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Introduction: Regulatory decisions on paediatric investigation plans (PIPs) aim at making effective and safe medicines timely available for children with high unmet medical need. At the same time, scientific knowledge progresses continuously leading frequently to the identification of new molecular targets in the therapeutic area of oncology. This, together with further efforts to optimise next generation medicines, results in novel innovative products in development pipelines. In the context of global regulatory development requirements for these growing pipelines of innovative products (e.g. US RACE for children Act), it is an increasing challenge to complete development efforts in paediatric oncology, a therapeutic area of rare and life-threatening diseases with high unmet needs.Objective: Regulators recognise feasibility challenges of the regulatory obligations in this context. Here, we explain the EU regulatory decision making strategy applied to paediatric oncology, which aims fostering evidence generation to support developments based on needs and robust science. Because there is a plethora of products under development within given classes of or within cancer types, priorities need to be identified and updated as evidence evolves. This also includes identifying the need for third or fourth generation products to secure focused and accelerated drug development.Conclusion: An agreed PIP, as a plan, is a living document which can be modified in light of new evidence. For this to be successful, input from the various relevant stakeholders, i.e. pa-tients/parents, clinicians and investigators is required. To efficiently obtain this input, the EMA is co-organising with ACCELERATE oncology stakeholder engagement platform meet-ings.(c) 2022 Elsevier Ltd. All rights reserved.

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T-cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first- or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplantation and be definitive therapy versus those in whom it provides a more effective bridge to haematopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully humanised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prioritisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary mediastinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this population. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials. CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell therapies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success. The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies. Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regulatory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially important as these are very expensive therapies. The model for drug development for cell therapy in paediatric oncology could also involve a ‘later stage handoff’ to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies.

Background: Despite major improvements in the survival of pediatric cancer patients that were achieved through the intensification of chemotherapy and the perfection of supportive care in the past decades, treatment outcomes for high-risk, relapsed, and refractory solid cancers remain unsatisfactory. Accelerating the progress of pediatric oncology requires both therapeutic advances and attention to reducing the long-term cytotoxic treatment-related side effects. This could be achieved by targeting specific molecular changes that drive pediatric malignancies. Material and Methods: From September 2016 to August 2020, a total of 192 patients with pediatric high-risk solid tumors successfully underwent comprehensive genomic profiling. Since more than thirty patients had two or more biopsies from recurrent relapses, the total number of samples examined was 295. In the cohort, there were 78 cases of central nervous system tumors, 68 sarcomas, 14 neuroblastomas, 10 lymphomas, and 22 tumors of other histology. Whole-exome sequencing was performed in all patients, fusion gene analysis in 96% of patients, whole-transcriptome profiling in 84% of patients, and CNV analysis in 63% of patients. Results: The diagnostic yield of therapeutically actionable findings was 40%, with single-nucleotide variants and small insertions/deletions being the most common actionable alteration types. In 23% of patients, a clinically relevant gene fusion was identified. The majority of the identified fusions were of diagnostic significance, and 18% of those were therapeutically targetable gene fusions involving BRAF, RAF1, ALK, FGFR1, or NTRK2. Four patients were eligible for immunotherapy based on high tumor mutational burden (>10 mut/Mb). Lymphomas and CNS tumors showed the highest rate of patients with therapeutically actionable findings (60% and 56%, respectively), followed by neuroblastomas (36%), sarcomas (25%), and other solid tumors (23%). All results and individual treatment plans were discussed at multidisciplinary molecular tumor boards. Conclusion: Precision medicine in pediatric oncology has rapidly developed over the last decade and resulted in new therapeutic options based on molecular biomarkers and increased our understanding of the complexity of pediatric malignancies. Supported by the Ministry of Health of the Czech Republic, grant nr. NU20-03-00240 and the project National Institute for Cancer Research (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the European Union - Next Generation EU. Citation Format: Petra Pokorna, Hana Palova, Sona Adamcova, Vojtech Bystry, Michal Kyr, Dagmar Al Tukmachi, Sona Mejstrikova, Peter Mudry, Jaroslav Sterba, Ondrej Slaby. Impact of the comprehensive genomic profiling on the individual therapeutic planning in high-risk/refractory tumors: real-world precision medicine in pediatric oncology. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4511.

