Towards Consistency in Pediatric Brain Tumor Measurements: Challenges, Solutions, and the Role of AI-Based Segmentation

MR imaging is central to the assessment of tumor burden and changes over time in neuro-oncology. Several response assessment guidelines have been set forth by the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working groups in different tumor histologies; however, the visual delineation of tumor components using MRIs is not always straightforward, and complexities not currently addressed by these criteria can introduce inter- and intra-observer variability in manual assessments. Differentiation of non-enhancing tumor from peritumoral edema, mild enhancement from absence of enhancement, and various cystic components can be challenging; particularly given a lack of sufficient and uniform imaging protocols in clinical practice. Automated tumor segmentation with artificial intelligence (AI) may be able to provide more objective delineations, but rely on accurate and consistent training data created manually (ground truth). Herein, this paper reviews existing challenges and potential solutions to identifying and defining subregions of pediatric brain tumors (PBTs) that are not explicitly addressed by current guidelines. The goal is to assert the importance of defining and adopting criteria for addressing these challenges, as it will be critical to achieving standardized tumor measurements and reproducible response assessment in PBTs, ultimately leading to more precise outcome metrics and accurate comparisons among clinical studies.

Indoximod-based chemo-immunotherapy for pediatric brain tumors: A first-in-children phase I trial

BACKGROUND

Recurrent brain tumors are the leading cause of cancer death in children. Indoleamine 2,3-dioxygenase (IDO) is a targetable metabolic checkpoint that, in preclinical models, inhibits anti-tumor immunity following chemotherapy.

METHODS

We conducted a phase I trial (NCT02502708) of the oral IDO-pathway inhibitor indoximod in children with recurrent brain tumors or newly diagnosed diffuse intrinsic pontine glioma (DIPG). Separate dose-finding arms were performed for indoximod in combination with oral temozolomide (200 mg/m2/day x 5 days in 28-day cycles), or with palliative conformal radiation. Blood samples were collected at baseline and monthly for single-cell RNA-sequencing with paired single-cell T cell receptor sequencing.

RESULTS

Eighty-one patients were treated with indoximod-based combination therapy. Median follow-up was 52 months (range 39-77 months). Maximum tolerated dose was not reached, and the pediatric dose of indoximod was determined as 19.2 mg/kg/dose, twice daily. Median overall survival was 13.3 months (n = 68, range 0.2-62.7) for all patients with recurrent disease and 14.4 months (n = 13, range 4.7-29.7) for DIPG. The subset of n = 26 patients who showed evidence of objective response (even a partial or mixed response) had over 3-fold longer median OS (25.2 months, range 5.4-61.9, p = 0.006) compared to n = 37 nonresponders (7.3 months, range 0.2-62.7). Four patients remain free of active disease longer than 36 months. Single-cell sequencing confirmed emergence of new circulating CD8 T cell clonotypes with late effector phenotype.

CONCLUSIONS

Indoximod was well tolerated and could be safely combined with chemotherapy and radiation. Encouraging preliminary evidence of efficacy supports advancing to Phase II/III trials for pediatric brain tumors.

Primary Diffuse Leptomeningeal Melanomatosis in a Child with Extracranial Metastasis: Case Report

Primary meningeal melanomatosis is an extremely rare tumor with very few documented responses to treatment. A 3-year-old male with a complex past medical history, including prematurity and shunted hydrocephalus, was diagnosed with primary meningeal melanomatosis with peritoneal implants. Molecular testing revealed an NRAS Q61R mutation. The patient received proton craniospinal radiation followed by immunotherapy with nivolumab (1 mg/kg) and ipilimumab (3 mg/kg) IV every 3 weeks and, upon progression, he was switched to a higher dose of nivolumab (3 mg/kg IV every 2 weeks) and binimetinib (24 mg/m2/dose, twice a day). The patient had significant improvement of CNS disease with radiation therapy and initial immunotherapy but progression of extracranial metastatic peritoneal and abdominal disease. Radiation was not administered to the whole abdomen. After two cycles of nivolumab and treatment with the MEK inhibitor binimetinib, he had radiographic and clinical improvement in abdominal metastasis and ascitis. He ultimately died from RSV infection, Klebsiella sepsis, and subdural hemorrhage without evidence of tumor progression. This is the first report of a child with primary meningeal melanomatosis with extracranial metastatic disease with response to a combination of radiation, immunotherapy and MEK inhibitor therapy.

