A Phase I and Pharmacokinetic Study of Oral Dabrafenib in Children and Adolescent Patients with Recurrent or Refractory BRAF V600 Mutation-Positive Solid Tumors

Phase II study of vemurafenib in children and young adults with tumors harboring BRAF V600 mutations: NCI-COG pediatric MATCH trial (APEC1621) Arm G

BACKGROUND

This is a phase II subprotocol of the NCI-COG Pediatric MATCH study evaluating vemurafenib, a selective oral inhibitor of BRAF V600 mutated kinase, in patients with relapsed or refractory solid tumors harboring BRAF V600 mutations.

METHODS

Patients received vemurafenib at 550 mg/m2 (maximum 960 mg/dose) orally twice daily for 28-day cycles until progression or intolerable toxicity. The primary aim was to determine the objective response rate and secondary objectives included estimating progression-free survival and assessing the tolerability of vemurafenib.

RESULTS

Twenty-two patients matched to the subprotocol and 4 patients (18%) enrolled. Primary reasons for non-enrollment were ineligibility due to exclusions of low-grade glioma (nâ=â7) and prior BRAF inhibitor therapy (nâ=â7). Enrolled diagnoses were one each of histiocytosis, ameloblastoma, Ewing sarcoma, and high-grade glioma, all with BRAF V600E mutations. Treatment was overall tolerable with mostly expected grade 1/2 adverse events (AE). Grade 3 or 4 AE on treatment were acute kidney injury, hyperglycemia, and maculopapular rash. One patient came off therapy due to AE. One patient (glioma) had an objective partial response and remained on protocol therapy for 15 cycles.

CONCLUSION

There was a low accrual rate on this MATCH subprotocol, with only 18% of those who matched with BRAFV600 mutations enrolling, resulting in early termination, and limiting study results (ClinicalTrials.gov Identifier: NCT03220035).

A critical review of RAF inhibitors in BRAF-mutated glioma treatment

BRAF gliomas have garnered significant attention in research due to the lack of effective treatments and their notable incidence, constituting 3% of all gliomas. This underlines the importance of investigating this area and the impact that targeted therapies could hold. This review discusses the development of targeted therapies for these tumors, examining the effectiveness of first-generation BRAF inhibitors such as Vemurafenib, Dabrafenib and Encorafenib, while addressing the challenges posed by paradoxical ERK activation. The advent of pan-RAF inhibitors, notably Tovorafenib, offers a promising advance, demonstrating enhanced efficacy and better penetration of the blood-brain barrier, without the issue of paradoxical activation. Nevertheless, continued research is essential to refine therapeutic strategies for BRAF-mutated gliomas, given the evolving nature of targeted therapy development.

Advances in pediatric gliomas: from molecular characterization to personalized treatments

Pediatric gliomas, consisting of both pediatric low-grade (pLGG) and high-grade gliomas (pHGG), are the most frequently occurring brain tumors in children. Over the last decade, several milestone advancements in treatments have been achieved as a result of stronger understanding of the molecular biology behind these tumors. This review provides an overview of pLGG and pHGG highlighting their clinical presentation, molecular characteristics, and latest advancements in therapeutic treatments.  Conclusion: The increasing understanding of the molecular biology characterizing pediatric low and high grade gliomas has revolutionized treatment options for these patients, especially in pLGG. The implementation of next generation sequencing techniques for these tumors is crucial in obtaining less toxic and more efficacious treatments. What is Known: • Pediatric Gliomas are the most common brain tumour in children. They are responsible for significant morbidity and mortality in this population. What is New: • Over the last two decades, there has been a significant increase in our global understanding of the molecular background of pediatric low and high grade gliomas. • The implementation of next generation sequencing techniques for these tumors is crucial in obtaining less toxic and more efficacious treatments, with the ultimate goal of improving both the survival and the quality of life of these patients.

The plasma-soluble CSF1R level is a promising prognostic indicator for pediatric Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare hematologic neoplasm characterized by the clonal proliferation of Langerhans-like cells. Colony-stimulating factor 1 receptor (CSF1R) is a membrane-bound receptor that is highly expressed in LCH cells and tumor-associated macrophages. In this study, a soluble form of CSF1R protein (sCSF1R) was identified by plasma proteome profiling, and its role in evaluating LCH prognosis was explored. We prospectively measured plasma sCSF1R levels in 104 LCH patients and 10 healthy children using ELISA. Plasma sCSF1R levels were greater in LCH patients than in healthy controls (p < .001) and significantly differed among the three disease extents, with the highest level in MS RO+ LCH patients (p < .001). Accordingly, immunofluorescence showed the highest level of membrane-bound CSF1R in MS RO+ patients. Furthermore, the plasma sCSF1R concentration at diagnosis could efficiently predict the prognosis of LCH patients treated with standard first-line treatment (AUC = 0.782, p < .001). Notably, dynamic monitoring of sCSF1R levels could predict relapse early in patients receiving BRAF inhibitor treatment. In vitro drug sensitivity data showed that sCSF1R increased resistance to Ara-C in THP-1 cells expressing ectopic BRAF-V600E. Overall, the plasma sCSF1R level at diagnosis and during follow-up is of great clinical importance in pediatric LCH patients.

