Phase II Trial of Dabrafenib Plus Trametinib in Relapsed/Refractory BRAF V600-Mutant Pediatric High-Grade Glioma

PURPOSE

BRAF V600 mutation is detected in 5%-10% of pediatric high-grade gliomas (pHGGs), and effective treatments are limited. In previous trials, dabrafenib as monotherapy or in combination with trametinib demonstrated activity in children and adults with relapsed/refractory BRAF V600-mutant HGG.

METHODS

This phase II study evaluated dabrafenib plus trametinib in patients with relapsed/refractory BRAF V600-mutant pHGG. The primary objective was overall response rate (ORR) by independent review by Response Assessment in Neuro-Oncology criteria. Secondary objectives included ORR by investigator determination, duration of response (DOR), progression-free survival, overall survival (OS), and safety.

RESULTS

A total of 41 pediatric patients with previously treated BRAF V600-mutant HGG were enrolled. At primary analysis, median follow-up was 25.1 months, and 51% of patients remained on treatment. Sixteen of 20 discontinuations were due to progressive disease in this relapsed/refractory pHGG population. Independently assessed ORR was 56% (95% CI, 40 to 72). Median DOR was 22.2 months (95% CI, 7.6 months to not reached [NR]). Fourteen deaths were reported. Median OS was 32.8 months (95% CI, 19.2 months to NR). The most common all-cause adverse events (AEs) were pyrexia (51%), headache (34%), and dry skin (32%). Two patients (5%) had AEs (both rash) leading to discontinuation.

CONCLUSION

In relapsed/refractory BRAF V600-mutant pHGG, dabrafenib plus trametinib improved ORR versus previous trials of chemotherapy in molecularly unselected patients with pHGG and was associated with durable responses and encouraging survival. These findings suggest that dabrafenib plus trametinib is a promising targeted therapy option for children and adolescents with relapsed/refractory BRAF V600-mutant HGG.

Carbon-Ion Radiotherapy for Postoperative Locoregional Recurrence of Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

To evaluate the efficacy and safety of carbon-ion radiotherapy (CIRT) for patients with locoregional recurrence after surgery for pancreatic cancer.

MATERIALS/METHODS

A total of 32 patients, who underwent CIRT for locoregional recurrence after surgery for pancreatic cancer between January 2015 and July 2022, were retrospectively analyzed. The total dose of CIRT was 55.2 Gy (RBE) in 12 fractions. Concurrent chemotherapy included gemcitabine for 17 patients and S-1 for 3 patients. The overall survival (OS), local control (LC), progression free survival (PFS), and toxicity were evaluated.

RESULTS

The median follow-up time from the initiation of CIRT was 21.4 months. The 1- and 2-year OS were 84.2 and 55.3%, respectively. The median survival were 24.2 months. The 1- and 2-year PFS were 40.7 and 14.8%, respectively, with a median PFS of 9.9 months. The 1- and 2-year LC were 100 and 50.2 %, respectively. 4 patients experienced grade 3 acute toxicities: hematologic toxicity in 2 patients, anorexia in 1 patient and gastric ulcer/bleeding in 1 patient. The patients with grade 3 gastric ulcer/bleeding underwent blood transfusion and recovered quickly. There was no grade 4 or 5 acute toxicity. In terms of late toxicity, no grade 3 or greater toxicity was observed.

CONCLUSION

CIRT for postoperative locoregional recurrence of pancreatic cancer resulted in relatively long survival with acceptable toxicity. CIRT may be one of the choices of treatment for patients with this disease.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of immunotherapy in patients with DNA mismatch repair deficient (dMMR) tumors, third edition

BACKGROUND

Clinical trials have reported the efficacy of immune checkpoint inhibitors in the treatment of mismatch repair-deficient (dMMR) advanced solid tumors. The accumulated evidence of tumor agnostic agent has been made since PD-1 inhibitor was approved and used in clinical practice. Therefore, we have revised the guideline "Japan Society of Clinical Oncology provisional clinical opinion for the diagnosis and use of immunotherapy in patients with deficient DNA mismatch repair tumors, cooperated by Japanese Society of Medical Oncology, First Edition".

METHODS

Clinical questions regarding medical care were formulated for patients with dMMR advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by Japan Society of Clinical Oncology (JSCO), Japanese Society of Medical Oncology (JSMO), and Japanese society of pediatric hematology/oncology (JSPHO) voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO and the public comments among all societies' members were done.

RESULTS

The current guideline describes two clinical questions and eight recommendations for whom, when, and how MMR status should be tested.

CONCLUSION

In this guideline, the committee proposed eight recommendations for performing MMR testing properly to select patients who are likely to benefit from immunotherapy.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of immunotherapy in patients with high tumor mutational burden tumors

The development of novel antitumor agents and accompanying biomarkers has improved survival across several tumor types. Previously, we developed recommendations for tumor-agnostic treatments in patients with solid tumors with DNA mismatch repair deficient or neurotrophic receptor tyrosine kinase fusions. Recently, immune checkpoint inhibitors have shown efficacy in patient with tumor mutation burden-high (TMB-H) solid tumors and have been established as a third tumor-agnostic agent, making it necessary to develop the guideline prioritized for these patients. Clinical questions regarding medical care were formulated for patients with TMB-H advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by Japan Society of Clinical Oncology (JSCO), Japanese Society of Medical Oncology (JSMO), and Japanese society of pediatric hematology/oncology (JSPHO) voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO, and the public comments among all societies' members was done. The current guideline describes three clinical questions and seven recommendations for whom, when, and how TMB should be tested, and what is recommended for patients with TMB-H advanced solid tumors. In this guideline, the committee proposed seven recommendations for performing TMB testing properly to select patients who are likely to benefit from immunotherapy.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of tropomyosin receptor kinase inhibitors in adult and pediatric patients with neurotrophic receptor tyrosine kinase fusion-positive advanced solid tumors

BACKGROUND

Clinical trials have reported the efficacy of tropomyosin receptor kinase (TRK) inhibitors against neurotrophic receptor tyrosine kinase (NTRK) fusion gene-positive advanced solid tumors. The accumulated evidence of tumor-agnostic agent has made since TRK inhibitors were approved and used in clinical practice. Therefore, we have revised the 'Japan Society of Clinical Oncology (JSCO)/Japanese Society of Medical Oncology (JSMO)-led clinical recommendations on the diagnosis and use of tropomyosin receptor kinase inhibitors in adult and pediatric patients with neurotrophic receptor tyrosine kinase fusion-positive advanced solid tumors, cooperated by the Japanese Society of Pediatric Hematology/Oncology (JSPHO)'.

METHODS

Clinical questions regarding medical care were formulated for patients with NTRK fusion-positive advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by JSCO, JSMO, and JSPHO voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO, and the public comments among all societies' members was done.

RESULTS

The current guideline describes 3 clinical questions and 14 recommendations for whom, when, and how NTRK fusion should be tested, and what is recommended for patients with NTRK fusion-positive advanced solid tumors.

CONCLUSION

The committee proposed 14 recommendations for performing NTRK testing properly to select patients who are likely to benefit from TRK inhibitors.

Feasibility and Toxicity of Interval-Compressed Chemotherapy in Asian Children and Young Adults with Sarcoma

Twelve Asian patients with sarcoma received interval-compressed (ic-) chemotherapy scheduled every 14 days with a regimen of vincristine (2 mg/m²), doxorubicin (75 mg/m²), and cyclophosphamide (1200-2200 mg/m²) (VDC) alternating with a regimen of ifosfamide (9000 mg/m²) and etoposide (500 mg/m²) (IE), with filgrastim (5-10 mcg/kg/day) between cycles. Carboplatin (800 mg/m²) was added for CIC-rearranged sarcoma. The patients were treated with 129 cycles of ic-VDC/IE with a median interval of 19 days (interquartile range [IQR], 15-24 days. Median nadirs (IQR) were neutrophil count, 134 (30-396) × 10⁶/L at day 11 (10-12), recovery by day 15 (14-17) and platelet count, 35 (23-83) × 10⁹/L at day 11 (10-13), recovery by day 17 (14-21). Fever and bacteremia were observed in 36% and 8% of cycles, respectively. The diagnoses were Ewing sarcoma (6), rhabdomyosarcoma (3), myoepithelial carcinoma (1), malignant peripheral nerve sheath tumor (1), and CIC-DUX4 Sarcoma (1). Seven of the nine patients with measurable tumors responded (one CR and six PR). Interval-compressed chemotherapy is feasible in the treatment of Asian children and young adults with sarcomas.