The children's brain tumor network (CBTN) - Accelerating research in pediatric central nervous system tumors through collaboration and open science

Pediatric brain tumors are the leading cause of cancer-related death in children in the United States and contribute a disproportionate number of potential years of life lost compared to adult cancers. Moreover, survivors frequently suffer long-term side effects, including secondary cancers. The Children's Brain Tumor Network (CBTN) is a multi-institutional international clinical research consortium created to advance therapeutic development through the collection and rapid distribution of biospecimens and data via open-science research platforms for real-time access and use by the global research community. The CBTN's 32 member institutions utilize a shared regulatory governance architecture at the Children's Hospital of Philadelphia to accelerate and maximize the use of biospecimens and data. As of August 2022, CBTN has enrolled over 4700 subjects, over 1500 parents, and collected over 65,000 biospecimen aliquots for research. Additionally, over 80 preclinical models have been developed from collected tumors. Multi-omic data for over 1000 tumors and germline material are currently available with data generation for > 5000 samples underway. To our knowledge, CBTN provides the largest open-access pediatric brain tumor multi-omic dataset annotated with longitudinal clinical and outcome data, imaging, associated biospecimens, child-parent genomic pedigrees, and in vivo and in vitro preclinical models. Empowered by NIH-supported platforms such as the Kids First Data Resource and the Childhood Cancer Data Initiative, the CBTN continues to expand the resources needed for scientists to accelerate translational impact for improved outcomes and quality of life for children with brain and spinal cord tumors.

Clinical Activity of Mitogen-Activated Protein Kinase-Targeted Therapies in Patients With Non-V600 BRAF-Mutant Tumors

PURPOSE

Non-V600 mutations comprise approximately 35% of all BRAF mutations in cancer. Many of these mutations have been identified as oncogenic drivers and can be classified into three classes according to molecular characteristics. Consensus treatment strategies for class 2 and 3 BRAF mutations have not yet been established.

METHODS

We performed a systematic review and meta-analysis with published reports of individual patients with cancer harboring class 2 or 3 BRAF mutations from 2010 to 2021, to assess treatment outcomes with US Food and Drug Administration-approved mitogen-activated protein kinase (MAPK) pathway targeted therapy (MAPK TT) according to BRAF class, cancer type, and MAPK TT type. Coprimary outcomes were response rate and progression-free survival.

RESULTS

A total of 18,167 studies were screened, identifying 80 studies with 238 patients who met inclusion criteria. This included 167 patients with class 2 and 71 patients with class 3 BRAF mutations. Overall, 77 patients achieved a treatment response. In both univariate and multivariable analyses, response rate and progression-free survival were higher among patients with class 2 compared with class 3 mutations, findings that remain when analyses are restricted to patients with melanoma or lung primary cancers. MEK ± BRAF inhibitors demonstrated greater clinical activity in class 2 compared with class 3 BRAF-mutant tumors than BRAF or EGFR inhibitors.

CONCLUSION

This meta-analysis suggests that MAPK TTs have clinical activity in some class 2 and 3 BRAF-mutant cancers. BRAF class may dictate responsiveness to current and emerging treatment strategies, particularly in melanoma and lung cancers. Together, this analysis provides clinical validation of predictions made on the basis of a mutation classification system established in the preclinical literature. Further evaluation with prospective clinical trials is needed for this population.

Comprehensive Genomic Profiling of High-Risk Pediatric Cancer Patients Has a Measurable Impact on Clinical Care

PURPOSE

Profiling of pediatric cancers through deep sequencing of large gene panels and whole exomes is rapidly being adopted in many clinical settings. However, the most impactful approach to genomic profiling of pediatric cancers remains to be defined.

METHODS

We conducted a prospective precision medicine trial, using whole-exome sequencing of tumor and germline tissue and whole-transcriptome sequencing (RNA Seq) of tumor tissue to characterize the mutational landscape of 127 tumors from 126 unique patients across the spectrum of pediatric brain tumors, hematologic malignancies, and extracranial solid tumors.

RESULTS

We identified somatic tumor alterations in 121/127 (95.3%) tumor samples and identified cancer predisposition syndromes on the basis of known pathogenic or likely pathogenic germline mutations in cancer predisposition genes in 9/126 patients (7.1%). Additionally, we developed a novel scoring system for measuring the impact of tumor and germline sequencing, encompassing therapeutically relevant genomic alterations, cancer-related germline findings, recommendations for treatment, and refinement of risk stratification or prognosis. At least one impactful finding from the genomic results was identified in 108/127 (85%) samples sequenced. A recommendation to consider a targeted agent was provided for 82/126 (65.1%) patients. Twenty patients ultimately received therapy with a molecularly targeted agent, representing 24% of those who received a targeted agent recommendation and 16% of the total cohort.

