, clinicians, radiologists, radiation oncologists, and neurosurgeons, was established to address unique challenges in assessing response in children with CNS tumors. A subcommittee of RAPNO was formed to specifically address response assessment in children and young adults with DIPG and to develop a consensus on recommendations for response assessment. Distinct issues related to the response assessment of DIPG include its definition and recent molecular classifications, dearth of imaging response data, the phenomena of pseudoprogression, and measuring response in the era of focal drug delivery. The committee has recommended response be assessed using magnetic resonance imaging (MRI) of brain and spine, neurologic examination, and use of supportive medication, i.e. steroids and anti-angiogenic agents. Clinical imaging standards and imaging quality control are defined. Unique recommendations for DIPG response include an eight-week response duration, a twenty-five percent decrease for partial response, and the distinction of pontine and extra-pontine response for trials that use focal drug delivery. The recommendations presented here represent an initial effort to uniformly collect and evaluate response assessment criteria; these recommendations can now be incorporated into clinical trials to assess feasibility and corroboration with patient outcomes.

LGG-04. A PHASE II RE-TREATMENT STUDY OF SELUMETINIB FOR RECURRENT OR PROGRESSIVE PEDIATRIC LOW-GRADE GLIOMA (pLGG): A PEDIATRIC BRAIN TUMOR CONSORTIUM (PBTC) STUDY

The PBTC conducted a re-treatment study (NCT01089101) evaluating selumetinib (AZD6244, ARRY-142886), a MEK I/II inhibitor, in children with recurrent/progressive pLGG. Eligible patients must have previously enrolled on PBTC-029 or PBTC-029B and progressed after coming off treatment with selumetinib. Patients must have maintained stable disease (SD) for ≥12 courses or had a sustained radiographic response (partial or complete) during their first exposure to selumetinib. Thirty-five eligible patients (median age: 13.11 years [range 7.96–25.33]) were enrolled, 57% of whom had optic pathway or hypothalamic target lesions. At the time of submission, median duration of treatment was 18 courses (range 2–48) and 21 subjects remained on therapy. Best responses reported to date are 6/35 (17%) partial response, 22/35 (63%) SD and 7/35 (20%) progressive disease with a 2-year progression-free survival of 75.7 + 8.3%, which met the design parameters for success. The most common attributable toxicities were grade 1 diarrhea, elevated AST, hypoalbuminemia, elevated CPK, maculo-papular rash, fatigue, paronychia, ALT elevation, acneiform rash and grade 2 CPK elevation. Rare grade 3 toxicities included CPK elevation (3), lymphopenia (2), paronychia (2) and ALT elevation (2). There was only one grade 4 CPK elevation. Five patients (14%) required dose reductions due to toxicity. There does not appear to be a notable difference in toxicities observed during initial selumetinib therapy versus re-treatment. In pLGG that has recurred/progressed following treatment with selumetinib, re-treatment with selumetinib appears to be effective with 80% of patients again achieving response or prolonged stable disease. Long-term follow-up is ongoing.

Surgical resource utilization after initial treatment of infant hydrocephalus: comparing ETV, early experience of ETV with choroid plexus cauterization, and shunt insertion in the Hydrocephalus Clinical Research Network

OBJECTIVE

Few studies have addressed surgical resource utilization-surgical revisions and associated hospital admission days-following shunt insertion or endoscopic third ventriculostomy (ETV) with or without choroid plexus cauterization (CPC) for CSF diversion in hydrocephalus. Study members of the Hydrocephalus Clinical Research Network (HCRN) investigated differences in surgical resource utilization between CSF diversion strategies in hydrocephalus in infants.