Prevalence of pathogenic variants in cancer-predisposing genes in second cancer after childhood solid cancers

BACKGROUND

Second malignant neoplasms (SMNs) are one of the most severe late complications after pediatric cancer treatment. However, the effect of genetic variation on SMNs remains unclear. In this study, we revealed germline genetic factors that contribute to the development of SMNs after treatment of pediatric solid tumors.

METHODS

We performed whole-exome sequencing in 14 pediatric patients with SMNs, including three brain tumors.

RESULTS

Our analysis revealed that five of 14 (35.7%) patients had pathogenic germline variants in cancer-predisposing genes (CPGs), which was significantly higher than in the control cohort (p < 0.01). The identified genes with variants were TP53 (n = 2), DICER1 (n = 1), PMS2 (n = 1), and PTCH1 (n = 1). In terms of the type of subsequent cancer, leukemia and multiple episodes of SMN had an exceptionally high rate of CPG pathogenic variants. None of the patients with germline variants had a family history of SMN development. Mutational signature analysis showed that platinum drugs contributed to the development of SMN in three cases, which suggests the role of platinum agents in SMN development.

CONCLUSIONS

We highlight that overlapping effects of genetic background and primary cancer treatment contribute to the development of second cancers after treatment of pediatric solid tumors. A comprehensive analysis of germline and tumor samples may be useful to predict the risk of secondary cancers.

Temperature dependent local inhomogeneity and magnetic moments of (Li1-xFex)OHFeSe superconductors

We have combined the extended X-ray absorption fine structure (EXAFS) and X-ray emission spectroscopy (XES) to investigate the local structure and the local iron magnetic moments of (Li_1-xFe_x)OHFeSe (x∼0.2) superconductors. The local structure, studied by Fe K-edge EXAFS measurements, is found to be inhomogeneous that is characterized by different Fe-Se bond lengths. The inhomogeneous phase exhibits a peculiar temperature dependence with lattice anomalies in the local structural parameters at the critical temperature T_c (36 K) and at the spin density wave (SDW) transition temperature T_N (130 K). Fe Kβ XES shows iron to be in a low spin state with the local Fe magnetic moment evolving anomalously as a function of temperature. Apart from a quantitative measurement of the local structure of (Li_1-xFe_x)OHFeSe, providing direct evidence of nanoscale inhomogeneity, the results provide further evidence of the vital role that the coupled electronic, lattice and magnetic degrees of freedom play in the iron-based superconductors.

Selumetinib in Japanese pediatric patients with neurofibromatosis type 1 and symptomatic, inoperable plexiform neurofibromas: An open-label, phase I study

Background

Plexiform neurofibromas (PN) are a manifestation of neurofibromatosis type 1 (NF1) that may cause morbidity and impact health-related quality of life (HRQoL). Selumetinib (ARRY-142886, AZD6244) is an orally available, selective, mitogen-activated protein kinase kinase 1/2 inhibitor approved for children with NF1 and symptomatic, inoperable PN in regions including the USA (aged ≥2 years), EU (≥3 years), and Japan (≥3 years). This open-label, single-arm, phase I study evaluated selumetinib in Japanese children with NF1 and symptomatic, inoperable PN.

Methods

Eligible patients (aged 3-18 years) received oral selumetinib (25 mg/m² twice daily) continuously in 28-day cycles in a fasted state. Primary objectives were safety and tolerability. Secondary objectives included pharmacokinetics, efficacy, PN-related morbidities, and HRQoL.

Results

Twelve patients (median age 13.3 years) were enrolled, received ≥1 selumetinib dose (data cutoff: cycle 13 day 1) with median follow-up of 11.5 months. All patients had baseline PN-related morbidities, most commonly disfigurement (91.7%) and pain (58.3%). Most frequently reported any-grade adverse events were dermatologic and gastrointestinal. Objective response rate was 33.3%; median duration of response was not reached. Most patients (83.3%) had target PN volume reduction versus baseline. No patients reported worsening of PN-related morbidities. Selumetinib was rapidly absorbed with moderate-to-high inter-patient variability in maximum plasma concentration and area under the concentration-time curve from time 0-6 hours.

Conclusions

Consistent with results of the phase II SPRINT trial, 25 mg/m² selumetinib twice daily was well tolerated with a manageable safety profile in Japanese children with NF1 and symptomatic, inoperable PN.

BOT-3 GENOME-WIDE ASSOCIATION STUDY OF INTRACRANIAL GERM CELL TUMORS: A COMMON DELETION ATBAK1 ATTENUATES THE ENHANCER ACTIVITY AND CONFERS RISK FOR THE BRAIN TUMORS IN CHILDREN ADOLESCENTS AND YOUNG ADULTS

Intracranial germ cell tumors (IGCTs) are rare brain tumors that mainly occur in children, adolescents and young adults with a particularly high incidence in East Asian populations. The biological basis of these tumors is still largely unknown. We conduct a genome-wide association study (GWAS) of 133 patients with IGCTs and 762 controls of Japanese ancestry by using Infinium Asian Screening Array and other molecular biology methods. A common 4-bp deletion polymorphism in an enhancer adjacent to BAK1 is significantly associated with the disease risk (rs3831846; P = 2.4 × 10−9, odds ratio = 2.46 [95% CI: 1.83-3.31], minor allele frequency = 0.43). Rs3831846 is in strong linkage disequilibrium with a testicular GCTs susceptibility variant rs210138. Expression quantitative trait locus (eQTL) analysis using the GTEx dataset reveals that the risk allele of rs3831846 has a down-regulating effect on BAK1 expression in a wide range of tissues. Further in-vitro reporter assays reveal rs3831846 to be a functional variant attenuating the enhancer activity. BAK1 is a pro-apoptotic member of the BCL-2 family, thus our results suggested that the risk allele may contribute to IGCTs predisposition through down-regulating BAK1 expression. Risk alleles of testicular GCTs derived from the European GWAS show significant positive correlations in the effect sizes with the Japanese IGCTs GWAS (P = 1.3 × 10-4, Spearman’s ρ = 0.48). Of the 57 loci, 11 exhibit significant association with IGCTs and these loci were implicated in a broad range of biological pathways, including KIT/KITLG signaling, apoptosis regulation, and telomerase activity. The risk allele frequency of rs3831846 is higher in east Asia than Europe (0.49 vs. 0.20), which may provide a partial explanation for the ethnic difference in incidence. Nevertheless, our results suggest the shared genetic susceptibility of GCTs beyond ethnicity and primary sites.

PEDT-19 RECENT PROGRESS IN CHILDHOOD BRAIN TUMORS RESEARCH

The multidisciplinary standard of care for medulloblastoma, a typical pediatric malignant brain tumor of cerebellar primary origin, has been established by large RCTs in the United States. The results of the Phase III RCTs sponsored by Children's Oncology Group's for newly-diagnosed medulloblastoma in children 3 years of age and older, ACNS0331, which attempted radiotherapy reduction for the average-risk group, and ACNS0332, which attempted intensified treatment with carboplatin as a radiosensitizer and isotretinoin as an apoptosis inducer for high-risk group are discussed.It has recently been reported that some infantile glioma cells have activating fusion genes with tyrosine kinase receptor genes, including NTRK, and that TRK inhibitors are effective against these tumors, and two TRK inhibitors have been used with cancer genome panel tests as companion diagnostics, Two TRK inhibitors can now be available for glioma treatment in Japanese practice. The results of clinical trials on the efficacy of these targeting agents in brain tumors with NTRK mutations will be presented.CAR-T cell therapy was developed for GD2 following HER2, which had attracted attention as an immunotherapeutic target for pediatric glioma, and its efficacy was demonstrated in clinical trials. We will examine the results of clinical trials of this immunotherapy, a promising treatment for DMS/DIPG, the disease with absolutely poor prognosis with no effective drug therapy, although it is used in a small number of cases.

PEDT-18 PHASE I/II TRIAL OF OP-10 (ONC201) IN JAPANESE PATIENTS WITH RELAPSED OR REFRACTORY DIFFUSE MIDLINE GLIOMA

Background

Diffuse midline glioma (DMG) occurs mainly in the brain stem and most of patients have the mutation of histone (H3K27M). The prognosis is poor, and median overall survival (OS) is less than 12 months. OP-10 (ONC201) have antagonistic activity against dopamine D2 ha and to activate ClpP, a mitochondrial protease, leading tumor cells to apoptosis. We conducted a multicenter, single-arm, open-label phase I/II study of OP-10 in Japan.

Methods

A 3 + 3 design was used to determine the recommended dose of OP-10 for nine patients with recurrent or refractory glioma in the phase-I trial. Patients with recurrent or refractory DMG in the phase-II trial orally received OP-10 once weekly until discontinuation because of progression or adverse events. The efficacy and safety of OP-10 were evaluated in the phase-II part. The tumor objective response rate (ORR), the primary endpoint of the phase-II trial, was assessed through a blinded, independent central review according to RANO-LGG criteria.