CONCLUSION

Paired tumor/normal whole-exome sequencing and tumor RNA Seq of de novo or relapsed/refractory tumors was feasible and clinically impactful in high-risk pediatric cancer patients.

RARE-35. PINEOBLASTOMA IN CHILDREN SIX YEARS OF AGE OR LESS: FINAL REPORT OF THE HEAD START I, II AND III EXPERIENCE

BACKGROUND

We report the outcomes of patients with pineoblastoma enrolled on the Head Start I-III trials.

METHODS

Twenty-three children were enrolled between 1991–2009. Treatment included maximal surgical resection followed by five cycles of intensive-chemotherapy and consolidation with marrow-ablative chemotherapy and autologous hematopoietic cell rescue (HDCx/AuHCR). Irradiation following consolidation was reserved for children over six years of age or those with residual tumor at the end of induction.

RESULTS

The median age was 3.12 years (range:0.44–5.72). Three patients withdrew from the protocols and two patients experienced chemotherapy-related mortality. Eight patients experienced progressive disease (PD) during induction chemotherapy. Ten patients received HDCx/AuHCR; eight experienced PD post-consolidation. Seven patients received craniospinal irradiation (CSI) with a median dose of 20.7 Gy (range:18–36 Gy) with boost(s) (median dose 27 Gy, range:18–36 Gy); three received CSI as adjuvant therapy (2 post-HDCx/AuHCR) and four upon progression/recurrence. The 5-year progression-free survival (PFS) and overall survival (OS) were 9.7% (95%,CI:2.6–36.0%) and 13% (95%,CI:4.5–37.5%), respectively. Three patients survived beyond five years. Nineteen patients relapsed in the following sites: local site (n=4), distal site (n=6), local and distal sites (n=9). Favorable OS prognostic factors were CSI (hazard ratio (HR)=0.30 (0.11–0.86), p=0.025), and HDCx/AuHCR (HR=0.40 (0.16–0.99), p=0.047).

CONCLUSION

CSI and HDCx/AuHCR were statistically associated with improved survival. The overall poor outcomes and high PD rate during later induction cycles and following consolidation chemotherapy warrants consideration of fewer induction cycles before consolidation and the intensification of consolidation with multiple cycles of marrow-ablative chemotherapy.

Pineoblastoma in children less than six years of age: The Head Start I, II, and III experience

BACKGROUND

We report the outcomes of patients with pineoblastoma and trilateral retinoblastoma syndrome enrolled on the Head Start (HS) I-III trials.

METHODS

Twenty-three children were enrolled prospectively between 1991 and 2009. Treatment included maximal surgical resection followed by five cycles of intensive chemotherapy and consolidation with marrow-ablative chemotherapy and autologous hematopoietic cell rescue (HDCx/AuHCR). Irradiation following consolidation was reserved for children over six years of age or those with residual tumor at the end of induction.

RESULTS

Median age was 3.12 years (range, 0.44-5.72). Three patients withdrew from the study treatment and two patients experienced chemotherapy-related death. Eight patients experienced progressive disease (PD) during induction chemotherapy and did not proceed to HDCx/AuHCR. Ten patients received HDCx/AuHCR; eight experienced PD post-consolidation. Seven patients received craniospinal irradiation (CSI) with a median dose of 20.7 Gy (range, 18-36 Gy) with boost(s) (median dose 27 Gy; range, 18-36 Gy); three received CSI as adjuvant therapy (two post-HDCx/AuHCR) and four upon progression/recurrence. The five-year progression-free survival (PFS) and overall survival (OS) were 9.7% (95% confidence intervals [CI]: 2.6%-36.0%) and 13% (95% CI: 4.5%-37.5%), respectively. Only three patients survived beyond five years. Favorable OS prognostic factors were CSI (hazard ratio [HR] = 0.30 [0.11-0.86], P = 0.025) and HDCx/AuHCR (HR = 0.40 [0.16-0.99], P = 0.047).

CONCLUSIONS

Within the HS I-III trials, CSI and HDCx/AuHCR were statistically associated with improved survival. The high PD rate during later induction cycles and following consolidation chemotherapy warrants consideration of fewer induction cycles prior to consolidation and the potential intensification of consolidation with multiple cycles of marrow-ablative chemotherapy and irradiation.

