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Pediatric low-grade gliomas are the most frequent brain tumors in children. The standard approach for symptomatic unresectable tumors is chemotherapy. Recently, key molecular alterations/pathways have been identified and targeted drugs developed and tested in clinical trials. We describe our institutional experience with MAPK pathway targeted therapy. We retrospectively reviewed the medical reports of 23 patients diagnosed with PLGG and treated with either trametinib or dabrafenib at Hospital Sant Joan de Deu (Barcelona, Spain). Patients with neurofibromatosis were excluded. Objective response rate (ORR) and disease control rate (DCR) were determined using the Response Assessment in Pediatric Neuro-Oncology criteria in low-grade glioma. ORR was defined as the proportion of patients with the best overall response including complete remission (CR) or partial remission (PR). DCR was the sum of the CR, PR, and stable disease (SD) rates. ORR with trametinib was 0% (95% CI, 0%–23.2%) and DCR was 78.6% (95% CI, 49.2%–95.3%). Eleven patients had SD and three patients presented PD. ORR with dabrafenib was 41.7% (95% CI, 16.5%–71.4%), including four CR and one patient with PR. DCR with dabrafenib was 100% (95% CI, 73.5%–100%); there were seven SD and none PD. Treatment was well tolerated. Only three patients, on trametinib, presented grade 3 adverse effects: leukocytoclastic vasculitis, cheilitis, and bone infection. Our experience adds to the growing data about the efficacy and tolerability of targeted therapy in patients with PLGG. When present, toxicity is mainly mild-moderate and transient. Ongoing prospective clinical trials are trying to address if its use should be advanced to first-line therapy.

Low-grade gliomas (LGG) are the most frequent pediatric tumors associated with epilepsy. Molecular sequencing analyses have defined the genomic landscape of these tumors leading to the use of targeted therapies, which have proven to be efficacious. Ongoing clinical trials are testing the incorporation of these drugs, especially in unresectable LGG that progress after standard treatment. Nevertheless, this strategy is not extended in the field of tumor-induced epilepsy. We present a patient with drug-resistant epilepsy secondary to a BRAF V600E-mutated ganglioglioma treated with dabrafenib who showed a dramatic radiological and clinical response with marked improvement in her quality of life.

Choroid plexus tumors (CPT) can present in the baseline magnetic resonance imaging (MRI) with lesions compatible with leptomeningeal dissemination. Therapeutic strategy in this condition is controversial. We present a case of an infant with CPP and significant diffuse leptomeningeal contrast enhancement at diagnosis, which spontaneously resolved after removal of the primary tumor. In these challenging cases, several aspects, such as histopathological/molecular diagnosis and close radiological follow-up, should be taken into account to avoid unnecessary treatments.

OBJECTIVEDiffuse intrinsic pontine glioma (DIPG) is a highly aggressive and lethal brainstem tumor in children. In the 1980s, routine biopsy at presentation was abandoned since it was claimed “unnecessary” for diagnosis. In the last decade, however, several groups have reincorporated this procedure as standard of care or in the context of clinical trials. Expert neurosurgical teams report no mortality and acceptable morbidity, and no relevant complications have been previously described. The aim of this study was to review needle tract dissemination as a potential complication in DIPG.METHODSThe authors retrospectively analyzed the incidence of dissemination through surgical tracts in DIPG patients who underwent biopsy procedures at diagnosis in 3 dedicated centers. Clinical records and images as well as radiation dosimetry from diagnosis to relapse were reviewed.RESULTSFour patients (2 boys and 2 girls, age range 6–12 years) had surgical tract dissemination: in 3 cases in the needle tract and in 1 case in the Ommaya catheter tract. The median time from biopsy to identification of dissemination was 5 months (range 4–6 months). The median overall survival was 11 months (range 7–12 months). Disseminated lesions were in the marginal radiotherapy field (n = 2), out of the field (n = 1), and in the radiotherapy field (n = 1).CONCLUSIONSAlthough surgical tract dissemination in DIPG is a rare complication (associated with 2.4% of procedures in this study), it should be mentioned to patients and family when procedures involving a surgical tract are proposed. The inclusion of the needle tract in the radiotherapy field may have only limited benefit. Future studies are warranted to explore the benefit of larger radiotherapy fields in patients with DIPG.

BACKGROUND Diffuse intrinsic pontine glioma (DIPG) is a lethal condition, and therefore novel approaches are needed. Monocyte-derived dendritic cells (mDCs) pulsed with tumor antigens, as professional antigen-presenting cells, are a promising strategy for immunotherapy of invasive brain tumors. METHODS Our Ib pilot study explored the use of immunotherapy with mDCs for the treatment of newly diagnosed DIPG. Patient′s mDCs were extracted after irradiation and were primed with an allogenic tumor lysate from five patients with K27M-mutated DIPGs. The principal goal of this study was to establish the feasibility and safety of the intradermic administration of these mDC vaccines in patients with DIPG. In the absence of progression, patients received maintenance boosts of tumor lysate. Additionally, we evaluated the non-specific and antitumoral immune response generated in peripheral blood mononuclear cells (PBMC) and in cerebrospinal fluid (CSF) cells. RESULTS Nine patients were included in the study (2016–2018). Vaccines fabrication was feasible and administered in all cases without grade 3 or 4 toxicities. KLH (9/9 patients) and antitumor (8/9 patients) specific responses were identified in PBMC. Immunological responses were also confirmed in T-lymphocytes from the CSF of two patients. Twenty-four month overall survival and progression free survival was 33.3% (95 % CI 13.2% to 84.0 %) and zero, respectively. DISCUSSION These results demonstrate that mDC vaccination is feasible, safe, and generates a DIPG-specific immune response detected in PBMC and CSF. There was a trend in improved OS when compared to historic controls. This strategy shows a promising immunotherapy backbone for future combination schemas.