Evolution of the Innovative Therapies for Children With Cancer Consortium Trial Portfolio for Drug Development for Children With Cancer

PURPOSE

The aim of the Innovative Therapies for Children with Cancer (ITCC) consortium is to improve access to novel therapies for children and adolescents with cancer. The evolution of the ITCC clinical trial portfolio since 2003 was reviewed.

METHODS

All ITCC-labeled phase I/II trials opened between January 1, 2003 and February 3, 2018 were analyzed in two periods (2003-2010 and 2011-2018), and data were extracted from the ITCC database, regulatory agencies' registries, and publications.

RESULTS

Sixty-one trials (62% industry-sponsored) enrolled 3,198 patients. The number of trials in the second period increased by almost 300% (16 v 45). All biomarker-driven trials (n = 14) were conducted in the second period. The use of rolling six and model-based designs increased (1 of 9, 11% v 21 of 31, 68%), and that of 3 + 3 designs decreased (5 of 9, 55% v 5 of 31, 16%; P = .014). The proportion of studies evaluating chemotherapeutics only decreased (5 of 16, 31% v 4 of 45, 9%), the proportion of single-agent targeted therapies did not change (9 of 16, 56.2% v 24 of 45, 53.3%), the proportion of combination targeted therapies trials increased (2 of 16, 12%, v 17 of 45, 38%), the proportion of randomized phase II trials increased (1 of 7, 14% v 8 of 14, 57%). More trials were part of a pediatric investigation plan in the second period (4 of 16, 25% v 21 of 45, 46%). The median time for Ethics Committees' approvals was 1.7 times longer for academic compared with industry-sponsored trials.

CONCLUSION

This study reports a shift in the paradigm of early drug development for childhood cancers, with more biologically relevant targets evaluated in biomarker-driven trials or in combination with other therapies and with more model-based or randomized designs and a greater focus on fulfilling regulatory requirements. Improvement of trial setup and recruitment could increase the number of patients benefiting from novel agents.

Updates on management of gliomas in the molecular age

Gliomas are primary brain tumors derived from glial cells of the central nervous system, afflicting both adults and children with distinct characteristics and therapeutic challenges. Recent developments have ushered in novel clinical and molecular prognostic factors, reshaping treatment paradigms based on classification and grading, determined by histological attributes and cellular lineage. This review article delves into the diverse treatment modalities tailored to the specific grades and molecular classifications of gliomas that are currently being discussed and used clinically in the year 2023. For adults, the therapeutic triad typically consists of surgical resection, chemotherapy, and radiotherapy. In contrast, pediatric gliomas, due to their diversity, require a more tailored approach. Although complete tumor excision can be curative based on the location and grade of the glioma, certain non-resectable cases demand a chemotherapy approach usually involving, vincristine and carboplatin. Additionally, if surgery or chemotherapy strategies are unsuccessful, Vinblastine can be used. Despite recent advancements in treatment methodologies, there remains a need of exploration in the literature, particularly concerning the efficacy of treatment regimens for isocitrate dehydrogenase type mutant astrocytomas and fine-tuned therapeutic approaches tailored for pediatric cohorts. This review article explores into the therapeutic modalities employed for both adult and pediatric gliomas in the context of their molecular classification.

Repurposing AZD5438 and Dabrafenib for Cisplatin-Induced AKI

SIGNIFICANCE STATEMENT

To combat both untoward effects of nephrotoxicity and ototoxicity in cisplatin-treated patients, two potential therapeutic oral anticancer drugs AZD5438 and dabrafenib, a phase-2 clinical trial protein kinase CDK2 inhibitor and an US Food and Drug Administration-approved drug BRAF inhibitor, respectively, were tested in an established mouse AKI model. Both drugs have previously been shown to protect significantly against cisplatin-induced hearing loss in mice. Each drug ameliorated cisplatin-induced increases in the serum biomarkers BUN, creatinine, and neutrophil gelatinase-associated lipocalin. Drugs also improved renal histopathology and inflammation, mitigated cell death by pyroptosis and necroptosis, and significantly enhanced overall survival of cisplatin-treated mice.