The role of tumor markers for relapse detection in central nervous system non-germinomatous germ cell tumors (CNS-NGGCT): A pool analysis of cooperative group clinical trials

2503

Background: CNS-NGGCT are rare tumors that have been successfully treated with multimodal therapies. With a 5-yr EFS and OS of 72-84% and 82-93% respectively, surveillance and relapse detection is essential. Tumor marker (TM) elevation has proven to be a highly sensitive method of relapse detection in extra-cranial-NGGCT. We aim to determine the role of TM for relapse surveillance in children and adolescents with CNS-NGGCTs. Methods: European and North American data from germ cell tumor trials (SIOP GCT96, SFOP-TGM TC 90/92, COG-ACNS0122 and COG-ACNS1123) were pooled for analysis. Additionally, patients treated in the UK, Germany and France under strict protocol-guidelines were included. Details regarding imaging, pathology and TM elevation at diagnosis and relapse were collected. We report the proportion of relapses detectable by TM elevation. Results: Four-hundred and eighty-four patients enrolled in prospective cooperative group CNS-NGGCT trials from 1989 to 2016 were pooled for analysis. One-hundred and thirteen (23%) patients experienced a relapse/progression (SIOP GCT96: n = 57; SFOP TGM TC 90-92 n = 23, COG-ACNS0122 n = 16 & COG-ACNS1123 n = 17) and constitute the population of this report. Median age at diagnosis was 13 (range:1-30) years. The most common primary location was pineal in n = 60 (53%) patients. The site of relapse was available for 100 patients, 48 patients relapsed locally, 36 relapsed with distant disease, combined relapses were seen in 22 patients and 4 patients relapsed with TM elevation alone. TM in serum and/or CSF at diagnosis was available in 93(82%) patients, and in 90(80%) patients at the time of relapse. Eighty-four patients had TM available at both timepoints. At diagnosis 81 (96%) patients had TM elevation and 3 (4%) had negative TM. At relapse, 74(94%) patients with positive TM at diagnosis had TM elevation, while 7(6%) had TM negative. Conversely, 2/3 patients with negative TM at diagnosis, relapsed with elevated TM. Conclusions: Herein, we have assembled the largest prospective cohort to date of relapsed intracranial germ cell tumors. TM are highly sensitive detecting relapse/progression in CNS-NGGCT patients with elevated TM at diagnosis. The routine use of TM for relapse surveillance in patients with CNS-NGGCT can decrease the frequency of cross-sectional imaging, therefore, reducing lengthy hospital visits, sedation procedures and decreasing health-care costs.

Advanced ADC Histogram, Perfusion, and Permeability Metrics Show an Association with Survival and Pseudoprogression in Newly Diagnosed Diffuse Intrinsic Pontine Glioma: A Report from the Pediatric Brain Tumor Consortium

BACKGROUND AND PURPOSE

Diffuse intrinsic pontine glioma is a lethal childhood brain cancer with dismal prognosis and MR imaging is the primary methodology used for diagnosis and monitoring. Our aim was to determine whether advanced diffusion, perfusion, and permeability MR imaging metrics predict survival and pseudoprogression in children with newly diagnosed diffuse intrinsic pontine glioma.

MATERIALS AND METHODS

A clinical trial using the poly (adenosine diphosphate ribose) polymerase (PARP) inhibitor veliparib concurrently with radiation therapy, followed by maintenance therapy with veliparib + temozolomide, in children with diffuse intrinsic pontine glioma was conducted by the Pediatric Brain Tumor Consortium. Standard MR imaging, DWI, dynamic contrast-enhanced perfusion, and DSC perfusion were performed at baseline and approximately every 2 months throughout treatment. ADC histogram metrics of T2-weighted FLAIR and enhancing tumor volume, dynamic contrast-enhanced permeability metrics for enhancing tumors, and tumor relative CBV from DSC perfusion MR imaging were calculated. Baseline values, post-radiation therapy changes, and longitudinal trends for all metrics were evaluated for associations with survival and pseudoprogression.

RESULTS

Fifty children were evaluable for survival analyses. Higher baseline relative CBV was associated with shorter progression-free survival (P = .02, Q = 0.089) and overall survival (P = .006, Q = 0.055). Associations of higher baseline mean transfer constant from the blood plasma into the extravascular extracellular space with shorter progression-free survival (P = .03, Q = 0.105) and overall survival (P = .03, Q = 0.102) trended toward significance. An increase in relative CBV with time was associated with shorter progression-free survival (P < .001, Q < 0.001) and overall survival (P = .004, Q = 0.043). Associations of longitudinal mean extravascular extracellular volume fraction with progression-free survival (P = .03, Q = 0.104) and overall survival (P = .03, Q = 0.105) and maximum transfer constant from the blood plasma into the extravascular extracellular space with progression-free survival (P = .03, Q = 0.102) trended toward significance. Greater increases with time were associated with worse outcomes. True radiologic progression showed greater post-radiation therapy decreases in mode_ADC_FLAIR compared with pseudoprogression (means, -268.15 versus -26.11, P = .01.) CONCLUSIONS: ADC histogram, perfusion, and permeability MR imaging metrics in diffuse intrinsic pontine glioma are useful in predicting survival and pseudoprogression.