Vascular anomalies are a heterogeneous group of rare diseases caused by defects in the early stages of vascular development that result in abnormal growth and development of vessels. The treatment typically consists of surgical approaches; unfortunately, many anomalies cannot be cured. Therefore, the goal of the treatment is to control the lesion, and progression or recurrence after an intervention is no exception. In the last 15 years, tremendous progress in understanding the molecular basis of the disease has been made, with alterations in more than 40 genes proven to be causal in the disease pathogenesis. Interestingly, such alterations are also found in many human cancers, which recently raised the question of whether repurposing anti-cancer drugs could be utilized in this setting. Tissue biopsies from 38 patients with vascular anomalies have been analyzed using different approaches ranging from Sanger sequencing to NGS-based detection. In 31 patients, known causal alterations of either germline or somatic origin were found. For the remaining seven patients, sampling issues were considered a cause of the negative result. Given that most patients suffered from a venous type of malformation, most alterations were found in TEK and PIK3CA genes, which are commonly altered in this subgroup. Other findings included alterations of KRAS, GLMN, PTEN, or IDH2 genes. TEK gene mutations were predominantly located in exon 17, which encodes for a part of the tyrosine kinase domain of the protein, with frequent L914F substitution being found in 12 cases. Identified PIK3CA gene mutations were all well-characterized activating alterations described in cancer-related context. Based on an identification of either TEK or PIK3CA mutation, 13 patients were administered targeted treatment using selective PI3K alpha subunit inhibitor alpelisib. For all patients, improvement in quality of life, lesion reduction and normalization of coagulation parameters was achieved. A deeper understanding of the pathophysiology of vascular anomalies can significantly contribute to patient stratification, identification of potential therapeutic targets, and overall better clinical management. At the same time, identifying potential therapeutic targets could lead to the administration of novel anti-cancer drugs within the concept of drug repurposing and better overall disease control compared to routinely used approaches. Supported by the Ministry of Health of the Czech Republic, grant nr. NU20-03-00240 and by the project National Institute for Cancer Research (Programme EXCELES, ID Project No. LX22NPO5102) - Funded by the European Union - Next Generation EU. Citation Format: Petra Pokorna, Renata Faberova, Olga Koskova, Martin Sterba, Hana Palova, Katerina Kozelkova, Robin Jugas, Dagmar Al Tukmachi, Tana Machackova, Jiri Sana, Peter Mudry, Jaroslav Sterba, Ondrej Slaby. Precision medicine and cancer drug repurposing in the management of vascular anomalies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1063.

Allogeneic hematopoietic stem cell transplantation (HSCT) has become a standard part of therapy for a variety of malignant and non-malignant disorders. With improved outcomes after HSCT, increasing attention has been drawn to late complications in long-term survivors. The development of secondary malignancies is recognized as one of the most serious complications. We have evaluated data from 426 patients (272 males, 154 females) who underwent allogeneic transplantation at a median age of 7.9 years from 1989 till 2017 and were alive more than one year after transplantation for the occurrence of secondary solid tumors. We have documented the occurrence of secondary solid tumors in 20 patients (4.7%). The median duration of the development of secondary solid cancer from HSCT was 11.7 (range, 5.4-21.5 years). 18 out of 20 patients (90%) had total body irradiation (TBI) 12-14.4 Gy as a part of a conditioning regimen. All but two had transplantation for malignant disease. All patients underwent surgery and/or chemo-radiotherapy. Eighteen are alive, and two died due to the progression of their secondary malignancy. The most frequent solid cancer was thyroid carcinoma (n=9). Cumulative incidence of secondary solid cancer in all groups was 15.2±3.9%, in a group using TBI based regimen 34.7±8.9%, in non-TBI (only chemo) group was 1.5±1.1%. Overall, the cumulative incidence is statistically significantly different between the TBI based and non-TBI (chemo only) group. The incidence and number of complications following allogeneic HSCT in childhood are increasing in time. The early diagnosis of secondary malignancies is one of the key tasks of long-life multidisciplinary post-transplant care.

The objective of this study was to determine the incidence of neoplastic diseases and associated risk factors in the early stages of life.Data were retrospectively assessed in 730,000 live births between 2000 and 2019. The occurrence of tumors was monitored in the neonatal, infant (1-12 months), and toddler (13-24 months) periods. Risk factors were divided into demographic, internal, and environmental factors. The control group consisted of subjects in the same age category without oncological diseases.A total of 452 neoplastic diseases were diagnosed in the study sample. In total, 24% (110/452) manifested during the neonatal period, 45% (203/452) in infants, and 31% (139/452) at the age of 13-24 months. Any genetic disease (OR 26.68; 95% CI 7.64-93.12) and medications used by the mother (OR 3.07; 95% CI 1.32-7.15) were identified as risk factors. Without adjustment for all factors, asphyxia in the first minute, a younger age of the mother, lower pregnancy, and the presence of a congenital defect manifested themselves as risk factors.The highest risk factors for the development of early childhood tumors were identified as with medications used by the mother before or during pregnancy and genetic diseases.