BACKGROUND

Cisplatin is an effective chemotherapy agent for a wide variety of solid tumors, but its use is dose-limited by serious side effects, including AKI and hearing loss. There are no US Food and Drug Administration-approved drugs to treat both side effects. Recently, two anticancer oral drugs, AZD5438 and dabrafenib, were identified as protective against cisplatin-induced hearing loss in mice. We hypothesize that similar cell stress and death pathways are activated in kidney and inner ear cells when exposed to cisplatin and tested whether these drugs alleviate cisplatin-induced AKI.

METHODS

The HK-2 cell line and adult FVB mice were used to measure the protection from cisplatin-induced cell death and AKI by these drugs. Serum markers of kidney injury, BUN, creatinine, and neutrophil gelatinase-associated lipocalin as well as histology of kidneys were analyzed. The levels of markers of kidney cell death, including necroptosis and pyroptosis, pERK, and proliferating cell nuclear antigen, were also examined by Western blotting and immunofluorescence. In addition, CDK2 knockout (KO) mice were used to confirm AZD5438 protective effect is through CDK2 inhibition.

RESULTS

The drugs reduced cisplatin-induced cell death in the HK-2 cell line and attenuated cisplatin-induced AKI in mice. The drugs reduced serum kidney injury markers, inhibited cell death, and reduced the levels of pERK and proliferating cell nuclear antigen, all of which correlated with prolonged animal survival. CDK2 KO mice were resistant to cisplatin-induced AKI, and AZD5438 conferred no additional protection in the KO mice.

CONCLUSIONS

Cisplatin-induced damage to the inner ear and kidneys shares similar cellular beneficial responses to AZD5438 and dabrafenib, highlighting the potential therapeutic use of these agents to treat both cisplatin-mediated kidney damage and hearing loss.

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.

Novel therapeutic approaches for pediatric diencephalic tumors: improving functional outcomes

Pediatric diencephalic tumors represent a histopathologically and molecularly diverse group of neoplasms arising in the central part of the brain and involving eloquent structures, including the hypothalamic-pituitary axis (HPA), optic pathway, thalamus, and pineal gland. Presenting symptoms can include significant neurological, endocrine, or visual manifestations which may be exacerbated by injudicious intervention. Upfront multidisciplinary assessment and coordinated management is crucial from the outset to ensure best short- and long-term functional outcomes. In this review we discuss the clinical and pathological features of the neoplastic entities arising in this location, and their management. We emphasize a clear move towards 'function preserving' diagnostic and therapeutic approaches with novel toxicity-sparing strategies, including targeted therapies.

A biobank of pediatric patient-derived-xenograft models in cancer precision medicine trial MAPPYACTS for relapsed and refractory tumors

Pediatric patients with recurrent and refractory cancers are in most need for new treatments. This study developed patient-derived-xenograft (PDX) models within the European MAPPYACTS cancer precision medicine trial (NCT02613962). To date, 131 PDX models were established following heterotopical and/or orthotopical implantation in immunocompromised mice: 76 sarcomas, 25 other solid tumors, 12 central nervous system tumors, 15 acute leukemias, and 3 lymphomas. PDX establishment rate was 43%. Histology, whole exome and RNA sequencing revealed a high concordance with the primary patient's tumor profile, human leukocyte-antigen characteristics and specific metabolic pathway signatures. A detailed patient molecular characterization, including specific mutations prioritized in the clinical molecular tumor boards are provided. Ninety models were shared with the IMI2 ITCC Pediatric Preclinical Proof-of-concept Platform (IMI2 ITCC-P4) for further exploitation. This PDX biobank of unique recurrent childhood cancers provides an essential support for basic and translational research and treatments development in advanced pediatric malignancies.

Unlocking the power of precision medicine for pediatric low-grade gliomas: molecular characterization for targeted therapies with enhanced safety and efficacy

In the past decade significant advancements have been made in the discovery of targetable lesions in pediatric low-grade gliomas (pLGGs). These tumors account for 30-50% of all pediatric brain tumors with generally a favorable prognosis. The latest 2021 WHO classification of pLGGs places a strong emphasis on molecular characterization for significant implications on prognosis, diagnosis, management, and the potential target treatment. With the technological advances and new applications in molecular diagnostics, the molecular characterization of pLGGs has revealed that tumors that appear similar under a microscope can have different genetic and molecular characteristics. Therefore, the new classification system divides pLGGs into several distinct subtypes based on these characteristics, enabling a more accurate strategy for diagnosis and personalized therapy based on the specific genetic and molecular abnormalities present in each tumor. This approach holds great promise for improving outcomes for patients with pLGGs, highlighting the importance of the recent breakthroughs in the discovery of targetable lesions.