Results

A total of 9 (age: 24-72 years) and 31 (age: 4-39 years) patients were administered in the phase-I and phase-II trials, respectively. Although the lower limit of the 90% confidence interval for ORR did not exceed the pre-specified threshold (5%), nine of 31 patients showed tumor regression on T2/FLAIR images. In the phase-II trial, the median OS was 28.4 weeks, and the OS rate at 6 months was 54.8%. Adverse events of grade ≥ 3 were reported in five of 31 (16.1%) patients in the phase-II part, with death of disease, hyperuricemia, malaise, pyrexia, alanine transaminase elevation, and aspartate transaminase elevation.

Conclusion

The results of this study suggested that OP-10 might be efficacious in some patients with recurrent or refractory DMG, without major safety concerns.

Vaginal yolk sac tumor resected by a novel laparo/endoscope-assisted posterior sagittal approach: a case report

Background

Yolk sac tumor (YST) is a germ cell tumor that is generally associated with good prognosis in children. It has been recently reported that vaginal YSTs can be cured using chemotherapy alone. Thus, minimal invasiveness and function preservation are pre-requisites for surgical approaches. Herein, we report a case of vaginal YST that was resected in a function-preserving manner using a unique combination of surgical approaches.

Case presentation

In a 9-month-old Asian female infant, a vaginal tumor was detected while investigating for vaginal bleeding. The patient was referred to our hospital, and the tumor was diagnosed as a YST after incisional biopsy. Six courses of carboplatin-based chemotherapy were administered. Contrary to the findings in previous reports, the tumor was chemo-resistant and surgical resection was required for the residual tumor. During surgery, we utilized laparoscopic and endoscopic procedures to ensure tumor-free surgical margins at the cervix, rectum, and lateral wall of the vagina. Additionally, the posterior sagittal approach was used to easily resect the tumor, and the vagina was reconstructed leaving only inconspicuous scars in the intergluteal cleft. No complications occurred postoperatively. Pathological examination of the surgical specimen revealed tumor-free surgical margins. The patient received four cycles of intensified chemotherapy before and after the surgery. The patient has been disease-free for 6 months now.

Conclusions

Our combination of laparo/endoscopic and posterior sagittal approach ensured a tumor-free macroscopic surgical margin with easier, cosmetically pleasing vaginal reconstruction, while preserving the anorectal and urinary functions. We believe that this approach could be utilized not only for vaginal YST, but also for any vaginal tumor, especially those arising from the posterior or lateral wall.

GCT-19. Toward understanding of the pathogenesis of central nervous system germ cell tumors

Central nervous system germ cell tumors (CNSGCT) are the most enigmatic brain tumors that arise predominantly in children and young adults. CNSGCTs are rare in Europe and North America, while they are rather common in East Asia. The genetic basis of the distinct regional prevalence is yet to be elucidated. The WHO Classification of Central Nervous System Tumours recognizes 6 subtypes of CNSGCT, however multiple subtypes are often present as a mixed tumor, and the subtype may change at the recurrence. In 2012, we organized the Intracranial Germ Cell Tumor Genome Analysis Consortium of Japan (iGCT Consortium) and have collected nearly 300 frozen tumor specimen and patients’ information for CNSGCT cases since then to comprehensively investigate the genomic/epigenomic mechanism of CNSGCT development. We found that alterations of the MAPK and/or PI3K pathways were present in approximately 50% of all subtypes of CNSGCTs, KIT mutations being the most common. Germinomas are characterized by global hypomethylation, indicating that their cell of origin may be primordial germ cells. Transcriptomic profiling suggested that germinomas and non-germinomatous germ cell tumors (NGGCTs) developed from the common cell of origin and then diverted at some stage. We also showed that components of mixed CNSGCT shared the identical somatic mutation while having distinct methylation profiles, supporting the common cell-of-origin theory. In this paper, we will present an overview of our investigation in the iGCT Consortium as well as some of the ongoing projects, single cell RNA sequencing among others.

Quantitative assessment of copy number alterations by liquid biopsy for neuroblastoma

Liquid biopsy, a method of detecting genomic alterations using blood specimens, has recently attracted attention as a non-invasive alternative to surgical tissue biopsy. We attempted quantitative analysis to detect amplification of MYCN (MYCNamp) and loss of heterozygosity at 11q (11qLOH), which are clinical requisites as prognostic factors of neuroblastoma. In this study, cell-free DNA (cfDNA) was extracted from plasma samples from 24 neuroblastoma patients at diagnosis. Copy numbers of MYCN and NAGK genes were quantitatively analyzed by droplet digital PCR (ddPCR). 11qLOH was also assessed by detecting allelic imbalances of heterozygous single nucleotide polymorphisms in the 11q region. The results obtained were compared to those of specimens from tumor tissues. The correlation coefficient of MYCN copy number of cfDNA and tumor DNA was 0.88 (P < 0.00001). 11qLOH was also accurately detected from cfDNA, except for one case with localized NB. Given the high accuracy of liquid biopsy, to investigate components of cfDNA, the proportion of tumor-derived DNA was estimated by examining the variant allele frequency of tumor-specific mutations in cfDNA. The proportion of tumor-derived DNA in cfDNA was 42.5% (range, 16.9%-55.9%), suggesting sufficient sensitivity of liquid biopsy for neuroblastoma. In conclusion, MYCN copy number and 11qLOH could be quantitatively analyzed in plasma cfDNA by ddPCR assay. These results suggest that plasma cfDNA can be substituted for tumor DNA and can also be applied for comprehensive genomic profiling analysis. This article is protected by copyright. All rights reserved.

Dabrafenib + trametinib (dab + tram) in relapsed/refractory (r/r) BRAF V600–mutant pediatric high-grade glioma (pHGG): Primary analysis of a phase II trial

2009

Background: HGGs comprise ≈10% of pediatric central nervous system tumors and are a leading cause of childhood cancer-related death. Overall response rates (ORRs) with current standards of care are low, particularly in the second line, and 2-y overall survival (OS) rates are ≤35%. BRAF V600 mutation is infrequent (≈5% of pHGGs) but associated with improved survival from time of initial diagnosis. In previous trials, dab monotherapy and dab + tram yielded encouraging outcomes in BRAF V600–mutant HGG in pediatric and adult patients (pts), respectively. We describe the results of a Phase II study (NCT02684058) of dab + tram in r/r BRAF V600–mutant pHGG. Methods: Pts aged 1 to <18 y with BRAF V600–mutant HGGs and Karnofsky/Lansky performance status ≥50% who had failed first-line therapy were enrolled in a single-arm cohort. Pts received dab twice daily (<12 y, 5.25 mg/kg/d; ≥12 y, 4.5 mg/kg/d) + tram once daily (<6 y, 0.032 mg/kg/d; ≥6 y, 0.025 mg/kg/d). The primary endpoint was ORR (independent review; HGG-RANO criteria); secondary endpoints included ORR (investigator review), duration of response (DOR), progression-free survival (PFS), OS, and safety. Results: A total of 41 pts with diverse WHO Grade III/IV gliomas were enrolled; median time since diagnosis was 17.4 mo (range, 2.7-174.3 mo), and most had prior surgery (97.6%), radiotherapy (90.2%), and/or systemic antineoplastic therapy (80.5%). At data cutoff (August 23, 2021; median follow-up, 25.1 mo), 21 pts (51.2%) remained on treatment; most discontinuations (16 of 20) were due to progressive disease. Median exposure was 72.7 wk (range, 1.3-172.1 wk). The primary endpoint was met, with an independently assessed ORR of 56.1% (95% CI, 39.7%-71.5%). Median DOR was 22.2 mo (95% CI, 7.6 mo-not estimable [NE]; 12-mo Kaplan-Meier [KM] DOR rate, 62.2%), and median PFS was 9.0 mo (95% CI, 5.3-24.0 mo; 12-mo KM PFS rate, 44.1%). There were 14 deaths (34.1%), with 12 due to HGG and 2 due to serious adverse events (AEs; encephalomyelitis and intracranial pressure increased [n = 1 each], not treatment related per investigators); median OS was 32.8 mo (95% CI, 19.2 mo-NE; 12-mo KM OS rate, 76.3%). The most common all-cause AEs were pyrexia (51.2%), headache (34.1%), dry skin (31.7%), vomiting (29.3%), and diarrhea (24.4%). Two pts (4.9%) had AEs leading to discontinuation (both rash), and 26 (63.4%) had AEs leading to dose modification. Conclusions: Treatment with dab + tram demonstrated an improvement in ORR, response durability, and survival compared with estimates based on historical observations with current treatment approaches in r/r BRAF V600–mutant pHGG. Safety was consistent with the established profile of dab + tram in other indications. Thus, dab + tram may represent a critical treatment advance for this pt population with high unmet need. Clinical trial information: NCT02684058.