Introduction Standards for chemotherapy against choroid plexus tumors (CPT) have not yet been established. Methods CPT-SIOP-2000 (NCT00500890) was an international registry for all CPT nesting a chemotherapy randomization for high-risk CPT with Carboplatin/Etoposide/Vincristine (CarbEV) versus Cyclophosphamide/Etoposide/Vincristine (CycEV). Patients older than three years were recommended to receive irradiation: focal fields for non-metastatic CPC, incompletely resected atypical choroid plexus papilloma (APP) or metastatic choroid plexus papilloma (CPP); craniospinal fields for metastatic CPC/APP and non-responsive CPC. High risk was defined as choroid plexus carcinoma (CPC), incompletely resected APP, and all metastatic CPT. From 2000 until 2010, 158 CPT patients from 23 countries were enrolled. Results For randomized CPC, the 5/10 year progression free survival (PFS) of patients on CarbEV (n = 20) were 62%/47%, respectively, compared to 27%/18%, on CycEV (n = 15), (intention-to-treat, HR 2.6, p = 0.032). Within the registry, histological grading was the most influential prognostic factor: for CPP (n = 55) the 5/10 year overall survival (OS) and the event free survival (EFS) probabilities were 100%/97% and 92%/92%, respectively; for APP (n = 49) 96%/96% and 76%/76%, respectively; and for CPC (n = 54) 65%/51% and 41%/39%, respectively. Without irradiation, 12 out of 33 patients with CPC younger than three years were alive for a median of 8.52 years. Extent of surgery and metastases were not independent prognosticators. Conclusions Chemotherapy for Choroid Plexus Carcinoma is feasible and effective. CarbEV is superior to CycEV. A subset of CPC can be cured without irradiation.

The seventh multi-stakeholder Paediatric Strategy Forum focused on chimeric antigen receptor (CAR) T-cells for children and adolescents with cancer. The development of CAR T-cells for patients with haematological malignancies, especially B-cell precursor acute lymphoblastic leukaemia (BCP-ALL), has been spectacular. However, currently, there are scientific, clinical and logistical challenges for use of CAR T-cells in BCP-ALL and other paediatric malignancies, particularly in acute myeloid leukaemia (AML), lymphomas and solid tumours. The aims of the Forum were to summarise the current landscape of CAR T-cell therapy development in paediatrics, too identify current challenges and future directions, with consideration of other immune effector modalities and ascertain the best strategies to accelerate their development and availability to children. Although the effect is of limited duration in about half of the patients, anti-CD19 CAR T cells produce high response rates in relapsed/refractory BCP-ALL and this has highlighted previously unknown mechanisms of relapse. CAR T-cell treatment as first-or second-line therapy could also potentially benefit patients whose disease has high-risk features associated with relapse and failure of conventional therapies. Identifying patients with very early and early relapse in whom CAR T-cell therapy may replace haematopoietic stem cell transplanta-tion and be definitive therapy versus those in whom it provides a more effective bridge to hae-matopoietic stem cell transplantation is a very high priority. Development of approaches to improve persistence, either by improving T cell fitness or using more humanised/fully huma-nised products and co-targeting of multiple antigens to prevent antigen escape, could potentially further optimise therapy. Many differences exist between paediatric B-cell non-Hodgkin lymphomas (B-NHL) and BCP-ALL. In view of the very small patient numbers with relapsed lymphoma, careful prior-itisation is needed to evaluate CAR T-cells in children with Burkitt lymphoma, primary medi-astinal B cell lymphoma and other NHL subtypes. Combination trials of alternative targets to CD19 (CD20 or CD22) should also be explored as a priority to improve efficacy in this pop-ulation. Development of CD30 CAR T-cell immunotherapy strategies in patients with relapsed/refractory Hodgkin lymphoma will likely be most efficiently accomplished by joint paediatric and adult trials.CAR T-cell approaches are early in development for AML and T-ALL, given the unique challenges of successful immunotherapy actualisation in these diseases. At this time, CD33 and CD123 appear to be the most universal targets in AML and CD7 in T-ALL. The results of ongoing or planned first-in-human studies are required to facilitate further understanding. There are promising early results in solid tumours, particularly with GD2 targeting cell ther-apies in neuroblastoma and central nervous system gliomas that represent significant unmet clinical needs. Further understanding of biology is critical to success.The comparative benefits of autologous versus allogeneic CAR T-cells, T-cells engineered with T cell receptors T-cells engineered with T cell receptor fusion constructs, CAR Natural Killer (NK)-cell products, bispecific T-cell engager antibodies and antibody-drug conjugates require evaluation in paediatric malignancies.Early and proactive academia and multi-company engagement are mandatory to advance cellular immunotherapies in paediatric oncology. Regulatory advice should be sought very early in the design and preparation of clinical trials of innovative medicines, for which regu-latory approval may ultimately be sought. Aligning strategic, scientific, regulatory, health technology and funding requirements from the inception of a clinical trial is especially impor-tant as these are very expensive therapies.The model for drug development for cell therapy in paediatric oncology could also involve a 'later stage handoff' to industry after early development in academic hands. Finally, and very importantly, strategies must evolve to ensure appropriate ease of access for children who need and could potentially benefit from these therapies. 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Histone 3 lysine27-to-methionine (H3-K27M) mutations most frequently occur in diffuse midline gliomas (DMGs) of the childhood pons but are also increasingly recognized in adults. Their potential heterogeneity at different ages and midline locations is vastly understudied. Here, through dissecting the single-cell transcriptomic, epigenomic and spatial architectures of a comprehensive cohort of patient H3-K27M DMGs, we delineate how age and anatomical location shape glioma cell-intrinsic and -extrinsic features in light of the shared driver mutation. We show that stem-like oligodendroglial precursor-like cells, present across all clinico-anatomical groups, display varying levels of maturation dependent on location. We reveal a previously underappreciated relationship between mesenchymal cancer cell states and age, linked to age-dependent differences in the immune microenvironment. Further, we resolve the spatial organization of H3-K27M DMG cell populations and identify a mitotic oligodendroglial-lineage niche. Collectively, our study provides a powerful framework for rational modeling and therapeutic interventions.