Histiocytoses are clonal hematopoietic disorders frequently driven by mutations mapping to the BRAF and MEK1 and MEK2 kinases. Currently, however, the developmental origins of histiocytoses in patients are not well understood, and clinically meaningful therapeutic targets outside of BRAF and MEK are undefined. In this study, we uncovered activating mutations in CSF1R and rearrangements in RET and ALK that conferred dramatic responses to selective inhibition of RET (selpercatinib) and crizotinib, respectively, in patients with histiocytosis.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm characterized by the presence of abnormal CD1a-positive (CD1a(+))/CD207(+) histiocytes. Hemophagocytic lymphohistiocytosis (HLH) represents a spectrum of hyperinflammatory syndromes typified by the dysregulated activation of the innate and adaptive immune systems. Patients with LCH, particularly those with multisystem (MS) involvement, can develop severe hyperinflammation mimicking that observed in HLH. Nevertheless, to the authors' knowledge, little is known regarding the prevalence, timing, risk factors for development, and outcomes of children and young adults who develop HLH within the context of MS-LCH (hereafter referred to LCH-associated HLH). METHODS: To gain further insights, the authors conducted a retrospective, multicenter study and collected data regarding all patients diagnosed with MS-LCH between 2000 and 2015. RESULTS: Of 384 patients with MS-LCH, 32 were reported by their primary providers to have met the diagnostic criteria for HLH, yielding an estimated 2-year cumulative incidence of 9.3% +/- 1.6%. The majority of patients developed HLH at or after the diagnosis of MS-LCH, and nearly one-third (31%) had evidence of an intercurrent infection. Patient age

BACKGROUND AND OBJECTIVE: Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive and lethal brainstem tumor in children. Dendritic cells have T-cell stimulatory capacity and, therefore, potential antitumor activity for disease control. We designed a phase Ib immunotherapy clinical trial with the use of autologous dendritic cells pulsed with an allogenic tumor cell lysate in patients with newly diagnosed DIPG after upfront irradiation (RT). METHODS: Nine patients with newly diagnosed DIPG were enrolled. Clinical and radiologic response to RT was confirmed and patients were neurologically stable and off-steroids prior to study entry. Autologous dendritic cells vaccines (ADCV) were prepared from monocytes obtained by leukapheresis. Five ADCV doses were administered intradermally during induction phase. In the absence of tumor progression, patients received 3 boosts of tumor lysate every three months. RESULTS: Non-specific and specific antitumor response was generated in 8/9 patients included in the study. Immunological responses were also confirmed in the T lymphocytes from the cerebrospinal fluid (CSF) of 2 patients. CONCLUSIONS: These preliminary results demonstrate that ADCV generates a DIPG-specific immune response detected in peripheral blood mononuclear cells and CSF. This strategy shows a promising backbone for future schemas of combination immunotherapy.

Introduction: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia characterized by the accumulation of CD1a+ CD207+ histiocytes. Hemophagocytic lymphohistiocytosis (HLH), a non-malignant histiocytic disorder, is typified by the accumulation and activation of CD8+ T cells and macrophages, which secrete high levels of pro-inflammatory cytokines. The co-existence of LCH and HLH has been reported, albeit rarely, and is believed to be associated with a poorer outcome. To better understand the relationship between these two conditions, in this study we sought to describe the incidence, risk factors for development, and outcome of HLH when it develops in children and young adults with multisystem-LCH (MS-LCH). Methods: We conducted a retrospective study involving 14 centers and collected data on 384 MS-LCH patients aged less than 30 years and who were diagnosed between year 2000 and 2015. Data collected on the eligible patients included clinical information at the time of LCH diagnosis, clinical and laboratory parameters at HLH diagnosis (for those who developed HLH), treatment and disease outcome. Patients who developed HLH were classified as having "true-HLH", which was defined as disease fulfilling 5 of 8 HLH-2004 diagnostic criteria or as "HLH-like" disorder, which was defined as fulfilling Results: Of 384 MS-LCH patients, 44 (11%) were identified with HLH (29 with true HLH and 15 with an HLH-like disorder), ranging in age from 15 days to 20.6 years (median, 1.12 years). The majority of MS-LCH patients who also had HLH were females (n=27) and had accompanying risk organ (liver, spleen and/or hematopoietic system) involvement (RO+) (n=40), as opposed to non-HLH MS-LCH patients. Among nine HLH patients tested for BRAF V600E mutation status, eight were found to be positive. Twenty (45%) patients developed HLH (true or HLH-like) concurrent (±7 days) with LCH diagnosis, while 24 (55%) developed HLH >7 days before or after LCH diagnosis. The 3-year cumulative incidence of HLH (true or HLH-like) in MS-LCH was 16.8%. The 5-year overall survival of LCH patients without HLH was 98 ± 9%, while survival for those with an HLH-like disorder or true-HLH was 75 ± 12% and 70 ± 14%, respectively (P Conclusion: The development of HLH in patients with MS-LCH was not uncommon and associated with a poorer prognosis. Young females with RO+ MS-LCH who lack bone lesions at LCH diagnosis were at increased risk of developing HLH. Ferritin levels appear to be lower in comparison to patients who develop HLH in other contexts. There are overlapping features between MS-LCH and HLH that make the clinical distinction between these disorders difficult. Accordingly, improved biomarkers are needed to facilitate the identification of HLH in patients with MS-LCH. It is anticipated that early identification of HLH and prompt intervention may improve the outcome for affected individuals. Future prospective studies are needed to better understand the underlying mechanisms and identify more effective therapies. Disclosures No relevant conflicts of interest to declare.