METHODS

Patients up to corrected age 24 months undergoing initial definitive treatment of hydrocephalus were reviewed from the prospectively maintained HCRN Core Data Project (Hydrocephalus Registry). Postoperative courses (at 1, 3, and 5 years) were studied for hydrocephalus-related surgeries (primary outcome) and hospital admission days related to surgical revision (secondary outcome). Data were summarized using descriptive statistics and compared using negative binomial regression, controlling for age, hydrocephalus etiology, and HCRN center. The study population was organized into 3 groups (ETV alone, ETV with CPC, and CSF shunt insertion) during the 1st postoperative year and 2 groups (ETV alone and CSF shunt insertion) during subsequent years due to limited long-term follow-up data.

RESULTS

Among 1090 patients, the majority underwent CSF shunt insertion (CSF shunt, 83.5%; ETV with CPC, 10.0%; and ETV alone, 6.5%). Patients undergoing ETV with CPC had a higher mean number of revision surgeries (1.2 ± 1.6) than those undergoing ETV alone (0.6 ± 0.8) or CSF shunt insertion (0.7 ± 1.3) over the 1st year after surgery (p = 0.005). At long-term follow-up, patients undergoing ETV alone experienced a nonsignificant lower mean number of revision surgeries (0.7 ± 0.9 at 3 years and 0.8 ± 1.3 at 5 years) than those undergoing CSF shunt insertion (1.1 ± 1.9 at 3 years and 1.4 ± 2.6 at 5 years) and exhibited a lower mean number of hospital admission days related to revision surgery (3.8 ± 10.3 vs 9.9 ± 27.0, p = 0.042).

CONCLUSIONS

Among initial treatment strategies for hydrocephalus, ETV with CPC yielded a higher surgical revision rate within 1 year after surgery. Patients undergoing ETV alone exhibited a nonsignificant lower mean number of surgical revisions than CSF shunt insertion at 3 and 5 years postoperatively. Additionally, the ETV-alone cohort demonstrated significantly fewer hospital admission days related to surgical management of hydrocephalus within 3 years after surgery. These findings suggest a time-dependent benefit of ETV over CSF shunt insertion regarding surgical resource utilization.

Decompressive Cranial Vault Remodeling in Osteosclerotic Robinow Syndrome

We present a novel application of endocranial burr contouring for cranial vault expansion as a surgical adjunct during decompressive craniectomy in patients with cranial osteosclerosis. A 16-year-old female with osteosclerotic Robinow syndrome complicated by slit ventricle syndrome presented with refractory intracranial hypertension following external ventricular drain placement. Symptoms included severe headaches and altered mental status. Given the severe intracranial volume restriction secondary to massive calvarial thickening (2.5 cm), the patient was taken to the operating room for urgent surgical decompression. After frontal and parietal craniectomy, burr and osteotome contouring were used to remove two-thirds of the endocranial calvarial bone flap thickness resulting in a 9% cranial vault expansion while preserving an overall normal head size. There were no immediate postoperative complications. At over 3 years postoperatively, the patient had reduced headaches, maintained adequate shunt function, and has not required further vault reconstruction.

Response assessment in diffuse intrinsic pontine glioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group

Optimising the conduct of clinical trials for diffuse intrinsic pontine glioma involves use of consistent, objective disease assessments and standardised response criteria. 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. A working group was formed specifically to address response assessment in children and young adults with diffuse intrinsic pontine glioma and to develop a consensus on recommendations for response assessment. Response should be assessed using MRI of brain and spine, neurological examination, and anti-inflammatory or antiangiogenic drugs. Clinical imaging standards are defined. As with previous consensus recommendations, these recommendations will need to be validated in prospective clinical trials.