Histone 3 lysine27-to-methionine mutant diffuse midline gliomas (H3-K27M DMGs) are among the most lethal brain tumors. Their putative cellular hierarchy has been shown to be driven by self-renewing stem-like cells arrested in an oligodendrocyte precursor-like (OPC-like) state, of which few cells are able to differentiate towards more mature astrocyte (AC)-like and oligodendrocyte (OC)-like cells. However, the spatial organization underlying this tumor cell architecture and its microenvironmental interactions in intact H3-K27M DMG tissues remain unknown. Here, we profiled the single cell transcriptomes of 45 patient H3-K27M DMGs and derived cell population-specific marker gene combinations to characterize the single cell spatial organization of 16 tumors using targeted in situ sequencing. We thereby resolved different malignant and non-malignant cell populations including cycling, OPC-like, AC-like, OC-like, mesenchymal tumor cells, and non-malignant oligodendrocytes, astrocytes, neurons, myeloid cells, T cells, and vascular cells directly in situ. Global neighborhood analyses indicate a higher tendency of cycling OPC-like cells, vascular cells, and neurons to localize within a more restricted homogeneous compartment, whereas AC-like cells, non-malignant astrocytes and myeloid cells tend to intermingle with different cell populations in a more diffuse manner. Among malignant cells, we observed cycling OPC-like and OC-like cells to co-localize within a niche-like structure that is surrounded by more differentiated AC-like cells. We further validated this stem-like niche at the protein level using multiplexed immunofluorescence via the CODEX system. Finally, we characterized relationships between malignant and non-malignant cells, consistently identifying preferred neighborhoods of mesenchymal tumor cells with vascular and myeloid cells. Together, this study resolves the spatial architecture of H3-K27M DMG malignant and non-malignant cells at single cell resolution and identifies a local niche of the oligodendroglial lineage containing the OPC-like cancer stem-like cells, thus providing novel insights into the cancer stem-like compartment in H3-K27M DMGs and suggesting potential avenues for its perturbation.