A phase II clinical study of pomalidomide (CC-4047) monotherapy for children and young adults with recurrent or progressive primary brain tumors

10035

Background: Central nervous system (CNS) tumors are the most common cause of pediatric cancer mortality and novel therapies are needed for refractory disease. Pomalidomide (pom) is an oral immunomodulatory agent with CNS penetration, anti-angiogenic, anti-inflammatory and cytotoxic activity. Methods: This Phase 2 study evaluated both safety and efficacy of pom in pediatric patients with recurrent/progressive CNS tumors. Using a Simon’s two-stage design, patients were stratified to high-grade glioma [HGG], ependymoma, medulloblastoma or diffuse intrinsic pontine glioma [DIPG] cohorts. Patients received pom 2.6 mg/m2 for 21 days of a 28-day cycle. The primary endpoint was objective response rate (complete response [CR], partial response [PR]) or prolonged stable disease [SD] (defined as ≥ 6 cycles, or ≥ 3 for DIPG). Stage 1 required ≥ 2/9 subjects, within each cohort, to have a response or prolonged SD to move into Stage 2, and ≥ 5/20 responders or patients with prolonged SD at the end of Stage 2 for pom to be deemed effective. Results: Of 52 treated patients (median age 11.5 y/o; range 4-18), 47 were evaluable for primary endpoint. Median treatment duration was 2 cycles (range 1-16). Only the HGG cohort met protocol-defined criteria to advance to Stage 2, with one PR and one prolonged SD in Stage 1. Forty-six of 47 evaluable patients discontinued pom, due to adverse event (n = 1; pneumonia), withdrawal by parent/guardian (n = 2), death (n = 4; 3 progressive disease, 1 sepsis), or progressive disease (n = 39). Nineteen of 52 treated patients experienced ≥ 1 grade 3–4 treatment-emergent adverse event (TEAE) related to pom, neutropenia (n = 15) being the most commonly reported. Twenty-six patients died on study. All deaths were attributed to either disease progression or complications from disease. Conclusions: Single agent pomalidomide failed to meet a clinically meaningful level of efficacy in children with recurrent/progressive HGG, DIPG, medulloblastoma or ependymoma. However, it should be noted that a sustained response was observed in a child with HGG, replicating the outcome observed in one child with HGG in the Phase 1 (PBTC-043) trial. Clinical trial information: NCT03257631.

A phase I trial of pomalidomide for children with recurrent, progressive/refractory central nervous system (CNS) tumors: A Pediatric Brain Tumor Consortium (PBTC) study

10543

Background: CNS malignancies are the most common solid tumors among children. Novel therapies are needed to help improve the survival outcomes in children with recurrent disease. Pomalidomide is an immunomodulatory agent thought to also function through a combination of anti-angiogenic, anti-inflammatory and cytotoixic activity making it a good candidate to explore in pediatric CNS tumors. Methods: A Phase I trial of pomalidomide was conducted among children ≥ 3 to < 21 years old with recurrent, progressive/refractory CNS tumors using the “rolling 6” dose escalation design. The primary objective was to determine the maximum tolerated dose (MTD) and/or recommended Phase II dose (RP2D) when given orally once daily for 21 consecutive days of a 28-day course. Once the MTD was established, 12 additional patients were enrolled on expansion cohorts based on age and steroid use. Results: 29 children were enrolled and 25 were evaluable for dose limiting toxicity (DLT) evaluation. The MTD was 2.6 mg/m2 (Dose level 2). DLTs observed at dose level 3 (3.4 mg/m2) included diarrhea (n = 1), thrombocytopenia (n = 1) and lung infection (n = 1), all grade 3. The most common toxicities were grade 1 lymphopenia (55%), leukopenia (62%) and thrombocytopenia (38%). There were no obvious differences in tolerability based on age or steroid use. Pharmacokinetics were similar to those observed in adults and increased in a dose-dependent manner. At the RP2D of 2.6 mg/m2, the Cmax was 97.4 ng/mL and the t½ was 4.1 hours. The median number of treatment cycles was 1.6 (0.2-12.3). Two patients, one with an oligodendroglioma and one with anaplastic pleomorphic xanthoastrocytoma, had long term stable disease for 9 and 18+ cycles. No objective responses were observed. Twelve month progression-free and overall-survivals were 5.2+/-3.6% and 12.8+/-8.5%, respectively. Immunologic correlate analyses are ongoing. Conclusions: The RP2D of pomalidomide is 2.6 mg/m2 in children with recurrent brain tumors. Further prospective evaluation of this agent alone or in combination will be necessary to better understand its efficacy in specific pediatric CNS tumor populations. Clinical trial information: NCT02415153.