Targeting NAD+ Biosynthesis Overcomes Panobinostat and Bortezomib-Induced Malignant Glioma Resistance

To improve therapeutic responses in patients with glioma, new combination therapies that exploit a mechanistic understanding of the inevitable emergence of drug resistance are needed. Intratumoral heterogeneity enables a low barrier to resistance in individual patients with glioma. We reasoned that targeting two or more fundamental processes that gliomas are particularly dependent upon could result in pleiotropic effects that would reduce the diversity of resistant subpopulations allowing convergence to a more robust therapeutic strategy. In contrast to the cytostatic responses observed with each drug alone, the combination of the histone deacetylase inhibitor panobinostat and the proteasome inhibitor bortezomib synergistically induced apoptosis of adult and pediatric glioma cell lines at clinically achievable doses. Resistance that developed was examined using RNA-sequencing and pharmacologic screening of resistant versus drug-naïve cells. Quinolinic acid phosphoribosyltransferase (QPRT), the rate-determining enzyme for de novo synthesis of NAD⁺ from tryptophan, exhibited particularly high differential gene expression in resistant U87 cells and protein expression in all resistant lines tested. Reducing QPRT expression reversed resistance, suggesting that QPRT is a selective and targetable dependency for the panobinostat-bortezomib resistance phenotype. Pharmacologic inhibition of either NAD⁺ biosynthesis or processes such as DNA repair that consume NAD⁺ or their simultaneous inhibition with drug combinations, specifically enhanced apoptosis in treatment-resistant cells. Concomitantly, de novo vulnerabilities to known drugs were observed. IMPLICATIONS: These data provide new insights into mechanisms of treatment resistance in gliomas, hold promise for targeting recurrent disease, and provide a potential strategy for further exploration of next-generation inhibitors.

Molecular Heterogeneity and Cellular Diversity: Implications for Precision Treatment in Medulloblastoma

Medulloblastoma, the most common pediatric malignant brain tumor, continues to have a high rate of morbidity and mortality in childhood. Recent advances in cancer genomics, single-cell sequencing, and sophisticated tumor models have revolutionized the characterization and stratification of medulloblastoma. In this review, we discuss heterogeneity associated with four major subgroups of medulloblastoma (WNT, SHH, Group 3, and Group 4) on the molecular and cellular levels, including histological features, genetic and epigenetic alterations, proteomic landscape, cell-of-origin, tumor microenvironment, and therapeutic approaches. The intratumoral molecular heterogeneity and intertumoral cellular diversity clearly underlie the divergent biology and clinical behavior of these lesions and highlight the future role of precision treatment in this devastating brain tumor in children.

Efficacy of High-Dose Chemotherapy and Three-Dimensional Conformal Radiation for Atypical Teratoid/Rhabdoid Tumor: A Report From the Children's Oncology Group Trial ACNS0333

PURPOSE

Atypical teratoid/rhabdoid tumor (AT/RT) is an aggressive, early-childhood brain tumor without standard effective treatment. To our knowledge, we conducted the first AT/RT-specific cooperative group trial, ACNS0333, to examine the efficacy and safety of intensive postoperative chemotherapy and focal radiation to treat AT/RT.

PATIENTS AND METHODS

Patients from birth to 22 years of age with AT/RT were eligible. After surgery, they received 2 courses of multiagent chemotherapy, followed by 3 courses of high-dose chemotherapy with peripheral blood stem cell rescue and involved-field radiation therapy. Timing of radiation was based on patient age and disease location and extent. Central testing of tumor and blood for SMARCB1 status was mandated. Tumor molecular subclassification was performed retrospectively. The primary analysis was event-free survival (EFS) for patients < 36 months of age compared with a cooperative groups' historical cohort. Although accrual was based on the therapeutic question, potential prognostic factors, including age, tumor location, M stage, surgical resection, order of therapy, germline status, and molecular subtype, were explored.

RESULTS

Of 65 evaluable patients, 54 were < 36 months of age. ACNS0333 therapy significantly reduced the risk of EFS events in patients < 36 months of age compared with the historical cohort (P < .0005; hazard rate, 0.43; 95% CI, 0.28 to 0.66). Four-year EFS and overall survival for the entire cohort were 37% (95% CI, 25% to 49%) and 43% (95% CI, 31% to 55%), respectively. Timing of radiation did not affect survival, and 91% of relapses occurred by 2 years from enrollment. Treatment-related deaths occurred in 4 patients.