Despite the great achievements in treating pediatric cancer patients in the last several decades, approximately one fifth of patients remains uncurable using standard therapeutic modalities and require search for innovative therapeutic approaches. Advances in sequencing techniques and bioinformatic data processing enabled identification of wide spectrum of molecular alterations including single nucleotide variants, copy number aberrations, fusion genes or changes in expression and methylation patterns, which could serve as therapeutic targets. Translation of comprehensive molecular profiling into clinical practice is still limited, however, multiple precision oncology initiatives have already explored feasibility of this approach. From September 2016 to December 2020, a total of 160 patients with high-risk solid tumors that were treated or consulted at Department of Pediatric Oncology of University Hospital Brno were subjected to molecular analysis of tumor tissue using whole-exome sequencing, targeted RNA sequencing, whole-transcriptome profiling and array-CGH. In 18 patients, 2 or more biopsies were analyzed due to relapse or progression of the disease. In the cohort, CNS tumors were the most prevalent (41%), followed by sarcomas (33%) and neuroblastoma (9%). All patients were presented at multidisciplinary molecular tumor board, where treatment recommendations were discussed. In 37% of patients (n = 59), therapeutic targets were identified. Most commonly identified targets included BRAF (n = 9), FGFR1 (n = 7), NF1 (n = 6), NRAS (n = 5) and PIK3CA (n = 4), making RAS/MAPK signaling most frequently altered pathway in the subgroup. Single nucleotide variants or small indels accounted for 65% of actionable findings, followed by fusion genes (12%), copy number aberrations (9%), CD274 expression (7%, confirmed by IHC staining for PD-L1 protein), and high tumor mutational burden (7%). Clinically relevant fusions were found in 25% of patients and 20% of identified fusions were targetable. 8 patients were eligible for immunotherapy based on either PD-L1 expression, or high tumor mutational burden (>10 mut/Mb). Using molecular-based approach in treating high-risk patients represents a promising strategy and helps to understand the complexity of pediatric malignancies though examining tumor biology at multiple levels. Implementing the concept of precision oncology into clinical practice could not only be beneficial in the context of chances for improved survival of high-risk patients, but might also be convenient for other patients, whose successful treatment comes at cost of various secondary complications due to intensive chemotherapy/radiotherapy approaches. Supported by Ministry of Health of the Czech Republic, grant nr. NV19-03-00562, NV19-03-00501, NV19-03-00559 and NU20-03-00240. All rights reserved. Citation Format: Petra Pokorna, Hana Palova, Tina Catela Ivkovic, Sona Adamcova, Michal Kyr, Vojtech Bystry, Robin Jugas, Karolina Trachtova, Dagmar Al Tukmachi, Tomas Merta, Jaroslav Juracek, Jiri Sana, Sona Mejstrikova, Marta Jezova, Peter Mudry, Zdenek Pavelka, Jaroslav Sterba, Ondrej Slaby. Comprehensive genomic profiling as an approach to guide therapeutic planning in pediatric patients with high-risk solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 76.

H3K27M-mutated diffuse midline glioma (H3K27M DMG) are an almost universally fatal disease with a median survival of less than 6 months post progression and no effective therapy. PDGFRA-signaling has shown to promote and sustain a subset of oligodendrocyte precursor-like tumor cells that are responsible for tumor propagating potential and high proliferation rates. However, first attempts to target PDGFRA in adult glioblastoma with dasatinib/imatinib or pediatric refractory brain tumors with sunitinib were not successful. We report on the first experience in two patients receiving avapritinib, a highly potent, selective, brain penetrant PDGFRA/KIT inhibitor under a compassionate use program. Our first patient with spinal H3K27M DMG developed supratentorial metastases ten months after initial diagnosis. Molecular profiling revealed de novo PDGFRA and KIT amplifications and treatment with dasatinib was initiated. Due to disease progression and novel metastases, therapy was switched to avapritinib showing near complete resolution of the previously unirradiated frontal lesion with additional disease stabilization of other metastatic sites. Following re-resection and irradiation of progressing cerebellar lesions, the patient remains clinically stable on avapritinib therapy over 12 months. The second patient with diffuse intrinsic pontine glioma showed disease progression nine months after diagnosis and was treated with focal re-irradiation (30Gy). As the tumor harbored a PDGFRA R841del alteration, avapritinib was initiated seven weeks after radiation upon further tumor progression resulting in partial response. Pharmacokinetic sampling of cerebrospinal fluid (CSF) detected an increasing CSF/plasma ratio over time and up to 4 µM avapritinib in tumor tissue. Avapritinib CSF levels in both patients were distinctly higher than dasatinib levels. Avapritinib was generally well tolerated besides lower limb edema, elevated LDH and liver enzymes. Hence, effective CNS penetration of avapritinib at pharmacologically relevant brain tumor concentrations resulted in clinical response in two patients with rapidly progressive H3K27M DMG.