Treatment of Langerhans Cell Histiocytosis and Histiocytic Disorders: A Focus on MAPK Pathway Inhibitors

Histiocytic disorders are rare diseases defined by the clonal accumulation of a macrophage or dendritic cell origin. These disorders include Langerhans cell histiocytosis, Erdheim-Chester disease, juvenile xanthogranuloma, malignant histiocytoses, and Rosai-Dorfman-Destombes disease. These histiocytic disorders are a diverse group of disorders with different presentations, management, and prognosis. This review focuses on these histiocytic disorders and the role of pathological ERK signaling due to somatic mutations in the mitogen--activated protein kinase (MAPK) pathway. Over the last decade, there has been growing awareness of the MAPK pathway being a key driver in many histiocytic disorders, which has led to successful treatment with targeted therapies, in particular, BRAF inhibitors and MEK inhibitors.

Clinical outcomes and prognostic risk factors of Langerhans cell histiocytosis in children: Results from the BCH-LCH 2014 protocol study

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm mainly affecting young children. This study aimed to evaluate the outcomes of 449 pediatric patients enrolled in the BCH-LCH 2014 study. 52.6% of patients were classified with single-system (SS) LCH, 28.1% with multisystem (MS) risk organ negative (RO-) LCH, and 19.4% with MS RO+ LCH. Three hundred ninety-six patients (88.2%) were initially treated with first-line therapy based on the vindesine-prednisone combination. One hundred thirty-nine patients who lacked a response to initial treatment were shifted to second-line therapy, 72 to intensive treatment Arm S1 (a combination of cytarabine, cladribine, vindesine, and dexamethasone), and 67 to Arm S2 (without cladribine). The 5-year overall survival (OS), progression-free survival (PFS), and relapse rates were 98.2% (median: 97.6 months), 54.6% (median: 58.3 months), and 29.9%, respectively. MS RO+ patients had the worst prognosis among the three clinical subtypes. For the patients initially treated with first-line therapy, the 5-year OS, PFS, and relapse rates were 99.2%, 54.5%, and 29.3%, respectively. Patients in Arm S1 had a significantly better prognosis than patients in Arm S2 (5-year PFS: 69.2% vs. 46.5%, p = .042; relapse rate: 23.4% vs. 44.2%, p = .031). Multivariate analysis revealed that early treatment response, the involvement of RO, skin, and oral mucosa, as well as laboratory parameters, including CRP and γ-GT, were independent risk factors for the PFS of LCH. Thus, the prognosis of LCH in children has been improved significantly with stratified chemotherapy, and progression and relapse remained the challenges, especially for RO+ patients.

Development of Novel Murine BRAFV600E-Driven Papillary Thyroid Cancer Cell Lines for Modeling of Disease Progression and Preclinical Evaluation of Therapeutics

The Cancer Genome Atlas study in thyroid cancer exposed the genomic landscape of ~500 PTCs and revealed BRAFV600E-mutant tumors as having different prognosis, contrasting indolent cases and those with more invasive disease. Here, we describe the generation and characterization of six novel BRAFV600E-driven papillary thyroid cancer (PTC) cell lines established from a BrafV600E+/-/Pten+/-/TPO-Cre mouse model that spontaneously develop thyroid tumors. The novel cell lines were obtained from animals representing a range of developmental stages and both sexes, with the goal of establishing a heterogeneous panel of PTC cell lines sharing a common driver mutation. These cell lines recapitulate the genetics and diverse histopathological features of BRAFV600E-driven PTC, exhibiting differing degrees of growth, differentiation, and invasive potential that may help define mechanisms of pathogenesis underlying the heterogeneity present in the patient population. We demonstrate that these cell lines can be used for a variety of in vitro applications and can maintain the potential for in vivo transplantation into immunocompetent hosts. We believe that these novel cell lines will provide powerful tools for investigating the molecular basis of thyroid cancer progression and will lead to the development of more personalized diagnostic and treatment strategies for BRAFV600E-driven PTC.

Efficacy and Safety of Trametinib Monotherapy or in Combination With Dabrafenib in Pediatric BRAF V600-Mutant Low-Grade Glioma

PURPOSE

BRAF V600 mutations occur in many childhood cancers, including approximately 20% of low-grade gliomas (LGGs). Here, we describe a phase I/II study establishing pediatric dosing and pharmacokinetics of trametinib with or without dabrafenib, as well as efficacy and safety in a disease-specific cohort with BRAF V600-mutant LGG; other cohorts will be reported elsewhere.