CONCLUSION

The ACNS0333 regimen dramatically improved survival compared with historical therapies for patients with AT/RT. Clinical characteristics and molecular subgrouping suggest prognostic differences. ACNS0333 results lay a foundation on which to build future studies and incorporate testing of new therapeutic agents.

Outcomes in children undergoing posterior fossa decompression and duraplasty with and without tonsillar reduction for Chiari malformation type I and syringomyelia: a pilot prospective multicenter cohort study

OBJECTIVE

Despite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study's goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction.

METHODS

Participating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1-2 weeks, 3-6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neurosurgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx.

RESULTS

Eight clinical sites were chosen based on the results of a published questionnaire intended to remove geographic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging records were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications.

CONCLUSIONS

This study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations.

Syndromic and Systemic Diagnoses Associated With Isolated Sagittal Synostosis

Reports of systemic associations in patients with Isolated Sagittal Synostosis (ISS) are sparse. Craniofacial surgeons, and other providers, should be aware that a significant proportion of patients with ISS may have syndromic or systemic involvement. This study investigates the incidence of systemic disease and syndromic diagnosis in a cohort of patients presenting with ISS (ie, patients with sagittal synostosis without other sutural involvement).

METHODS

This study consists of a retrospective review of patients diagnosed with ISS between 2007 and 2017 at a single institution. Patients were divided according to onset (early <1 year, late >1 year) of ISS. Patient notes were examined for congenital anomalies, systemic conditions, and molecular testing. Only patients with isolated sagittal fusion-meaning, patients with sagittal synostosis and no other sutural involvement-were included.

RESULTS

Three hundred seventy-seven patients met the inclusion criteria: systemic conditions were identified in 188/377 (50%) of them. One hundred sixty-one patients with early onset (Group A), and 216 patients with late onset ISS (Group B) were identified. Systemic involvement was identified in 38% of Group A and 60% of Group B, which was statistically significant (P < 0.001). Forty-eight of 377 (13%) of patients had a syndromic diagnosis, and 79% of these were confirmed via genetic testing. Thirty-five percent of patients were diagnosed with central nervous system anomalies and 16% had craniofacial anomalies.

CONCLUSIONS

Nearly 50% of the patients initially diagnosed with ISS were found to have some form of systemic involvement. This supports affording full pediatric and genetic evaluation with molecular testing to these children.

Recurrent noncoding U1 snRNA mutations drive cryptic splicing in SHH medulloblastoma

Recurrent somatic single nucleotide variants (SNVs) in cancer are largely confined to protein coding genes, and are rare in most pediatric cancers^1–3. We report highly recurrent hotspot mutations of U1 spliceosomal small nuclear RNAs (snRNAs) in ~50% of Sonic Hedgehog medulloblastomas (Shh-MB), which were not present across other medulloblastoma subgroups. This U1-snRNA hotspot mutation (r.3a>g), was identified in <0.1% of 2,442 cancers across 36 other tumor types. Largely absent from infant Shh-MB, the mutation occurs in 97% of adults (Shhδ), and 25% of adolescents (Shhα). The U1-snRNA mutation occurs in the 5′ splice site binding region, and snRNA mutant tumors have significantly disrupted RNA splicing with an excess of 5′ cryptic splicing events. Mutant U1-snRNA mediated alternative splicing inactivates tumor suppressor genes (PTCH1), and activates oncogenes (GLI2, CCND2), represents a novel target for therapy, and constitutes a highly recurrent and tissue-specific mutation of a non-protein coding gene in cancer.