A phase II prospective study of selumetinib in children with recurrent or refractory low-grade glioma (LGG): A Pediatric Brain Tumor Consortium (PBTC) study

10504

Background: A greater understanding of the Ras-MAP kinase-signaling pathway in pediatric low-grade glioma (LGG) paired with the availability of potent selective inhibitors has enhanced the ability to target this pathway with therapeutic intent. Methods: The PBTC conducted a multi-institutional phase II study (NCT01089101) evaluating selumetinib (AZD6244, ARRY-142886), a MEK I/II inhibitor, in children with recurrent/refractory LGG assigned to 6 strata and treated at 25 mg/m2/dose PO BID for up to two years. Here we present the data from three of these strata. The remaining strata are still accruing patients. Results: Stratum I included children with non-NF-1 and non-optic pathway recurrent/refractory pilocytic astrocytoma (PA) harboring BRAF aberrations (BRAF V600e mutation or the BRAF-KIAA 1549 fusion). Eight of 25 (32%) patients achieved a partial response (PR) with 2-year PFS of 66+/-11%. Two of 7 (29%) patient tumors with a BRAF V600e mutation and 6/18 (33%) with a BRAF KIAA-1549 fusion had a PR. Stratum 3 enrolled NF-1-associated LGG. Tissue for tumor BRAF evaluation was not required for eligibility. Ten of 25 (40%) achieved PR with a 2-year PFS of 96+/-4%. Only one patient progressed while on treatment. Stratum 4 included children with non-NF-1 optic pathway/hypothalamic LGG. Tissue for tumor BRAF evaluation was not required for eligibility. Two of 16 (12.5%) had a PR with a 2-year PFS of 65+/-13%. The BRAF aberration status of the responders in strata 3 and 4 is mostly unknown. All responses were confirmed centrally and seven patients remain on treatment. The most common toxicities were grade 1/2 CPK elevation, diarrhea, hypoalbuminemia, elevated AST and rash. Rare grade 3/4 toxicities included elevated CPK, rash, neutropenia, emesis and paronychia. Conclusions: Selumetinib was effective in treating children with recurrent/refractory LGG, including those with NF-1 associated LGG and PA harboring BRAF V600e mutation or BRAF-KIAA 1549 fusion. Larger prospective studies are necessary to determine the future, specific role of this agent in treating children with LGG harboring specific molecular aberrations. Clinical trial information: NCT01089101.

Integrated (epi)-Genomic Analyses Identify Subgroup-Specific Therapeutic Targets in CNS Rhabdoid Tumors

We recently reported that atypical teratoid rhabdoid tumors (ATRTs) comprise at least two transcriptional subtypes with different clinical outcomes; however, the mechanisms underlying therapeutic heterogeneity remained unclear. In this study, we analyzed 191 primary ATRTs and 10 ATRT cell lines to define the genomic and epigenomic landscape of ATRTs and identify subgroup-specific therapeutic targets. We found ATRTs segregated into three epigenetic subgroups with distinct genomic profiles, SMARCB1 genotypes, and chromatin landscape that correlated with differential cellular responses to a panel of signaling and epigenetic inhibitors. Significantly, we discovered that differential methylation of a PDGFRB-associated enhancer confers specific sensitivity of group 2 ATRT cells to dasatinib and nilotinib, and suggest that these are promising therapies for this highly lethal ATRT subtype.

Molecular subgroups of atypical teratoid rhabdoid tumours in children: an integrated genomic and clinicopathological analysis

BACKGROUND

Rhabdoid brain tumours, also called atypical teratoid rhabdoid tumours, are lethal childhood cancers with characteristic genetic alterations of SMARCB1/hSNF5. Lack of biological understanding of the substantial clinical heterogeneity of these tumours restricts therapeutic advances. We integrated genomic and clinicopathological analyses of a cohort of patients with atypical teratoid rhabdoid tumours to find out the molecular basis for clinical heterogeneity in these tumours.