METHODS

This is a four-part, phase I/II study (ClinicalTrials.gov identifier: NCT02124772) in patients age < 18 years with relapsed/refractory malignancies: trametinib monotherapy dose finding (part A) and disease-specific expansion (part B), and dabrafenib + trametinib dose finding (part C) and disease-specific expansion (part D). The primary objective assessed in all patients in parts A and C was to determine pediatric dosing on the basis of steady-state pharmacokinetics. Disease-specific efficacy and safety (across parts A-D) were secondary objectives.

RESULTS

Overall, 139 patients received trametinib (n = 91) or dabrafenib + trametinib (n = 48). Trametinib dose-limiting toxicities in > 1 patient (part A) included mucosal inflammation (n = 3) and hyponatremia (n = 2). There were no dose-limiting toxicities with combination therapy (part C). The recommended phase II dose of trametinib, with or without dabrafenib, was 0.032 mg/kg once daily for patients age < 6 years and 0.025 mg/kg once daily for patients age ≥ 6 years; dabrafenib dosing in the combination was as previously identified for monotherapy. In 49 patients with BRAF V600-mutant glioma (LGG, n = 47) across all four study parts, independently assessed objective response rates were 15% (95% CI, 1.9 to 45.4) for monotherapy (n = 13) and 25% (95% CI, 12.1 to 42.2) for combination (n = 36). Adverse event-related treatment discontinuations were more common with monotherapy (54% v 22%).

CONCLUSION

The trial design provided efficient evaluation of pediatric dosing, safety, and efficacy of single-agent and combination targeted therapy. Age-based and weight-based dosing of trametinib with or without dabrafenib achieved target concentrations with manageable safety and demonstrated clinical efficacy and tolerability in BRAF V600-mutant LGG.

BRAF-mediated brain tumors in adults and children: A review and the Australian and New Zealand experience

The mitogen-activated protein kinase (MAPK) pathway signaling pathway is one of the most commonly mutated pathways in human cancers. In particular, BRAF alterations result in constitutive activation of the rapidly accelerating fibrosarcoma-extracellular signal-regulated kinase-MAPK significant pathway, leading to cellular proliferation, survival, and dedifferentiation. The role of BRAF mutations in oncogenesis and tumorigenesis has spurred the development of targeted agents, which have been successful in treating many adult cancers. Despite advances in other cancer types, the morbidity and survival outcomes of patients with glioma have remained relatively stagnant. Recently, there has been recognition that MAPK dysregulation is almost universally present in paediatric and adult gliomas. These findings, accompanying broad molecular characterization of gliomas, has aided prognostication and offered opportunities for clinical trials testing targeted agents. The use of targeted therapies in this disease represents a paradigm shift, although the biochemical complexities has resulted in unexpected challenges in the development of effective BRAF inhibitors. Despite these challenges, there are promising data to support the use of BRAF inhibitors alone and in combination with MEK inhibitors for patients with both low-grade and high-grade glioma across age groups. Safety and efficacy data demonstrate that many of the toxicities of these targeted agents are tolerable while offering objective responses. Newer clinical trials will examine the use of these therapies in the upfront setting. Appropriate duration of therapy and durability of response remains unclear in the glioma patient cohort. Longitudinal efficacy and toxicity data are needed. Furthermore, access to these medications remains challenging outside of clinical trials in Australia and New Zealand. Compassionate access is limited, and advocacy for mechanism of action-based drug approval is ongoing.

Integrated response analysis of pediatric low-grade gliomas during and after targeted therapy treatment

Background

Pediatric low-grade gliomas (pLGGs) are the most common central nervous system tumor in children, characterized by RAS/MAPK pathway driver alterations. Genomic advances have facilitated the use of molecular targeted therapies, however, their long-term impact on tumor behavior remains critically unanswered.

Methods

We performed an IRB-approved, retrospective chart and imaging review of pLGGs treated with off-label targeted therapy at Dana-Farber/Boston Children's from 2010 to 2020. Response analysis was performed for BRAFV600E and BRAF fusion/duplication-driven pLGG subsets.

Results

Fifty-five patients were identified (dabrafenib n = 15, everolimus n = 26, trametinib n = 11, and vemurafenib n = 3). Median duration of targeted therapy was 9.48 months (0.12-58.44). The 1-year, 3-year, and 5-year EFS from targeted therapy initiation were 62.1%, 38.2%, and 31.8%, respectively. Mean volumetric change for BRAFV600E mutated pLGG on BRAF inhibitors was -54.11%; median time to best volumetric response was 8.28 months with 9 of 12 (75%) objective RAPNO responses. Median time to largest volume post-treatment was 2.86 months (+13.49%); mean volume by the last follow-up was -14.02%. Mean volumetric change for BRAF fusion/duplication pLGG on trametinib was +7.34%; median time to best volumetric response was 6.71 months with 3 of 7 (43%) objective RAPNO responses. Median time to largest volume post-treatment was 2.38 months (+71.86%); mean volume by the last follow-up was +39.41%.