Clinical Utility of GlioSeq Next-Generation Sequencing Test in Pediatric and Young Adult Patients With Brain Tumors

Brain tumors are the leading cause of death in children. Establishing an accurate diagnosis and therapy is critical for patient management. This study evaluated the clinical utility of GlioSeq, a next-generation sequencing (NGS) assay, for the diagnosis and management of pediatric and young adult patients with brain tumors. Between May 2015 and March 2017, 142 consecutive brain tumors were tested using GlioSeq v1 and subset using GlioSeq v2. Out of 142 samples, 63% were resection specimens and 37% were small stereotactic biopsies. GlioSeq sequencing was successful in 100% and 98.6% of the cases for the detection of mutations and copy number changes, and gene fusions, respectively. Average turnaround time was 8.7 days. Clinically significant genetic alterations were detected in 95%, 66.6%, and 66.1% of high-grade gliomas, medulloblastomas, and low-grade gliomas, respectively. GlioSeq enabled molecular-based stratification in 92 (65%) cases by specific molecular subtype assignment (70, 76.1%), substantiating a neuropathologic diagnosis (18, 19.6%), and diagnostic recategorization (4, 4.3%). Fifty-seven percent of the cases harbored therapeutically actionable findings. GlioSeq NGS analysis offers rapid detection of a wide range of genetic alterations across a spectrum of pediatric brain tumors using formalin-fixed, paraffin-embedded specimens and facilitates integrated molecular-morphologic classification and personalized management of pediatric brain tumors.

Abstract 3014: Gene signatures identify quinolate phosphoribosyltransferase as a key mediator of acquired resistance to Panobinostat and Bortezomib in glioma, and NAD+ biosynthesis as a targetable pathway to reverse treatment resistance

Resistance of tumor cells to the induction of apoptosis is an important reason for the failure of anticancer treatments in patients with gliomas. Several factors working in concert have been implicated as sources of this treatment resistance; therefore, innovative therapeutic approaches that conspire to attack key tumor vulnerabilities are needed. HDAC and proteasome inhibitors are two classes of agents that have shown some benefit in the clinic, but patients often rapidly manifest intrinsic or acquired resistance mechanisms that limits their individual efficacy. We demonstrate that the combination of the HDAC inhibitor panobinostat and the proteasome inhibitor bortezomib synergistically induces apoptosis of human glioma cell lines. However, acquired resistance is observed even with this initially effective combination. To examine the mechanism of this resistance, we performed RNA sequencing and pharmacological screening of resistant compared to sensitive cells. Based on these studies, we present evidence that quinolinic acid phosphoribosyltransferase (QPRT), an enzyme catalyzes a rate determining step in de novo NAD+ biosynthesis, provides a critical adaptive survival mechanism that allows cancer cells to evade an initially effective therapeutic combination. We identified 1004 genes that had a significant change between panobinostat and bortezomib- resistant cells versus inhibitor naïve control cells. Furthermore, pathway analysis revealed that the experimental regimen significantly altered metabolic pathways. By silencing QPRT (using siRNA) we demonstrated that we can overcome resistance, thus suggesting QPRT as a crucial crossroad for cancer cell survival and as a new anticancer target. We also showed that treatment of panobinostat and bortezomib resistant cells with FK866, niraparib, selisistat, epacadostat, gemcitabine, 5-fluoruracil, and methotrexate significantly increased cell death highlighting the importance of NAD+ and folate pathway inhibitors in resensitizing the resistant cells. Together, targeting QPRT or NAD+ consuming enzymes hold promise for eliminating recurrent disease in glioma.

Citation Format: Esther P. Jane, Daniel R. Premkumar, Sameer Agnihotri, Max Myers, Ansuman Chattopadhyay, D. Lansing Taylor, Mark Schurdak, Andrew Stern, Ian F. Pollack. Gene signatures identify quinolate phosphoribosyltransferase as a key mediator of acquired resistance to Panobinostat and Bortezomib in glioma, and NAD+ biosynthesis as a targetable pathway to reverse treatment resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3014.