METHODS

We obtained 259 rhabdoid tumours from 37 international institutions and assessed transcriptional profiles in 43 primary tumours and copy number profiles in 38 primary tumours to discover molecular subgroups of atypical teratoid rhabdoid tumours. We used gene and pathway enrichment analyses to discover group-specific molecular markers and did immunohistochemical analyses on 125 primary tumours to evaluate clinicopathological significance of molecular subgroup and ASCL1-NOTCH signalling.

FINDINGS

Transcriptional analyses identified two atypical teratoid rhabdoid tumour subgroups with differential enrichment of genetic pathways, and distinct clinicopathological and survival features. Expression of ASCL1, a regulator of NOTCH signalling, correlated with supratentorial location (p=0·004) and superior 5-year overall survival (35%, 95% CI 13-57, and 20%, 6-34, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·033) in 70 patients who received multimodal treatment. ASCL1 expression also correlated with superior 5-year overall survival (34%, 7-61, and 9%, 0-21, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·001) in 39 patients who received only chemotherapy without radiation. Cox hazard ratios for overall survival in patients with differential ASCL1 enrichment treated with chemotherapy with or without radiation were 2·02 (95% CI 1·04-3·85; p=0·038) and 3·98 (1·71-9·26; p=0·001). Integrated analyses of molecular subgroupings with clinical prognostic factors showed three distinct clinical risk groups of tumours with different therapeutic outcomes.

INTERPRETATION

An integration of clinical risk factors and tumour molecular groups can be used to identify patients who are likely to have improved long-term radiation-free survival and might help therapeutic stratification of patients with atypical teratoid rhabdoid tumours.

FUNDING

C17 Research Network, Genome Canada, b.r.a.i.n.child, Mitchell Duckman, Tal Doron and Suri Boon foundations.

Diffuse intrinsic pontine gliomas (DIPG) in adolescents can have differing presentations but similar outcomes compared to those of middle childhood

2101

Background: DIPG are invasive, treatment-resistant, brainstem tumors that generally affect children in middle childhood. The triad of cranial neuropathies, long tract signs, and ataxia are characteristic presenting signs; most patients have a short history of symptoms. Median survival is less than one year, but young children (<3 years) and adults with DIPG may have a better prognosis. Other positive clinical prognostic factors include longer duration of symptoms and absence of cranial neuropathies. We assessed the presentation and outcome of adolescents with DIPG. Methods: Patients were enrolled on an IRB-approved protocol. Clinical data for patients age>10 years and <20 years with a diagnosis of DIPG who were evaluated and treated at the authors’ institutions were reviewed. Results: A total of 46 patients were identified. M:F was 0.77:1. Median age at diagnosis was 13 (range 10-20) yrs. Frequent presenting symptoms included headache (39 %), dizziness (25%), diplopia (27%) and cranial neuropathies (27%). Two were diagnosed as incidental findings. The interval between onset of symptoms and diagnosis ranged from 2 days-5 years, and only 9 of 41 patients (22%) reported symptom duration of less than 2 weeks. The majority (39/42) received radiation therapy, with or without adjuvant chemotherapy. Of patients for whom data is available, 8/22 (36%) did not improve or worsened during radiation therapy and 17 of 27 (63%) remained on steroids at the end of radiation. Two patients are alive with stable disease and 1 is actively receiving initial treatment. Of the patients with progressive disease for whom data is available (n=32), median time to progression was 8 mo (range 2 mo-2.5 yrs). Conclusions: Presenting symptoms of DIPG in adolescents commonly include headache, dizziness and diplopia for several weeks-months. Although the vast majority are treated with radiation therapy, clinical benefit was not observed in a significant number of patients. Overall outcome is similar to those patients diagnosed in middle childhood rather than the adult population.

Growth hormone excess in children with neurofibromatosis type 1-associated and sporadic optic pathway tumors

OBJECTIVE

To describe the clinical manifestations of growth hormone (GH) excess in children with optic pathway tumors (OPT).

STUDY DESIGN

Descriptive case series of 5 children with OPT, 3 with associated neurofibromatosis type 1, referred for evaluation of accelerated linear growth. GH excess was evaluated by oral glucose tolerance tests with frequent sampling of GH levels. Precocious puberty was evaluated by basal luteinizing hormone and sex steroid hormone levels. Stimulation testing with leuprolide acetate (20 μg/kg subcutaneously) was conducted in patients with normal baseline testing.