Spindle cell hemangioma is a benign vascular tumor typically occurring in the dermis or subcutis of distal extremities as red–brown lesions that can grow in both size and number over time. They can be very painful and potentially disabling. A family history of cancer or previous history may be relevant and must be taken into consideration. Juxtaglomerular cell tumor (reninoma) is an extremely rare cause of secondary hypertension diagnosed mostly among adolescents and young adults. Excessive renin secretion results in secondary hyperaldosteronism. Subsequent hypokalemia and metabolic alkalosis, together with high blood pressure, are clues for clinical diagnosis. Histological examination of the excised tumor leads to a definitive diagnosis. Reninoma is found in subcapsular localization, in most cases as a solitary mass, in imaging studies of kidneys. Exceptionally, it can be located in another part of a kidney. Both spindle cell hemangioma and reninoma are extremely rare tumors in children and adolescents. Herein, the authors present a case report of a patient with hereditary BRCA1 interacting protein C-terminal helicase 1 (BRIP1) mutation, spindle cell hemangioma, and secondary hypertension caused by atypically localized reninoma.

Combining low-dose chemotherapies is a strategy for designing less toxic and more potent childhood cancer treatments. We examined the effects of combining the novel thiosemicarbazones, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), or its analog, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), with the standard chemotherapies, celecoxib (CX), etoposide (ETO), or temozolomide (TMZ). These combinations were analyzed for synergism to inhibit proliferation of three pediatric tumor cell-types, namely osteosarcoma (Saos-2), medulloblastoma (Daoy) and neuroblastoma (SH-SY5Y). In terms of mechanistic dissection, this study discovered novel thiosemicarbazone targets not previously identified and which are important for considering possible drug combinations. In this case, DpC and Dp44mT caused: (1) up-regulation of a major protein target of CX, namely cyclooxygenase-2 (COX-2), (2) down-regulation of the DNA repair protein, O6-methylguanine DNA methyltransferase (MGMT), which is known to affect TMZ resistance, (3) down-regulation of mismatch repair (MMR) proteins, MSH2 and MSH6, in Daoy and SH-SY5Y cells, and (4) down-regulation in all three cell-types of the MMR repair protein, MLH1, and also topoisomerase 2&alpha, (Topo2&alpha, ), the latter of which is an ETO target. While thiosemicarbazones up-regulate the metastasis suppressor, NDRG1, in adult cancers, it is demonstrated herein for the first time that they induce NDRG1 in all three pediatric tumor cell-types, validating its role as a potential target. In fact, siRNA studies indicated that NDRG1 was responsible for MGMT down-regulation that may prevent TMZ resistance. Examining the effects of combining thiosemicarbazones with CX, ETO, or TMZ, the most promising synergism was obtained using CX. Of interest, a positive relationship was observed between NDRG1 expression of the cell-type and the synergistic activity observed in the combination of thiosemicarbazones and CX. These studies identify novel thiosemicarbazone targets relevant to childhood cancer combination chemotherapy.

The main objective of this study was to analyze changes in the antiproliferative effect of vitamin D3, in the form of calcitriol and calcidiol, via its combined application with all-trans retinoic acid (ATRA) in osteosarcoma cell lines. The response to treatment with calcitriol and calcidiol alone was specific for each cell line. Nevertheless, we observed an enhanced effect of combined treatment with ATRA and calcitriol in the majority of the cell lines. Although the levels of respective nuclear receptors did not correlate with the sensitivity of cells to these drugs, vitamin D receptor (VDR) upregulation induced by ATRA was found in cell lines that were the most sensitive to the combined treatment. In addition, all these cell lines showed high endogenous levels of retinoic acid receptor &alpha, (RAR&alpha, ). Our study confirmed that the combination of calcitriol and ATRA can achieve enhanced antiproliferative effects in human osteosarcoma cell lines in vitro. Moreover, we provide the first evidence that ATRA is able to upregulate VDR expression in human osteosarcoma cells. According to our results, the endogenous levels of RAR&alpha, and VDR could be used as a predictor of possible synergy between ATRA and calcitriol in osteosarcoma cells.