Selumetinib in paediatric patients with BRAF-aberrant or neurofibromatosis type 1-associated recurrent, refractory, or progressive low-grade glioma: a multicentre, phase 2 trial

BACKGROUND

Paediatric low-grade glioma is the most common CNS tumour of childhood. Although overall survival is good, disease often recurs. No single universally accepted treatment exists for these patients; however, standard cytotoxic chemotherapies are generally used. We aimed to assess the activity of selumetinib, a MEK1/2 inhibitor, in these patients.

METHODS

The Pediatric Brain Tumor Consortium performed a multicentre, phase 2 study in patients with paediatric low-grade glioma in 11 hospitals in the USA. Patients aged 3-21 years with a Lansky or Karnofsky performance score greater than 60 and the presence of recurrent, refractory, or progressive paediatric low-grade glioma after at least one standard therapy were eligible for inclusion. Patients were assigned to six unique strata according to histology, tumour location, NF1 status, and BRAF aberration status; herein, we report the results of strata 1 and 3. Stratum 1 comprised patients with WHO grade I pilocytic astrocytoma harbouring either one of the two most common BRAF aberrations (KIAA1549-BRAF fusion or the BRAF^V600E [Val600Glu] mutation). Stratum 3 comprised patients with any neurofibromatosis type 1 (NF1)-associated paediatric low-grade glioma (WHO grades I and II). Selumetinib was provided as capsules given orally at the recommended phase 2 dose of 25 mg/m² twice daily in 28-day courses for up to 26 courses. The primary endpoint was the proportion of patients with a stratum-specific objective response (partial response or complete response), as assessed by the local site and sustained for at least 8 weeks. All responses were reviewed centrally. All eligible patients who initiated treatment were evaluable for the activity and toxicity analyses. Although the trial is ongoing in other strata, enrolment and planned follow-up is complete for strata 1 and 3. This trial is registered with ClinicalTrials.gov, number NCT01089101.

FINDINGS

Between July 25, 2013, and June 12, 2015, 25 eligible and evaluable patients were accrued to stratum 1, and between Aug 28, 2013, and June 25, 2015, 25 eligible and evaluable patients were accrued to stratum 3. In stratum 1, nine (36% [95% CI 18-57]) of 25 patients achieved a sustained partial response. The median follow-up for the 11 patients who had not had a progression event by Aug 9, 2018, was 36·40 months (IQR 21·72-45·59). In stratum 3, ten (40% [21-61]) of 25 patients achieved a sustained partial response; median follow-up was 48·60 months (IQR 39·14-51·31) for the 17 patients without a progression event by Aug 9, 2018. The most frequent grade 3 or worse adverse events were elevated creatine phosphokinase (five [10%]) and maculopapular rash (five [10%]). No treatment-realted deaths were reported.

INTERPRETATION

Selumetinib is active in recurrent, refractory, or progressive pilocytic astrocytoma harbouring common BRAF aberrations and NF1-associated paediatric low-grade glioma. These results show that selumetinib could be an alternative to standard chemotherapy for these subgroups of patients, and have directly led to the development of two Children's Oncology Group phase 3 studies comparing standard chemotherapy to selumetinib in patients with newly diagnosed paediatric low-grade glioma both with and without NF1.

FUNDING

National Cancer Institute Cancer Therapy Evaluation Program, the American Lebanese Syrian Associated Charities, and AstraZeneca.