Trial in progress: A phase I trial of dual EZH 1/2 inhibitor valemetostat tosylate (DS-3201b) in pediatric, adolescent, and young adult patients with malignant solid tumors

TPS10059

Background: Enhancer of zeste homolog enzymes (EZH1 and EZH2) form parts of the polycomb repressive complex 2 and regulate gene expression by catalyzing the tri-methylation of lysine 27 residue of histone H3. SMARCB1/INI1 is one of the core components of the SWI/SNF chromatin remodeling complex, with the loss of SMARCB1/INI1 causing the oncogenic activation of EZH2 and EZH1. The inhibition of EZH2 or both EZH2 and EZH1 can be effective against various hematological malignancies and SMARCB1/INI1-deficient solid tumors. Valemetostat tosylate (DS-3201b; valemetostat) is a potential first-in-class dual inhibitor of EZH1 and EZH2 that targets epigenetic regulations by inhibiting both EZH1 and EZH2 enzymes. A phase 2 single-arm study showed that valemetostat demonstrated promising response rates in Japanese patients with relapsed or refractory adult T-cell leukemia/lymphoma (Yoshimitsu M et al., presented at ASH Annual Meeting, 2021). Tumors characterized by SMARCB1/INI1 deficiency (a SWI/SNF mutation), such as malignant rhabdoid tumors, epithelioid sarcoma, or synovial sarcoma are quite frequently observed during childhood and adolescence, among whom valemetostat is expected to show antitumor effects. Methods: This open-label multi-center phase I trial evaluates the safety and efficacy of valemetostat in pediatric, adolescent, and young adult patients with refractory/relapsed solid tumors. The inclusion criteria are relapsed, refractory, or progressive metastatic disease; >3 and <19 years of age during the dose escalation cohort and < 29 years of age in the expanded cohort; performance status of >50 (assessed by Karnofsky Performance score in patients >16 years old, and Lansky Performance score in patients <15 years old); and adequate organ function. Valemetostat is administered orally once a day without interruption. Three dose levels (150, 200, and 250 mg/1.7 m2) are assessed using a 3+3 design during the dose escalation cohort. After determining the recommended phase 2 dose (RP2D) during dose escalation cohort, up to 30 patients will be further enrolled, and the safety and efficacy data of valemetostat are determined in the expanded cohort. The primary endpoint is the incidence of dose limiting toxicity, whereas the secondary endpoints include safety, pharmacokinetics, overall response rate, progression-free survival. The overall response rate of the tumors with SMARCB1/INI1 deficiency or SWI/SNF mutation is also evaluated as a secondary endpoint. Exploratory endpoint includes overall survival. Enrollment into this trial began in March 2020, and enrollment into the dose escalation cohort was completed. Enrollment into the expanded cohort began in November 2021. Clinical Trial Information: jRCT2031190268.

Gemtuzumab Ozogamicin Followed by Unrelated Cord Blood Transplantation With Reduced-intensity Conditioning for a Child With Refractory Acute Promyelocytic Leukemia

There is no established treatment for patients with acute promyelocytic leukemia (APL) refractory to targeted therapies with all-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO). We report here a case of an 8-month-old girl with APL who failed standard ATRA-combined chemotherapy. Although molecular remission was achieved after introducing ATRA/ATO combination therapy, molecular relapse occurred during the ATO consolidation courses. Subsequent molecular remission was rapidly achieved after administering 2 doses of gemtuzumab ozogamicin. She was successfully treated with unrelated cord blood transplantation using reduced-intensity conditioning. Gemtuzumab ozogamicin might be a preferable choice for patients with APL refractory to standard therapy.

HSP90 inhibition overcomes resistance to molecular targeted therapy in BRAFV600E mutant high-grade glioma

PURPOSE

Molecular targeted therapy using BRAF and/or MEK inhibitors has been applied to BRAFV600E mutant high-grade gliomas (HGGs); however, the therapeutic effect is limited by the emergence of drug resistance.

EXPERIMENTAL DESIGN

We established multiple paired BRAFV600E mutant HGG patient-derived xenograft (PDX) models based on tissues collected prior to and at relapse after molecular targeted therapy. Using these models, we dissected treatment resistant mechanisms for molecular targeted therapy and explored therapeutic targets to overcome resistance in BRAFV600E HGG models in vitro and in vivo.

RESULTS

We found that, despite causing no major genetic and epigenetic changes, BRAF and/or MEK inhibitor treatment deregulated multiple negative feedback mechanisms, which led to the re-activation of the MAPK pathway through c-Raf and AKT signaling. This altered oncogenic signaling primarily mediated resistance to molecular targeted therapy in BRAFV600E mutant HGG. To overcome this resistance mechanism, we performed a high-throughput drug screening to identify therapeutic agents that potently induce additive cytotoxicity with BRAF and MEK inhibitors. We discovered that HSP90 inhibition combined with BRAF/MEK inhibition coordinately deactivated the MAPK and AKT/mTOR pathways, and subsequently induced apoptosis via dephosphorylation of GSK3β (Ser9) and inhibition of Bcl-2 family proteins. This mediated potent cytotoxicity in vitro and in vivo in refractory models with acquired resistance to molecular-targeted therapy.

CONCLUSIONS

The combination of an HSP90 inhibitor with BRAF or MEK inhibitors can overcome the limitations of the current therapeutic strategies for BRAFV600E mutant HGG.

PEDT-9 A study of NovoTTF-100A to expand the regulatory indication for childhood glioblastoma through a pediatric clinical trial based on the Advanced Medical Care system

Background: Tumor-treating fields (TTF) are alternating electric fields applied continuously to the brain by attaching 2-pair arrays on the scalp. Although TTF therapy has demonstrated efficacy against supratentorial glioblastoma (GBM) in adults, its safety and efficacy in children have not been confirmed. In Japan, off-label use of medical devices is almost impossible because the national health insurance system does not cover the cost of off-label use of drugs and medical devices. Therefore, TTF therapy cannot be applied to the treatment of pediatric GBM.

[Objectives] The investigator-initiated clinical trial aims to expand regulatory approval of TTF therapy for pediatric GBM treatment based on safety and exploratory efficacy data.

Methods: Patients aging between 5 and 17 years with histopathological diagnosis of GBM (either newly diagnosed or first-recurrence), which located in the supratentorial region would be included. All the patients will receive TTF therapy for 28 days per course for up to 26 courses until the end-of-therapy criteria are met. The primary endpoint is the adverse event rate with causality. The secondary endpoints include various time-to-event measures and QoL. In total ten patients will be enrolled.

Current Status: Discussions with the Pharmaceuticals and Medical Devices Agency (PMDA) led to a tentative consensus that the accumulated data on the efficacy of NovoTTF-100A for adult GBM may be extrapolatable to pediatric GBM if the trial is able to demonstrate efficacy equivalent to that found in previous, adult studies. On the other hand, the combination of the pediatric safety data gathered in this trial and the findings of international studies, including clinical trials and post-marketing surveillance studies, may expedite approval of the device for pediatric GBM treatment. The trial started patient enrollment in April, 2021 with the supervision of the Advanced Medical Care administration system and is currently awaiting the first eligible patient.

PEDT-5 Problem for the guideline of CNS germ cell tumors

Primary CNS germ cell tumors (GCTs) are rare neoplasms, therefore, a clinical guideline has not been established so far. While better management has been achieved over recent decades by modifying radiation coverage and selecting appropriate chemotherapy, standardization of treatment remains challenging, partly due to the low volume of cases encountered in each institution. As the incidence is higher in East Asia, including Japan, the Japan Society for Neuro-Oncology established a multidisciplinary task force to create an evidence-based guideline for CNS GCTs. The Medical Information Network Distribution Service (Minds) guideline was referred to and utilized in the course of creating this guideline. We chose 6 topics and 10 clinical questions. This guideline provides recommendations for multiple dimensions of clinical management for CNS GCTs, with particular focus on diagnostic measures including serum markers, treatment algorithms including surgery, radiotherapy and chemotherapy, and under-investigated but important areas such as treatment for recurrent cases, long-term follow-up protocols and long-term sequelae. International collaborations to set standards of clinical management for this rare tumor have proven fruitful, concurrently, many fields continue to show variance in clinical practice, partly due to the rarity of clinical encounters and the absence of documented standards. There still seem to be differences in the treatment concept between Japan and North America or Europe countries. This guideline serves the purpose of helping healthcare professionals keep up to date with current knowledge and standards of management for patients with this rare disease in daily clinical practice, as well as driving future translational and clinical research by recognizing unmet needs concerning this tumor. We discuss about the issues both already clarified and should be cleared in the future.