Conclusions

Our integrated analysis suggests variability in response by pLGG molecular subgroup and targeted therapy, as well as the transience of some tumor growth following targeted therapy cessation.

Pediatric low-grade glioma: Targeted therapeutics and clinical trials in the molecular era

pLGGs are a group of tumors for which the era of molecular diagnostics has truly shifted treatment paradigms and patient care. The discovery that this group of tumors is driven by single-gene alterations/fusions in the MAPK pathway has resulted in relatively rapid translation into targeted therapy options for patients with this often chronic disease. This translation has been facilitated through efforts of multiple collaboratives and consortia and has led to the development of clinical trials testing the role of targeted therapies in pLGG. Although these developments represent promise, many questions remain regarding these therapies including their long-term toxicities and their potential effects on the natural history of pLGG.

Practical Recommendations for the Manipulation of Kinase Inhibitor Formulations to Age-Appropriate Dosage Forms

Over 75 kinase inhibitors (KIs) have been approved for the treatment of various cancers. KIs are orally administrated but mostly lack pediatric age-appropriate dosage forms or instructions for dose manipulation. This is highly problematic for clinical practice in pediatric oncology, as flexible oral formulations are essential to individually set dosages and to adjust it to a child's swallowability. Most KIs are poorly soluble, categorized in Biopharmaceutics Classification System (BCS) class II or IV, and improperly manipulating the KI formulation can alter pharmacokinetics and jeopardize KI drug safety and efficacy. Therefore, the goals of this review were to provide practical recommendations for manipulating the formulation of the 15 most frequently used KIs in pediatric oncology (i.e., bosutinib, cabozantinib, cobimetinib, crizotinib, dabrafenib, dasatinib, entrectinib, imatinib, larotrectinib, nilotinib, ponatinib, ruxolitinib, selumetinib, sunitinib and trametinib) based on available literature studies and fundamental drug characteristics and to establish a decision tool that supports decisions regarding formulation manipulation of solid oral dosages of KIs that have been or will be licensed (for adult and/or pediatric cancers) but are not included in this review.

Paediatric Strategy Forum for medicinal product development in mitogen-activated protein kinase pathway inhibitors: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

As the mitogen-activated protein kinase (MAPK) signalling pathway is activated in many paediatric cancers, it is an important therapeutic target. Currently, a range of targeted MAPK pathway inhibitors are being developed in adults. However, MAPK signals through many cascades and feedback loops and perturbing the MAPK pathway may have substantial influence on other pathways as well as normal development. In view of these issues, the ninth Paediatric Strategy Forum focused on MAPK inhibitors. Development of MAPK pathway inhibitors to date has been predominantly driven by adult indications such as malignant melanoma. However, these inhibitors may also target unmet needs in paediatric low-grade gliomas, high-grade gliomas, Langerhans cell histiocytosis, juvenile myelomonocytic leukaemia and several other paediatric conditions. Although MAPK inhibitors have demonstrated activity in paediatric cancer, the response rates and duration of responses needs improvement and better documentation. The rapid development and evaluation of combination approaches, based on a deep understanding of biology, is required to optimise responses and to avoid paradoxical tumour growth and other unintended consequences including severe toxicity. Better inhibitors with higher central nervous systempenetration for primary brain tumours and cancers with a propensity for central nervous system metastases need to be studied to determine if they are more effective than agents currently being used, and the optimum duration of therapy with MAPK inhibition needs to be determined. Systematic and coordinated clinical investigations to inform future treatment strategies with MAPK inhibitors, rather than use outside of clinical trials, are needed to fully assess the risks and benefits of these single agents and combination strategies in both front-line and in the refractory/relapse settings. Platform trials could address the investigation of multiple similar products and combinations. Accelerating the introduction of MAPK inhibitors into front-line paediatric studies is a priority, as is ensuring that these studies generate data appropriate for scientific and regulatory purposes. Early discussions with regulators are crucial, particularly if external controls are considered as randomised control trials in small patient populations can be challenging. Functional end-points specific to the populations in which they are studied, such as visual acuity, motor and neuro psychological function are important, as these outcomes are often more reflective of benefit for lower grade tumours (such as paediatric low-grade glioma and plexiform neurofibroma) and should be included in initial study designs for paediatric low-grade glioma. Early prospective discussions and agreements with regulators are necessary. Long-term follow-up of patients receiving MAPK inhibitors is crucial in view of their prolonged administration and the important involvement of this pathway in normal development. Further rational development, with a detailed understanding of biology of this class of products, is crucial to ensure they provide optimal benefit while minimising toxicity to children and adolescents with cancer.