RASopathy in Patients With Isolated Sagittal Synostosis

RASopathy is caused by dysfunction in the MAPK pathway, and include syndromes like Noonan syndrome (NS), NS with multiple lentigines (formerly known as Leopard syndrome), cardiofaciocutaneous (CFC), Legius syndrome, capillary malformation–arteriovenous malformation, neurofibromatosis type 1, and Costello syndrome. When counted together, RASopathies affect 1/1000 live births, and are characterized by cardiovascular manifestations, short stature, developmental delay, renal, urogenital, skin/skeletal abnormalities, and dysmorphic appearance. NS—one of the most common RASopathies—occurs in 1/1000 to 1/2500 live births. On the other hand, the frequency of CFC is unknown, but it is one of the rarest RASopathies, with estimates of only a few hundred cases worldwide. However, its phenotype overlaps with that of NS. In this case series, we describe 5 patients with a clinical and genetic diagnosis of RASopathy—either NS or CFC—all of whom were also diagnosed with isolated sagittal synostosis (ISS). Medical records from ophthalmology, cardiology, plastic surgery, medical genetics, cleft craniofacial, and neurosurgery were used to determine patient history. In our cohort, late presentation of ISS was the predominant form of ISS presentation. We hope this report further characterizes the burgeoning relationship between RASopathy and ISS. Furthermore, these findings support including sagittal synostosis among the presenting features in the clinical phenotype of RASopathies. Ethical approval was obtained from the university’s institutional review board.

Childhood brain tumors: current management, biological insights, and future directions

Brain tumors are the most common solid tumors in children, and, unfortunately, many subtypes continue to have a suboptimal long-term outcome. During the last several years, however, remarkable advances in our understanding of the molecular underpinnings of these tumors have occurred as a result of high-resolution genomic, epigenetic, and transcriptomic profiling, which have provided insights for improved tumor categorization and molecularly directed therapies. While tumors such as medulloblastomas have been historically grouped into standard- and high-risk categories, it is now recognized that these tumors encompass four or more molecular subsets with distinct clinical and molecular characteristics. Likewise, high-grade glioma, which for decades was considered a single high-risk entity, is now known to comprise multiple subsets of tumors that differ in terms of patient age, tumor location, and prognosis. The situation is even more complex for ependymoma, for which at least nine subsets of tumors have been described. Conversely, the majority of pilocytic astrocytomas appear to result from genetic changes that alter a single, therapeutically targetable molecular pathway. Accordingly, the present era is one in which treatment is evolving from the historical standard of radiation and conventional chemotherapy to a more nuanced approach in which these modalities are applied in a risk-adapted framework and molecularly targeted therapies are implemented to augment or, in some cases, replace conventional therapy. Herein, the authors review advances in the categorization and treatment of several of the more common pediatric brain tumors and discuss current and future directions in tumor management that hold significant promise for patients with these challenging tumors.

Conformal Radiation Therapy for Pediatric Ependymoma, Chemotherapy for Incompletely Resected Ependymoma, and Observation for Completely Resected, Supratentorial Ependymoma

PURPOSE

The Children's Oncology Group trial ACNS0121 estimated event-free survival (EFS) and overall survival for children with intracranial ependymoma treated with surgery, radiation therapy, and-selectively-with chemotherapy. Treatment was administered according to tumor location, histologic grade, and extent of resection. The impacts of histologic grade, focal copy number gain on chromosome 1q, and DNA methylation profiles were studied for those undergoing surgery and immediate postoperative conformal radiation therapy (CRT).

METHODS

ACNS0121 included 356 newly diagnosed patients (ages 1 to 21 years). Patients with classic supratentorial ependymoma were observed after gross total resection (GTR). Those undergoing subtotal resection received chemotherapy, second surgery, and CRT. The remaining patients received immediate postoperative CRT after near-total resection or GTR. CRT was administered with a 1.0-cm clinical target volume margin. The cumulative total dose was 59.4 Gy, except for patients who underwent GTR and were younger than age 18 months (who received 54 Gy). Patients were enrolled between October 2003 and September 2007 and were observed for 5 years. Supratentorial tumors were evaluated for RELA fusion; infratentorial tumors, for chromosome 1q gain. Classification of posterior fossa groups A and B was made by methylation profiles.