The Japan Society for Neuro-Oncology Guideline on the Diagnosis and Treatment of Central Nervous System Germ Cell Tumors

Primary CNS germ cell tumors (GCTs) are rare neoplasms predominantly observed in the pediatric and young adult populations. In line with the hypothesis that the primordial germ cell is the cell-of-origin, histopathological examinations for this pathology involve a diverse range of components mirroring the embryogenic developmental dimensions. Chemotherapy and radiotherapy are the mainstays of treatment, with surgery having a limited role for diagnosis and debulking of residual tissue after treatment. While better management has been achieved over recent decades by modifying radiation coverage and selecting appropriate chemotherapy, standardization of treatment remains challenging, partly due to the low volume of cases encountered in each institution. As the incidence is higher in East Asia, including Japan, the Japan Society for Neuro-Oncology established a multidisciplinary task force to create an evidence-based guideline for CNS GCTs. This guideline provides recommendations for multiple dimensions of clinical management for CNS GCTs, with particular focus on diagnostic measures including serum markers, treatment algorithms including surgery, radiotherapy and chemotherapy, and under-investigated but important areas such as treatment for recurrent cases, long-term follow-up protocols and long-term sequelae. This guideline serves the purpose of helping healthcare professionals keep up to date with current knowledge and standards of management for patients with this rare disease in daily clinical practice, as well as driving future translational and clinical research by recognizing unmet needs concerning this tumor.

Necessity for craniospinal irradiation of germinoma with positive cytology without spinal lesion on MR imaging-A controversy

Background

Cerebrospinal fluid (CSF) cytology and spinal MR imaging are routinely performed for staging before treatment of intracranial germinoma. However, the interpretation of the results of CSF cytology poses 2 unresolved clinical questions: (1) Does positive CSF cytology correlate with the presence of spinal lesion before treatment? and (2) Is craniospinal irradiation (CSI) necessary for patients with positive CSF cytology in the absence of spinal lesion?

Methods

Multicenter retrospective analyses were performed based on a questionnaire on clinical features, spinal MR imaging finding, results of CSF cytology, treatments, and outcomes which was sent to 86 neurosurgical and 35 pediatrics departments in Japan. Pretreatment frequencies of spinal lesion on MR imaging were compared between the patients with positive and negative cytology. Progression-free survival (PFS) rates were compared between patients with positive CSF cytology without spinal lesion on MR imaging treated with CSI and with whole brain or whole ventricular irradiation (non-CSI).

Results

A total of 92 germinoma patients from 45 institutes were evaluated by both CSF cytology and spinal MR images, but 26 patients were excluded because of tumor markers, the timing of CSF sampling or incomplete estimation of spinal lesion. Of the remaining 66 germinoma patients, spinal lesions were equally identified in patients with negative CSF cytology and positive cytology (4.9% and 8.0%, respectively). Eleven patients treated with non-CSI had excellent PFS comparable to 11 patients treated with CSI.

Conclusion

CSI is unnecessary for germinoma patients with positive CSF cytology without spinal lesions on MR imaging.

[Pediatric Glioma]

Pediatric gliomas include various types of glioma broadly categorized as low- or hi-grade based on histopathological features. Clinically significant types include cerebellar astrocytomas, optic pathway / hypothalamic pilocytic astrocytomas, and brainstem gliomas. Neurosurgical roles vary for different kinds of pediatric gliomas. Since these representative tumors remain rare, the patients should be directed toward facilities with experienced neurosurgeons. Radiotherapy and chemotherapy are very important as either adjuvant or primary treatment modalities. Recent advancements in molecular biology have revealed unique genetic aberrations in different types of pediatric gliomas. The RAS/MAPK pathway anomalies, including BRAF-KIAA1549 fusion and BRAF V600E mutation, are present in most low-grade gliomas. BRAF/MEK-inhibitors have yielded promising clinical study results. Diffuse midline gliomas, including diffuse intrinsic pontine gliomas, often harbor H3 mutations such as H3K27M. Agents that target these molecular aberrations are unavailable. Because gliomas in infants are sub-categorized by their genetic abnormalities, novel agents targeting ALK, ROS1, or NTRK fusions are promising treatments.

Proton beam therapy for children and adolescents and young adults (AYAs): JASTRO and JSPHO Guidelines

Children and adolescents and young adults (AYAs) with cancer are often treated with a multidisciplinary approach. This includes use of radiotherapy, which is important for local control, but may also cause adverse events in the long term, including second cancer. The risks for limited growth and development, endocrine dysfunction, reduced fertility and second cancer in children and AYAs are reduced by proton beam therapy (PBT), which has a dose distribution that decreases irradiation of normal organs while still targeting the tumor. To define the outcomes and characteristics of PBT in cancer treatment in pediatric and AYA patients, this document was developed by the Japanese Society for Radiation Oncology (JASTRO) and the Japanese Society of Pediatric Hematology/Oncology (JSPHO).

Tumor-Treating Fields Therapy for Pediatric Brain Tumors

Tumor-treating fields (TTFields) are alternating electric fields applied continuously to the brain by attaching two-pair arrays on the scalp. Although TTFields therapy has demonstrated efficacy against supratentorial glioblastoma (GBM) in adults, its safety and efficacy in children have not been confirmed. Despite differences in the genetic etiology of the adult and pediatric forms of GBM, both have certain clinical behaviors in common, allowing us to test TTFields therapy in pediatric GBM. Recently, several, pediatric case-series using TTFields therapy have been published, and a few, prospective, pediatric studies are ongoing. Because GBMs are extremely rare in pediatric patients, where they comprise a wide variety of genetic subtypes, these pediatric studies are feasibility studies targeting various types of malignant brain tumor. Although they are important for confirming the safety and feasibility of TTFields therapy in the pediatric population, confirming its efficacy against each type of pediatric brain tumor, including the GBM, is difficult. Our clinical research team, therefore, planned an investigator-initiated clinical trial targeting pediatric supratentorial GBMs (as in adults) with the aim of expanding regulatory approval of TTFields therapy for pediatric GBM treatment based on safety and exploratory efficacy data in combination with the accumulated evidence on adult GBMs.

Initial symptoms and diagnostic delay in children with brain tumors at a single institution in Japan

Background

A prolonged interval between onset of symptoms and diagnosis of childhood brain tumor is associated with worse neurological outcomes. The objectives of this study are to determine factors contributing to diagnostic delay and to find an interventional focus for further reduction in the interval between symptom onset and diagnosis in Japan.

Methods

We retrospectively analyzed 154 patients younger than 18 years with newly diagnosed brain tumors who visited our institution from January 2002 to March 2013.

Results

The median age at diagnosis was 6.2 years and the median total diagnostic interval (TDI) was 30 days. Patients with low-grade tumors and cerebral midline tumor location had significantly long TDI. Durations between the first medical consultation and diagnosis (diagnostic interval, DI) were exceedingly longer for patients with visual, hearing, or smelling abnormalities as the first symptom (median, 303 days). TDI and DI of patients who visited ophthalmologists or otolaryngologist for the first medical consultation were significantly longer. Among these patients, longer DI was associated with worse visual outcome.

Conclusion

Raising awareness of brain tumor diagnosis among ophthalmologists and otolaryngologists may reduce diagnostic delay and may improve the neurological impairment of children with brain tumors in Japan.

So-called bifocal tumors with diabetes insipidus and negative tumor markers: are they all germinoma?

BACKGROUND

The Delphi consensus statements on the management of germ cell tumors (GCTs) failed to reach agreements on the statement that the cases with (i) pineal and neurohypophyseal bifocal lesion, (ii) with diabetes insipidus, and (iii) with negative tumor markers can be diagnosed as germinoma without histological verification. To answer this, multicenter retrospective analysis was performed.

METHODS

A questionnaire on clinical findings, histological diagnosis, and details of surgical procedures was sent to 86 neurosurgical and 35 pediatrics departments in Japan.

RESULTS

Fifty-one institutes reported 132 cases that fulfilled the 3 criteria. Tissue sampling was performed in 91 cases from pineal (n = 44), neurohypophyseal (n = 32), both (n = 6), and distant (n = 9) lesions. Histological diagnosis was established in 89 cases: pure germinoma or germinoma with syncytiotrophoblastic giant cells in 82 (92.1%) cases, germinoma and mature teratoma in 2 cases, and granulomatous inflammation in 2 cases. Histological diagnosis was not established in 2 cases. Although no tumors other than GCTs were identified, 3 (3.4%) patients had non-germinomatous GCTs (NGGCTs). None of the patients developed permanent complications after endoscopic or stereotactic biopsy. Thirty-nine patients underwent simultaneous procedure for acute hydrocephalus without permanent complications, and hydrocephalus was controlled in 94.9% of them.