Early experience with targeted therapy as a first-line adjuvant treatment for pediatric low-grade glioma

OBJECTIVE

Pediatric low-grade gliomas (pLGGs) frequently exhibit dysregulation of the mitogen-activated protein kinase (MAPK) pathway. Targeted therapies, including mutant BRAF inhibitors (dabrafenib) and MEK inhibitors (trametinib), have shown promise in patients in whom conventional chemotherapy has failed. However, few studies have investigated the use of targeted therapy as a first-line treatment for pLGG. Here, the authors reviewed their institutional experience with using a personalized medicine approach to patients with newly diagnosed pLGGs.

METHODS

All pediatric patients at the authors' institution who had been treated with dabrafenib or trametinib for pLGG without first receiving conventional chemotherapy or radiation were retrospectively reviewed. Demographic, clinical, and radiological data were collected.

RESULTS

Eight patients underwent targeted therapy as a first-line treatment for pLGG. Five patients had a BRAF alteration (1 with a BRAFV600E mutation, 4 with a KIAA1549:BRAF fusion), and 3 patients had an NF1 mutation. One of the 8 patients was initially treated with dabrafenib, and trametinib was added later. Seven patients were initially treated with trametinib; of these, 2 later transitioned to dual therapy, whereas 5 continued with trametinib monotherapy. Six patients (75%) demonstrated a partial response to therapy during their treatment course, whereas stable disease was identified in the remaining 2 patients (25%). One patient experienced mild disease progression after completing a course of trametinib monotherapy, but ultimately stabilized after a period of close observation. Another patient experienced tumor progression while on dabrafenib, but subsequently responded to dual therapy with dabrafenib and trametinib. The most common adverse reactions to targeted therapy were cutaneous toxicity (100%) and diarrhea (50%).

CONCLUSIONS

Targeted therapies have the potential to become a standard treatment option for pLGG due to their favorable toxicity profile and oral route of administration. This case series provides preliminary evidence that targeted therapies can induce an early disease response as a first-line adjuvant treatment; however, large-scale studies are required to assess long-term durability and safety.

Medical Treatment of Pediatric Low-Grade Glioma

Low-grade glioma (LGG) is the most common brain tumor in children and has excellent long-term survival. With an excellent survival rate, the choice of treatment involves careful consideration of minimizing late toxicity from surgery, radiation, and chemotherapy. Surgery, radiation therapy, and chemotherapy can be used as monotherapy or in combination, providing different therapeutic ratios and complications. As a result, establishing the selection of ideal therapies has been a controversial area, presenting challenges. Recent advances in understanding molecular characteristics of pediatric LGG affect classification and treatment approaches. This review aims to overview recent developments in medical treatment in pediatric LGG.

Prognostic factors in diffuse leptomeningeal glioneuronal tumor (DLGNT): a systematic review

BACKGROUND

Diffuse leptomeningeal glioneuronal tumor (DLGNT) is a rare tumor, first described by the WHO Classification of Central Nervous System Tumors in 2016. The clinical course is variable. Most tumors have low-grade histological findings although some may have more aggressive features. The goal of this systematic review was to identify prognostic factors for poor overall survival (OS).

MATERIAL AND METHODS

We performed a systematic review using three databases (PubMed, Google Scholar, and Embase) and the following search terms: diffuse leptomeningeal glioneuronal tumor, DLGNT, DLMGNT. Statistical analysis was performed using Statistica 13.3.

RESULTS

We included 34 reports in our review comprising 63 patients, published from 2016 to 2022. The median OS was 19 months (range: 12-51 months). Using multivariable Cox survival analysis, we showed that Ki-67 ≥ 7%, age > 9 years, symptoms of elevated intracranial pressure (ICP) at admission, and the presence of contrast-enhancing intraparenchymal tumor are associated with poor OS. Receiver operating characteristic (ROC) analysis identified Ki-67 ≥ 7% as a significant predictor of poor OS.

CONCLUSIONS

Signs or symptoms of increased ICP with imaging findings of diffuse leptomeningeal enhancement should raise suspicion for DLGNT. In our systematic review, Ki-67 ≥ 7% was the most important prognostic factor for OS in DLGNT. The presence of intraparenchymal tumor with contrast enhancement was thought to represent disease progression and, together with patient age, was associated with poor OS.