RESULTS

The 5-year EFS rates were 61.4% (95% CI, 34.5% to 89.6%), 37.2% (95% CI, 24.8% to 49.6%), and 68.5% (95% CI, 62.8% to 74.2%) for observation, subtotal resection, and near-total resection/GTR groups given immediate postoperative CRT, respectively. The 5-year EFS rates differed significantly by tumor grade (P = .0044) but not by age, location, RELA fusion status, or posterior fossa A/posterior fossa B grouping. EFS was higher for patients with infratentorial tumors without 1q gain than with 1q gain (82.8% [95% CI, 74.4% to 91.2%] v 47.4% [95% CI, 26.0% to 68.8%]; P = .0013).

CONCLUSION

The EFS for patients with ependymoma younger than 3 years of age who received immediate postoperative CRT and for older patients is similar. Irradiation should remain the mainstay of care for most subtypes.

Quantifying radiation therapy response using apparent diffusion coefficient (ADC) parametric mapping of pediatric diffuse intrinsic pontine glioma: a report from the pediatric brain tumor consortium

BACKGROUND AND PURPOSE

Baseline diffusion or apparent diffusion coefficient (ADC) characteristics have been shown to predict outcome related to DIPG, but the predictive value of post-radiation ADC is less well understood. ADC parametric mapping (FDM) was used to measure radiation-related changes in ADC and compared these metrics to baseline ADC in predicting progression-free survival and overall survival using a large multi-center cohort of DIPG patients (Pediatric Brain Tumor Consortium-PBTC).

MATERIALS AND METHODS

MR studies at baseline and post-RT in 95 DIPG patients were obtained and serial quantitative ADC parametric maps were generated from diffusion-weighted imaging based on T2/FLAIR and enhancement regions of interest (ROIs). Metrics assessed included total voxels with: increase in ADC (iADC); decrease in ADC (dADC), no change in ADC (nADC), fraction of voxels with increased ADC (fiADC), fraction of voxels with decreased ADC (fdADC), and the ratio of fiADC and fdADC (fDM Ratio).

RESULTS

A total of 72 patients were included in the final analysis. Tumors with higher fiADC between baseline and the first RT time point showed a trend toward shorter PFS with a hazard ratio of 6.44 (CI 0.79, 52.79, p = 0.083). In contrast, tumors with higher log mean ADC at baseline had longer PFS, with a hazard ratio of 0.27 (CI 0.09, 0.82, p = 0.022). There was no significant association between fDM derived metrics and overall survival.

CONCLUSIONS

Baseline ADC values are a stronger predictor of outcome compared to radiation related ADC changes in pediatric DIPG. We show the feasibility of employing parametric mapping techniques in multi-center studies to quantitate spatially heterogeneous treatment response in pediatric tumors, including DIPG.

Response assessment in medulloblastoma and leptomeningeal seeding tumors: recommendations from the Response Assessment in Pediatric Neuro-Oncology committee

Lack of standard response criteria in clinical trials for medulloblastoma and other seeding tumors complicates assessment of therapeutic efficacy and comparisons across studies. An international working group was established to develop consensus recommendations for response assessment. The aim is that these recommendations be prospectively evaluated in clinical trials, with the goal of achieving more reliable risk stratification and uniformity across clinical trials. Current practices and literature review were performed to identify major confounding issues and justify subsequently developed recommendations; in areas lacking scientific investigations, recommendations were based on experience of committee members and consensus was reached after discussion. Recommendations apply to both adult and pediatric patients with medulloblastoma and other seeding tumors. Response should be assessed using MR imaging (brain and spine), CSF cytology, and neurologic examination. Clinical imaging standards with minimum mandatory sequence acquisition that optimizes detection of leptomeningeal metastases are defined. We recommend central review prior to inclusion in treatment cohorts to ensure appropriate risk stratification and cohort inclusion. Consensus recommendations and response definitions for patients with medulloblastomas and other seeding tumors have been established; as with other Response Assessment in Neuro-Oncology recommendations, these need to now be prospectively validated in clinical trials.