CONCLUSION

All patients who fulfilled the 3 criteria had GCTs or granulomatous inflammation, but not other types of tumors. However, no fewer than 3.4% of the patients had NGGCTs. Considering the safety and the effects of simultaneous procedures for acute hydrocephalus, biopsy was recommended in such patients.

GCT-73. EXPRESSION PROFILING OF INTRACRANIAL GERM CELL TUMORS REVEALS UPREGULATION OF RAS THROUGH mRNA-microRNA SIGNALING PATHWAY

Intracranial germ cell tumors (IGCTs) account for 3% of CNS tumors in children in the U.S. and 11% in Japan and East Asian countries. IGCTs are separated into two distinct subtypes based on histology: germinomas and non-germinomatous germ cell tumors (NGGCTs). The deep central location of IGCTs makes surgical resection and therefore molecular subtype classification difficult, and previous gene expression studies are limited. We performed mRNA expression profiling (Human Genome U133 Plus 2.0) and microRNA expression profiling (ABI TaqMan) with 36 and 49 IGCTs, respectively. Sample stratification using non-negative matrix factorization clustering of gene expression revealed two distinct subgroups that delineated germinomas from NGGCTs. Employing stepwise model building in each data set separately, we were able to separate these groups using only mRNA probes for the LIN28B and L1TD1 genes, and two microRNA, microRNA-26a and microRNA-373. MicroRNA26a suppresses the LIN28B gene and is down-regulated in germinoma. LIN28B directly binds and suppresses the let-7 microRNA family, which suppress the KRAS oncogene, previously found to be mutated in ~19% of IGCTs. L1TD1 is required for human stem cell renewal and directly interacts with LIN28B for its RNA binding function. LIN28B and L1TD1 are both known to be upregulated in other systemic germ cell tumors, but this has not yet been documented in IGCTs. In conclusion, these results show that intracranial germinomas have similar gene expression compared to systemic seminoma, and suggest a mechanism by which activation of LIN28B and L1TD1 downregulates the let-7 microRNA and subsequently upregulates KRAS.

ATRT-11. PREVALENCE OF GERMLINE VARIANTS IN SMARCB1 INCLUDING SOMATIC MOSAICISM IN AT/RT AND OTHER RHABDOID TUMORS

BACKGROUND

Genetic hallmark of atypical teratoid/rhabdoid tumor (AT/RT) is loss-of-function variants or deletions in SMARCB1 gene on 22q11.2 chromosome, which is common to extracranial malignant rhabdoid tumors (MRT). Previous studies demonstrated that approximately one-thirds of AT/RT and extracranial MRT patients harbored germline SMARCB1 variants as the rhabdoid tumor predisposing syndrome. We studied herein intensive analysis of the SMARCB1 gene in AT/RT and extracranial MRT patients focusing on prevalence of germline genetic variants. PROCEDURE: In total, 16 patients were included. Both tumor-derived DNA and germline DNA were obtained from all patients. First, screening for SMARCB1 alterations in the tumor specimens was done by direct sequencing, ddPCR and SNP array analysis. Then, analysis of germline DNA samples focusing on the genomic abnormalities detected in the paired tumors in each case was performed.

RESULTS

In eight of 16 cases (50%), genomic alterations observed in the tumor-derived DNA were also detected in the germline DNA. It is worth noting that three patients had germline mosaicism. Two of three patients had mosaic deletion, including SMARCB1 region, and the average copy number of the deleted region in the SMARCB1 gene in the germline was 1.60 and 1.76. For another patient, the fraction of SMARCB1 variants in normal cells was as low as 1.7%.

CONCLUSIONS

Approximately half the MRT cases in this study had SMARCB1 germline alterations. Considering the presence of low-frequency mosaicisms which conventional methods might overlook, inherited germline variants in predisposition genes are more important than previously assumed for the pathogenesis of pediatric cancers.

RARE-16. SEVEN CASES OF RETINOBLASTOMA WITH CNS INVOLVEMENTS

Treatment strategy for trilateral retinoblastoma (TRb: very rare RB with brain tumor) or retinoblastoma with central nervous system (CNS) involvement is not established yet. We retrospectively reviewed our seven cases of these rare almost fatal tumors. Their ages at diagnosis are 0y3m-1y10m (median 1y3m) (Male 4, Female 3). Only one had RB family history. Their affected eyes were bilateral 3, unilateral 3 and no 1. Their CNS involvements were suprasellar tumor 4, pineal tumor 1 and cerebrospinal fluid (CSF) cytology positive 2. Three of the suprasellar tumor patients had spinal metastasis. Four of the seven patients were TRb and one were genetically classified suprasellar retinoblastoma. All of them were treated with chemotherapy and four received high-dose chemotherapy. Three brain tumors of four TRb almost disappeared with chemotherapy. Two of them also received radiotherapy but relapsed. Although one radiation-free long-term TRb survivor developed secondary osteosarcoma, he got remission again and live 5 more years. One CSF positive Rb patient with chiasm invasion died of disease 11 months later. The other patient had no chiasm invasion nor CSF involvement at diagnosis, but his CSF cytology turned to positive after his second cycle of chemotherapy. He got remission with radiotherapy and high-dose chemotherapy, and alive without disease for 4 years. 2-year RFS and 2-year OS of all patients were 40% and 60%. Although our TRb patients responded to chemotherapy, it was difficult to avoid radiotherapy except one. Data accumulation is necessary for better treatment of these cancer-predisposed patients.

ETMR-11. A CASE OF PRIMARY DIFFUSE LEPTOMENINGEAL PRIMITIVE NEUROECTODERMAL TUMOR

BACKGROUND

Primary diffuse leptomeningeal primitive neuroectodermal tumor (PDL PNET) is a rare embryonal brain tumor which arises primarily in the meninges without an intraparenchymal mass. Few previous reports of this condition exist, and the clinical outcomes are poor. We herein report a case of a child with PDL PNET and present a cursory review of the literature. CASE: A 3-year-old female patient was seen at a local clinic due to vomiting, headaches, and seizures. As a head MRI revealed hydrocephalus but no mass, acute encephalopathy was initially diagnosed. She received steroid pulse therapy, but the symptoms progressed to hallucination and lethargy. Another MRI at the 1-month follow-up revealed diffuse leptomeningeal enhancement. Thereafter she was transferred to our hospital. A spine MRI revealed spinal dissemination. She underwent a dura mater biopsy, and the pathological analysis led to the diagnosis of PDL PNET. She received chemotherapy consisting of vincristine, cyclophosphamide, etoposide, cisplatin, and intrathecal methotrexate injections two months after the initial presentation. The progressive hydrocephalus was managed with external ventricular drainage. Two weeks after the first cycle of chemotherapy the hydrocephalus resolved, and the external ventricular drainage was removed. A follow-up MRI showed that the leptomeningeal enhancement decreased during the four cycles of chemotherapy without radiotherapy. The patient is scheduled to receive high-dose chemotherapy as consolidation therapy.

CONCLUSION

PDL PNET is extremely rare, and its diagnosis is often delayed. Treatment of PDL PNET is very difficult due to its aggressive course, and surgical resection is impossible. Early diagnosis may help improve outcomes.

HGG-49. A PEDIATRIC THALAMIC HIGH-GRADE GLIOMA WITH H3F3A K27M AND BRAF V600E DOUBLE MUTATIONS

CASE

A 18-month-old boy presented with approximately 2 months history of progressive left hemiparesis and left exotropia. MRI study showed a 3–4 cm T1-iso, T2-high tumor at right thalamus to midbrain with little contrast enhancement. The patient underwent endoscopic biopsy of the tumor, which showed relatively dense proliferation of small cells with round nuclei, mitosis of the tumor cell, but no necrosis. Immunohistochemical showed positive stain of GFAP and Olig2. Ki-67 was 34%. The histopathological diagnosis was compatible with high grade glioma. Chemotherapy with vincristine, cyclophosphamide, cisplatin and etoposide was initiated. Molecular testing of the tumor revealed H3F3A K27M and BRAF V600E double mutations in DNA from frozen tumor tissue.

DISCUSSION

The concurrent mutation of H3F3A K27M and BRAF V600E in pediatric glioma is very rare, but there are several cases previously reported in literature. Interestingly those cases are heterogenous in age, location, histopathological subtypes and clinical outcome.