Background The knowledge of cancer burden in the population, its time trends and the possibility of international comparison is an important starting point for cancer control programmes. Our study aimed to evaluate trends in childhood cancer epidemiology of patients aged 0–14 years in the period 1994–2016 in the Czech Republic. Methods Data on childhood cancers have been obtained from the Czech National Cancer Registry. These data were validated using the clinical database of childhood cancer patients and combined with data from death certificates. Incidence and mortality trends were assessed by the joinpoint regression method. The life tables method was used to calculate the overall age-standardised five-year survival. Results The incidence trend was stable; the age-standardised (world) cancer incidence – ASR (W) – was 173.7 per 1 million children in the period 1994–2016. However, there was apparent significant decrease in mortality: ASR (W) dropped from 58.1 per 1 million children in 1994 to 21.4 per 1 million children in 2016. The overall five-year survival increased over time by 10 %. Statistically significant improvements in survival were observed in patients with lymphoid leukaemia, astrocytomas, neuroblastomas, osteosarcomas and rhabdomyosarcomas. Conclusion Such a relevant increase in survival rates, and therefore also a decrease in mortality rates in the Czech Republic, is most likely due to improvements in diagnostic and treatment methods since the 1990s, which were facilitated by the concentration of childhood cancer patients in children’s cancer centres.

PURPOSE Children with pediatric gliomas harboring a BRAF V600E mutation have poor outcomes with current chemoradiotherapy strategies. Our aim was to study the role of targeted BRAF inhibition in these tumors. PATIENTS AND METHODS We collected clinical, imaging, molecular, and outcome information from patients with BRAF V600E–mutated glioma treated with BRAF inhibition across 29 centers from multiple countries. RESULTS Sixty-seven patients were treated with BRAF inhibition (pediatric low-grade gliomas [PLGGs], n = 56; pediatric high-grade gliomas [PHGGs], n = 11) for up to 5.6 years. Objective responses were observed in 80% of PLGGs, compared with 28% observed with conventional chemotherapy ( P < .001). These responses were rapid (median, 4 months) and sustained in 86% of tumors up to 5 years while receiving therapy. After discontinuation of BRAF inhibition, 76.5% (13 of 17) of patients with PLGG experienced rapid progression (median, 2.3 months). However, upon rechallenge with BRAF inhibition, 90% achieved an objective response. Poor prognostic factors in conventional therapies, such as concomitant homozygous deletion of CDKN2A, were not associated with lack of response to BRAF inhibition. In contrast, only 36% of those with PHGG responded to BRAF inhibition, with all but one tumor progressing within 18 months. In PLGG, responses translated to 3-year progression-free survival of 49.6% (95% CI, 35.3% to 69.5%) versus 29.8% (95% CI, 20% to 44.4%) for BRAF inhibition versus chemotherapy, respectively ( P = .02). CONCLUSION Use of BRAF inhibition results in robust and durable responses in BRAF V600E–mutated PLGG. Prospective studies are required to determine long-term survival and functional outcomes with BRAF inhibitor therapy in childhood gliomas.

The third multistakeholder Paediatric Strategy Forum organised by ACCELERATE and the European Medicines Agency focused on immune checkpoint inhibitors for use in combination therapy in children and adolescents. As immune checkpoint inhibitors, both as monotherapy and in combinations have shown impressive success in some adult malignancies and early phase trials in children of single agent checkpoint inhibitors have now been completed, it seemed an appropriate time to consider opportunities for paediatric studies of checkpoint inhibitors used in combination. Among paediatric patients, early clinical studies of checkpoint inhibitors used as monotherapy have demonstrated a high rate of activity, including complete responses, in Hodgkin lymphoma and hypermutant paediatric tumours. Activity has been very limited, however, in more common malignancies of childhood and adolescence. Furthermore, apart from tumour mutational burden, no other predictive biomarker for monotherapy activity in paediatric tumours has been identified. Based on these observations, there is collective agreement that there is no scientific rationale for children to be enrolled in new monotherapy trials of additional checkpoint inhibitors with the same mechanism of action of agents already studied (e.g. anti-PD1, anti-PDL1 anti-CTLA-4) unless additional scientific knowledge supporting a different approach becomes available. This shared perspective, based on scientific evidence and supported by paediatric oncology cooperative groups, should inform companies on whether a paediatric development plan is justified. This could then be proposed to regulators through the available regulatory tools. Generally, an academic-industry consensus on the scientific merits of a proposal before submission of a paediatric investigational plan would be of great benefit to determine which studies have the highest probability of generating new insights. There is already a rationale for the evaluation of combinations of checkpoint inhibitors with other agents in paediatric Hodgkin lymphoma and hypermutated tumours in view of the activity shown as single agents. In paediatric tumours where no single agent activity has been observed in multiple clinical trials of anti-PD1, anti-PDL1 and anti-CTLA-4 agents as monotherapy, combinations of checkpoint inhibitors with other treatment modalities should be explored when a scientific rationale indicates that they could be efficacious in paediatric cancers and not because these combinations are being evaluated in adults. Immunotherapy in the form of engineered proteins (e.g. monoclonal antibodies and T cell engaging agents) and cellular products (e.g. CAR T cells) has great therapeutic potential for benefit in paediatric cancer. The major challenge for developing checkpoint inhibitors for paediatric cancers is the lack of neoantigens (based on mutations) and corresponding antigen-specific T cells. Progress critically depends on understanding the immune macroenvironment and microenvironment and the ability of the adaptive immune system to recognise paediatric cancers in the absence of high neoantigen burden. Future clinical studies of checkpoint inhibitors in children need to build upon strong biological hypotheses that take into account the distinctive immunobiology of childhood cancers in comparison to that of checkpoint inhibitor responsive adult cancers. (C) 2020 The Authors. Published by Elsevier Ltd.