RESULTS

All patients had OPT involving both the hypothalamus and optic chiasm. All patients had elevated levels of the growth factor insulin-like growth factor 1 and on stimulation testing demonstrated an inability to suppress GH levels to < 1.0 ng/mL, indicating the presence of unregulated GH secretion. Additionally, all patients displayed biochemical evidence of precocious puberty.

CONCLUSIONS

GH excess may be an under-recognized occurrence in the setting of neurofibromatosis type 1 and OPT. GH excess in such patients may contribute to continued brain tumor growth. Given the potential adverse consequences of unrestrained GH excess, all children with chiasmal or hypothalamic tumors who have rapid growth should be evaluated for both precocious puberty and GH excess.

Brainstem primitive neuroectodermal tumors (bstPNET): results of treatment with intensive induction chemotherapy followed by consolidative chemotherapy with autologous hematopoietic cell rescue

We have evaluated the response rate and survival utilizing intensified chemotherapy followed by myeloablative chemotherapy with autologous hematopoietic cell rescue (AuHCR) and adjuvant radiation therapy in six young children with newly diagnosed brainstem primitive neuroectodermal tumors (bstPNET). Following maximum surgical resection of the tumor, patients received high dose induction chemotherapy including vincristine, cisplatin, cyclophosphamide, and etoposide. Eligible patients received a single cycle of myeloablative chemotherapy followed by AuHCR. Two patients survive at least 32 months with stable disease. This approach provides an alternative for young patients with bstPNET who in prior reports have had a uniformly fatal prognosis.

Dissecting the role of endothelial SURVIVIN DeltaEx3 in angiogenesis

The identification of alternative splice variants of Survivin that possess distinct functions from those originally identified for the main Survivin isoform has greatly increased the complexity of our understanding of the role of Survivin in different cells. Previous functional studies of the Survivin splice variants have been performed almost exclusively in cancer cells. However, Survivin has increasingly been implicated in other normal physiologic and pathophysiologic processes, including angiogenesis. In this study, we dissect the involvement of Survivin DeltaEx3 in angiogenesis. We show by confocal microscopy that a pool of endothelial Survivin DeltaEx3 is localized to membrane ruffles. We also demonstrate that Survivin DeltaEx3 is the Survivin splice variant responsible for modulating angiogenesis in vitro, in tube formation assays, and in vivo, in an in vivo angiogenesis assay. Our data indicate that Survivin DeltaEx3 may regulate angiogenesis via several mechanisms including cell invasion, migration, and Rac1 activation. Our findings identify a novel pathway regulating angiogenesis through Survivin DeltaEx3 and a novel mechanism for Rac1 activation during angiogenesis. In conclusion, our results provide new insights into the regulation of endothelial cell homeostasis and angiogenesis by the Survivin proteins.

Survivin: an inhibitor of apoptosis in pediatric cancer

Survivin is an inhibitor of apoptosis protein (IAP) expressed in a large number of adult malignancies. Its expression levels correlate with more aggressive disease and poor clinical outcome in many of these tumors. As its expression is restricted in normal adult differentiated tissues, it has become of great interest as both a tumor prognostic marker and as a potential biologic target for future anti-cancer therapies. Survivin expression and Survivin-based therapies have been examined in many of the more common pediatric malignancies. We present an overview of Survivin function and current research exploring its biologic and therapeutic roles in pediatric tumors.

Survivin, Survivin-2B, and Survivin-deItaEx3 expression in medulloblastoma: biologic markers of tumour morphology and clinical outcome

Survivin is an apoptotic inhibitor that is expressed at high levels in a variety of malignancies. Survivin has four known alternative splice forms (Survivin, Survivin-2B, Survivin-deltaEx3, and Survivin-3B), and the recent literature suggests that these splice variants have unique functions and subcellular localisation patterns. We evaluated 19 fresh-frozen paediatric medulloblastomas for the expression of three Survivin isoforms by quantitative PCR. Survivin was most highly expressed when compared with normal cerebellar tissue. We also investigated Survivin protein expression in 40 paraffin-embedded paediatric medulloblastoma tumours by immunohistochemistry. We found a statistically significant association between the percentage of Survivin-positive cells and histologic subtype, with the large-cell-anaplastic variant expressing Survivin at higher levels than the classic subtype. We also found a statistically significant relationship between the percent of Survivin-positive cells in the tumours and clinical outcome, with higher levels of Survivin correlating with a worse prognosis. In summary, our study demonstrates a role for Survivin as a marker of tumour morphology and clinical outcome in medulloblastoma. Survivin may be a promising future prognostic tool and potential biologic target in this malignancy.