SURG-17. CLINICAL CHARACTERISTICS AND OUTCOMES OF EPILEPSY-RELATED BRAIN TUMOR IN CHILDREN

OBJECTIVE

Epilepsy is one of the earliest symptoms in pediatric brain tumor. Gross total resection (GTR) of the tumor does not necessarily achieve seizure free, therefore it is controversial whether surrounding epileptic foci should be resected at the initial surgery. The aims of this study are to report clinical characteristics and outcome of pediatric epilepsy-related brain tumor (ERBT) and to discuss treatment strategy.

METHODS

Subjects were children less than 18 years old who underwent surgery for ERBT. Patients in whom epilepsy had been controlled before surgery were excluded. Data were collected from medical record and retrospectively reviewed.

RESULTS

Twenty-one children (8 boys and 13 girls) were analyzed in this study. The mean age at surgery was 6.8 years. Tumor was astrocytic tumor in 10, gangliogioma in 4 and dysembryoplastic neuroepithelial tumor in 3. Intracranial subdural electrodes were placed prior to tumor resection in 5 cases. GTR was achieved in 14 (67%). Seizure free was achieved in 15 (71.4%). GTR was significantly associated with seizure free (p=0.002).

CONCLUSION

In most of ERBT, seizure free can be achieved by lesionectomy alone. However, the resection of surrounding epileptic foci is required in some cases. Detailed examinations to detect the epileptic foci should be performed in ERBT, particularly in case of drug-resistant intractable epilepsy.

The local structure of self-doped BiS2-based layered systems as a function of temperature

We have studied the local structure of layered Eu(La,Ce)FBiS2 compounds by Bi L3-edge extended X-ray absorption fine structure (EXAFS) measurements as a function of temperature. We find that the BiS2 sub-lattice is largely distorted in EuFBiS2, characterized by two different in-plane Bi-S1 distances. The distortion is marginally affected by partial substitutions of Ce (Eu0.5Ce0.5FBiS2) and La (Eu0.5La0.5FBiS2). The temperature dependence of the local structure distortion reveals an indication of possible charge density wave like instability in the pristine self-doped EuFBiS2 and Ce substituted Eu0.5Ce0.5FBiS2 while it is suppressed in La substituted Eu0.5La0.5FBiS2. In compounds with higher superconducting transition temperature, the axial Bi-S2 bond distance is elongated and the related bond stiffness decreased, suggesting some important role of this in the charge transfer mechanism for self-doping in the active BiS2-layer. In-plane Bi-S1 distances are generally softer than the axial Bi-S2 distance and they suffer further softening by the substitutions. The results are discussed in relation to an important role of the Bi defect chemistry driven asymmetric local environment in the physical properties of these materials.

Neoadjuvant chemotherapy for atypical teratoid rhabdoid tumors (AT/RTs)

PURPOSE

Atypical teratoid rhabdoid tumor (AT/RT) is a rare, clinically highly malignant tumor. The extent of the surgical resection may affect survival. However, it is often difficult to perform gross total resection (GTR) at an initial surgery because of the large tumor size and high vascularity. Neoadjuvant chemotherapy may reduce not only the size but also the vascularity. We report our experience, review the literature, and analyze its effectiveness.

METHODS

A retrospective chart review of patients who underwent neoadjuvant chemotherapy and second-look surgery was performed. Demographic data, treatment courses, changes in tumor after the chemotherapy, extent of resection and estimated blood loss (EBL) during the second-look surgery, and outcome of each children were evaluated.

RESULTS

There are 4 cases. The average age at diagnosis was 13.3 months (2-30 months). Two to 4 courses of neoadjuvant chemotherapy were performed. MRI after the chemotherapy showed reduction of tumor volume, and tumor vascularity at the second-look surgery decreased in all cases. GTR was achieved in 3 cases, and NTR in 1 case. The mean EBL/estimated blood volume (EBL/EBV) was 21.3% (1.5-39%). The mean follow-up period was 23 months (2-48 months). At the last follow-up, 2 patients were alive without recurrence of the tumor (the follow-up periods were 48 and 16 months).

CONCLUSIONS

Neoadjuvant chemotherapy for AT/RTs might reduce both tumor size and vascularity, which enabled the maximal tumor resection. It may contribute to improve the prognosis of AT/RT through facilitating the tumor resection.

Tacrolimus blood concentration increase depends on administration route when combined with voriconazole in pediatric stem cell transplant recipients

BACKGROUND

Understanding of TAC pharmacokinetics is required to avoid both overdosing and underdosing. VRCZ is known to increase the TAC blood concentration by inhibiting CYP3A4; however, detailed, practical information on pediatric cases is still scarce. Herein, we investigated the association between the TAC blood concentration and dosage focusing on the administration route and concomitant use of VRCZ in children.

METHODS

In total, 38 children who received TAC during stem cell transplantation at our hospital between January 2013 and April 2018 were included. The ratio of the TAC blood concentration (ng/mL) to dosage (mg/kg/day) (C/D) was calculated at the last continuous intravenous infusion (C/Div) and after switching to oral administration (C/Dpo).

RESULTS

Patients with VRCZ (n = 14) showed a higher C/D regardless of administration route (median C/Div: with VRCZ/without VRCZ = 832/643, median C/Dpo: with VRCZ/without VRCZ = 339/45). Additionally, the (C/Div)/(C/Dpo) was about one-fourth in cases with VRCZ; the median (C/Div)/(C/Dpo) was 3.3 for cases with VRCZ and 13.5 for cases without VRCZ. Interestingly, the increase in the TAC blood concentration due to VRCZ was higher when TAC was administered orally, especially in adolescent patients.

CONCLUSIONS

To obtain an optimal TAC blood concentration, dose adjustment based on multiple factors, such as administration route, concomitant use of VRCZ, and age, is required.

PEDT-04 SIX CASES OF RETINOBLASTOMA WITH CNS INVOLVEMENT

Although the survival rate of intraocular retinoblastoma (RB) is nearly 100%, the outcome of central nervous system (CNS) involvement or Trilateral retinoblastoma (TRb: very rare RB which associated with brain tumor) is dismal. We retrospectively reviewed our six cases of these rare tumors. Their ages at diagnosis are 0y3m-1y10m (median 1y3m) (Male 4, Female 2). Only one had RB family history. Their affected eyes were bilateral 2, unilateral 3 and no 1. Their CNS diseases were suprasellar tumor 3, pineal tumor 1 and cerebrospinal fluid (CSF) cytology positive 2. Two of the suprasellar tumor patients had spinal metastasis. Three of the six patients were TRb. One TRb patient was treated with chemotherapy and high-dose chemotherapy without radiotherapy. Although he suffered with secondary osteosarcoma seven years later, he got complete remission and alive 5 years more without any tumor recurrence. The second TRb patient was treated with chemotherapy and local radiotherapy but relapsed 20 months later. The third TRb patient was chemotherapy resistant. Two CSF positive patients had optic nerve invasion. One patient with chiasm invasion died 11 months later because of treatment resistance. The other patient with optic nerve invasion before optic canal had no CNS tumor nor CSF involvement at diagnosis. Chemotherapy before enucleation was given to avoid dissemination. However, CSF cytology became positive after enucleation and remained even with intensified chemotherapy. Finally, he got remission with radiotherapy and high-dose chemotherapy, and alive without disease for 3.8 years. The last patient had suprasellar genetically classified retinoblastoma tumor and cerebrospinal metastasis. This patient showed good chemotherapy response and is still under treatment. Even with &quotso called° fatal RB cases, some case could survive with intensified therapy. Data accumulation is necessary for better survival of these tumors.

Clinical characteristics, treatment, and survival outcome in pediatric patients with atypical teratoid/rhabdoid tumors: a retrospective study by the Japan Children's Cancer Group

OBJECTIVE

The prognosis of atypical teratoid/rhabdoid tumors (ATRTs) has improved in recent years with the use of multimodal therapy, mainly in cases not involving metastatic disease. The authors wanted to obtain historical control data and evaluate the suitable treatments in Japanese children with ATRTs that were proven negative for INI-1 immunostaining.

METHODS

The authors retrospectively collected clinical information on 38 pediatric patients with ATRTs treated from 2005 to 2016 and analyzed the data for this series.

RESULTS

The median age of the patient population was 1.3 years, and the male/female ratio was approximately 2:1. Twenty-three patients (60.5%) had metastases. The effects of treatment on prognosis were analyzed for 34 patients after exclusion of 4 patients who could not receive curative treatment. At a median follow-up of 40.9 months, the mean (± SD) progression-free survival (PFS) and overall survival (OS) were 66.6% ± 8.3% and 45.9% ± 8.7% at 2 years and 44.2% ± 9.9% and 34.2% ± 8.9% at 5 years, respectively. The metastasis stage at diagnosis (M0-1 vs M2-4) (HR 2.68, 95% CI 1.08-6.65; p = 0.0338) and gross tumor resection (yes vs no) (HR 3.49, 95% CI 1.01-12.1; p = 0.0481) were prognostic factors for PFS but not for OS. Postoperative chemotherapy was performed in all 34 cases. High-dose chemotherapy was performed in 19 (55.8%) of 34 patients and showed a positive impact on OS (HR 0.31, 95% CI 0.11-0.86; p = 0.0254); the most commonly used regimen was a double-conditioning regimen of thiotepa plus melphalan. Local radiotherapy had a positive impact on both PFS and OS; however, craniospinal irradiation (CSI) performed in 12 patients as the primary therapy was associated with a poor outcome. Disseminated recurrence within 12 months from diagnosis was the most common pattern of treatment failure regardless of CSI.