SUMMARY Over the past decade, wingless-activated (WNT) medulloblastoma has been identified as a candidate for therapy de-escalation based on excellent survival; however, a paucity of relapses has precluded additional analyses of markers of relapse. To address this gap in knowledge, an international cohort of 93 molecularly confirmed WNT MB was assembled, where 5-year progression-free survival is 0.84 (95%, 0.763–0.925) with 15 relapsed individuals identified. Maintenance chemotherapy is identified as a strong predictor of relapse, with individuals receiving high doses of cyclophosphamide or ifosphamide having only one very late molecularly confirmed relapse (p = 0.032). The anatomical location of recurrence is metastatic in 12 of 15 relapses, with 8 of 12 metastatic relapses in the lateral ventricles. Maintenance chemotherapy, specifically cumulative cyclophosphamide doses, is a significant predictor of relapse across WNT MB. Future efforts to de-escalate therapy need to carefully consider not only the radiation dose but also the chemotherapy regimen and the propensity for metastatic relapses., Graphical Abstract, In Brief Nobre et al. analyze a clinically annotated cohort of 93 WNT-activated medulloblastoma using an integrated genomic approach. A maintenance chemotherapy regimen is the strongest predictor of relapse, and cumulative cyclophosphamide doses confer a reduced risk of relapse. Unlike other medulloblastoma subgroups, WNT-activated medulloblastoma recurs most frequently in the lateral ventricles.

Serial xenotransplantation of sorted cancer cells in immunodeficient mice remains the most complex test of cancer stem cell (CSC) phenotype. However, we have demonstrated in various sarcomas that putative CSC surface markers fail to identify CSCs, thereby impeding the isolation of CSCs for subsequent analyses. Here, we utilized serial xenotransplantation of unsorted rhabdomyosarcoma cells in NOD/SCID gamma (NSG) mice as a proof-of-principle platform to investigate the molecular signature of CSCs. Indeed, serial xenotransplantation steadily enriched for rhabdomyosarcoma stem-like cells characterized by enhanced aldehyde dehydrogenase activity and increased colony and sphere formation capacity in vitro. Although the expression of core pluripotency factors (SOX2, OCT4, NANOG) and common CSC markers (CD133, ABCG2, nestin) was maintained over the passages in mice, gene expression profiling revealed gradual changes in several stemness regulators and genes linked with undifferentiated myogenic precursors, e.g., SOX4, PAX3, MIR145, and CDH15. Moreover, we identified the induction of a hybrid epithelial/mesenchymal gene expression signature that was associated with the increase in CSC number. In total, 60 genes related to epithelial or mesenchymal traits were significantly altered upon serial xenotransplantation. In silico survival analysis based on the identified potential stemness-associated genes demonstrated that serial xenotransplantation of unsorted rhabdomyosarcoma cells in NSG mice might be a useful tool for the unbiased enrichment of CSCs and the identification of novel CSC-specific targets. Using this approach, we provide evidence for a recently proposed link between the hybrid epithelial/mesenchymal phenotype and cancer stemness.

For decades, retinoids and their synthetic derivatives have been well established anticancer treatments due to their ability to regulate cell growth and induce cell differentiation and apoptosis. Many studies have reported the promising role of retinoids in attaining better outcomes for adult or pediatric patients suffering from several types of cancer, especially acute myeloid leukemia and neuroblastoma. However, even this promising differentiation therapy has some limitations: retinoid toxicity and intrinsic or acquired resistance have been observed in many patients. Therefore, the identification of molecular markers that predict the therapeutic response to retinoid treatment is undoubtedly important for retinoid use in clinical practice. The purpose of this review is to summarize the current knowledge on candidate markers, including both genetic alterations and protein markers, for retinoid resistance and sensitivity in human malignancies.