CONCLUSIONS

There has been an improvement in outcomes for pediatric ATRT patients since the introduction of multimodal therapy in Japan, mainly in patients without metastases. Even if selection bias is taken into consideration, CSI did not contribute to an improved prognosis. Novel treatment approaches are required for pediatric ATRT patients with metastases.

Temperature dependent local atomic displacements in NaSn2As2 system

NaSn₂As₂ is mechanically exfoliable layered van der Waals (vdW) Zintl phase that is getting interesting due to its low thermal conductivity and recently observed superconductivity. Here, we have investigated the temperature dependent local structure of NaSn₂As₂ by a combined analysis of As K-edge and Sn K-edge extended x-ray absorption fine structure measurements. The system is intrinsically disordered with the interatomic distances largely consistent to those estimated by average structure measurements. The stretching force constants of different bond distances have been determined using temperature dependent mean square relative displacements. The Sn-As distance is the strongest bond in this system, having covalent nature, unlike the weaker interlayer distances which are characterized by vdW type bonding. Among them, As-Na distance is slightly weaker than Sn-Sn(i) below  ∼200 K and tends to get stronger above this temperature. The anomalous behavior of As-Na bond suggests that the mechanical exfoliation in this system is likely to be temperature dependent. The anomaly in the interlayer atomic correlations may be due to a charge density wave-like instability around this temperature, indicated by earlier experiments. The local structure and disorder are discussed in relation to the physical properties of NaSn₂As₂.

Alterations in ALK/ROS1/NTRK/MET drive a group of infantile hemispheric gliomas

Infant gliomas have paradoxical clinical behavior compared to those in children and adults: low-grade tumors have a higher mortality rate, while high-grade tumors have a better outcome. However, we have little understanding of their biology and therefore cannot explain this behavior nor what constitutes optimal clinical management. Here we report a comprehensive genetic analysis of an international cohort of clinically annotated infant gliomas, revealing 3 clinical subgroups. Group 1 tumors arise in the cerebral hemispheres and harbor alterations in the receptor tyrosine kinases ALK, ROS1, NTRK and MET. These are typically single-events and confer an intermediate outcome. Groups 2 and 3 gliomas harbor RAS/MAPK pathway mutations and arise in the hemispheres and midline, respectively. Group 2 tumors have excellent long-term survival, while group 3 tumors progress rapidly and do not respond well to chemoradiation. We conclude that infant gliomas comprise 3 subgroups, justifying the need for specialized therapeutic strategies.

Infant gliomas behave differently to their childhood or adult counterparts. Here, the authors perform a large-scale genetic analysis of these tumours, revealing genetic alterations which may offer therapeutic opportunities.

Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography

Diamond has two crystallographically inequivalent sites in the unit cell. In doped diamond, dopant occupation in the two sites is expected to be equal. Nevertheless, preferential dopant occupation during growth under nonequilibrium conditions is of fundamental importance, for example, to enhance the properties of nitrogen-vacancy (N-V) centers; therefore, this is a promising candidate for a qubit. However, the lack of suitable experimental techniques has made it difficult to study the crystal- and chemical-site-resolved local structures of dopants. Here, we confirm the identity of two chemical sites with asymmetric dopant incorporation in the diamond structure, via the photoelectron holography (PEH) of heavily phosphorus (P)-doped diamond prepared by chemical vapor deposition. One is substitutionally incorporated P with preferential site occupations and the other can be attributed to a PV split vacancy complex with preferential orientation. The present study shows that PEH is a valuable technique to study the local structures around dopants with a resolution of crystallographically inequivalent but energetically equivalent sites/orientations. Such information provides strategies to improve the properties of dopant related-complexes in which alignment is crucial for sensing of magnetic field or quantum spin register using N-V centers in diamond.

Volume effect in paediatric brain tumour resection surgery: analysis of data from the Japanese national inpatient database

BACKGROUND

Paediatric brain tumours are the second most common type of malignancies that occur during childhood. Surgical resection is usually the first step in the treatment of these patients; however, evidence pertaining to a 'volume effect' in paediatric brain tumour resection surgery and the associations among the surgical volume, clinical features and treatments are not well characterised.

METHODS

Data pertaining to paediatric patients (age ≤ 15 years) who underwent brain tumour resection surgery between April 2012 and March 2016 were retrieved from the Japanese administrative inpatient database and retrospectively analysed. Demographic characteristics, therapeutic procedures and in-hospital mortality were summarised according to the hospital surgical volume. Penalised logistic regression analysis was used to investigate the association between the hospital surgical volume and in-hospital mortality.

RESULTS

A total of 1354 paediatric patients were included. About 40% of the patients were in the 11- to 15-year age group. The male:female ratio was 53:47, the overall crude in-hospital mortality was 1.8% (n = 24) and the 30-day postoperative mortality was 0.4% (n = 6). The crude mortality ratio was 3.3% in the lowest quartile and 0.8% in the highest quartile by volume. After adjusting for covariates, a higher hospital surgical volume was associated with lower in-hospital mortality (compared with 1-4 surgeries per 4 years, 15-25 surgeries, odds ratio [OR]: 0.25; 95% confidence interval [CI]: 0.05-0.90, p = 0.033; ≥26 surgeries, OR: 0.31; 95% CI: 0.08-0.96, p = 0.042).

CONCLUSIONS

The present study indicated a volume-outcome relationship in paediatric brain tumour resection surgery cases. Further centralisation of surgeries should be considered to achieve better outcomes.

Suppression of structural instability in LaOBiS2-x Se x by Se substitution

Isovalent substitution of S by Se in LaOBiS_2-x Se _x has a substantial effect on its electronic structure and thermoelectric properties. To investigate the possible role of BiS₂ structural instability, we have studied the local structure of LaOBiS_2-x Se _x ([Formula: see text]) using temperature dependent Bi L₃-edge extended x-ray absorption fine structure measurements. The results reveal that the local structure of the two compounds is significantly different. The BiS₂ sub-lattice is largely distorted in LaOBiS₂ (x  =  0.0), with two in-plane Bi-S1 distances separated by  ∼0.4 Å instead LaOBiSSe (x  =  1.0) showing much smaller local disorder with two in-plane Bi-Se distances in the plane being separated by  ∼0.2 Å. Temperature dependent study shows that the two Bi-S1 distances are characterized by different bond strength in LaOBiS₂ (x  =  0.0) while it is similar for the Bi-Se distances in LaOBiSSe (x  =  1.0). The out of plane Bi-S2 bond is harder in LaOBiSSe indicating that the structural instability of BiS₂ layer has large effect on the out-of-plane atomic correlations. The results suggest that the local structure of LaOBiS_2-x Se _x is an important factor to describe differing electronic and thermal transport of the two compounds.

Preoperative diagnosis of clear cell sarcoma of the kidney by detection of BCOR internal tandem duplication in circulating tumor DNA

Clear cell sarcoma of the kidney (CCSK) is the second most common renal malignancy in children. The prognosis is poorer in CCSK than in Wilms' tumor, and multimodal treatment including surgery, intensive chemotherapy, and radiation is required to improve the outcome for children with CCSK. Histological evaluation is required for the diagnosis. However, biopsies of tumors to obtain diagnostic specimens are not routinely performed because of the risk of spreading tumor cells during the procedure. Recently, internal tandem duplication (ITD) of BCOR has been recognized as a genetic hallmark of CCSK. We herein established a novel BCOR-ITD-specific polymerase chain reaction method with well-designed primers, and then performed a liquid biopsy for cell-free DNA (cfDNA) obtained from plasma of three children with nonmetastatic renal tumors (stage II) and from one control. BCOR-ITD was positively detected in the cfDNA of two cases, both of which were later diagnosed as CCSK based on histological feature of the resected tumor specimen, while it was not detected for a normal control and a patient diagnosed with Wilms' tumor. Our study is the first one of preoperative circulating tumor DNA assay in pediatric renal tumors. The liquid biopsy method enables less invasive, preoperative diagnosis of CCSK with no risk of tumor spillage, which can avoid iatrogenic upstaging.