Retrospective and integrative analyses of molecular characteristics and their specific imaging parameters in pediatric grade 1 gliomas

BACKGROUND

Pediatric low-grade gliomas (PLGG) are the most common brain tumors diagnosed during childhood and represent a heterogeneous group associating variable molecular abnormalities. To go further and develop specific statistical patterns between tumor molecular background, imaging features, and patient outcome, a retrospective study was performed in a group of non-neurofibromatosis type 1 (non-NF1) grade 1 PLGGs.

PATIENTS AND METHODS

Seventy-eight children, followed from 2004 to 2017, were retrospectively reported. In this population, we analyzed radiological and molecular parameters. Their therapeutic management comprised surgery or surgery plus chemotherapies.

RESULTS

Considering all 78 patients, 59 had only a surgical removal and 19 patients were treated with postoperative chemotherapy. Twelve progressions were reported in the partially resected and chemotherapeutic groups, whereas four deaths occurred only in the highly treated patients. As expected, in the global cohort, PLGG with BRAF p.V600E and/or CDKN2A loss exhibited poor outcomes and we evidenced significant associations between those molecular characteristics and their imaging presentation. In the chemo-treated patients, when associating initial and 6-month magnetic resonance imaging (MRI) parameters to the molecular features, the good risk situations were significantly linked to the presence of a large tumor cyst at diagnosis and the appearance during treatment of a higher cystic proportion that we called cystic conversion.

CONCLUSION

So, additionally to the presence of BRAF p.V600E or CDKN2A deletion in grade 1 PLGGs, the absence on diagnostic MRI of cystic parts and/or cystic conversion at 6-month chemotherapy were significantly linked to a worst prognosis and response to treatment. These imaging features should be considered as prognostic markers in future PLGG studies.

Novel Pharmacological Treatment Options in Pediatric Glioblastoma-A Systematic Review

Simple Summary

Childhood glioblastoma is an aggressive brain tumor in children that has a very poor prognosis. Standard therapy includes surgery, irradiation and chemotherapy with temozolomide. So far, there is no effective drug treatment for pediatric glioblastoma patients. This systematic review aims to outline currently available data on novel pharmacological treatment options. None of the included phase II studies showed any benefit regarding overall survival or a prolongation of stable disease. New genomic technologies discovered the biologic heterogeneity of these tumors, demanding more individualized immunotherapeutic and targeted approaches. Autoimmune modulated therapies and further targeting of tumor-specific receptors provide promising preclinical results. Clinical trials aligned to the tumor characteristics are needed to establish effective new therapeutic approaches.

Abstract

Background: Pediatric glioblastoma (GBM) is an aggressive central nervous system tumor in children that has dismal prognosis. Standard of care is surgery with subsequent irradiation and temozolomide. We aimed to outline currently available data on novel pharmacological treatments for pediatric GBM. Methods: We conducted a systematic literature search in PubMed and Embase, including reports published in English from 2010 to 2021. We included randomized trials, cohort studies and case series. Phase I trials were not analyzed. We followed PRISMA guidelines, assessed the quality of the eligible reports using the Newcastle-Ottawa scale (NOS) and the RoB-2 tool and registered the protocol on PROSPERO. Results: We included 6 out of 1122 screened reports. All six selected reports were prospective, multicenter phase II trials (five single-arm and one randomized controlled trial). None of the investigated novel treatment modalities showed any benefit regarding overall or progression free survival. Conclusions: To date, the role of pharmacological approaches regarding pediatric GBM remains unclear, since no novel treatment approach could provide a significant impact on overall or progression free survival. Further research should aim to combine different treatment strategies in large international multicenter trials with central comprehensive diagnostics regarding subgrouping. These novel treatment approaches should include targeted and immunotherapeutic treatments, potentially leading to a more successful outcome.

Tissue-Agnostic Activity of BRAF plus MEK Inhibitor in BRAF V600-Mutant Tumors

BRAF plus MEK inhibitor combinations are currently FDA-approved for melanoma, non-small cell lung cancer, and anaplastic thyroid cancer. The lack of clinical benefit with BRAF inhibition in BRAF V600-mutated colorectal cancer has prevented its tissue-agnostic drug development. We reviewed the AACR GENIE database for the prevalence of BRAF V600 mutations across tumor types. We reviewed the literature for case reports of clinical responses, outcomes in patients with BRAF V600 mutation-positive nonmelanoma malignancies who received BRAF inhibitor therapy, and data from published adult and pediatric trials. BRAF V600 mutations are prevalent across multiple nonmelanoma malignancies (>40 different tumor types), lead to oncogene addiction, and are clinically actionable in a broad range of adult and pediatric nonmelanoma rare malignancies. Continued tissue-agnostic drug development is warranted beyond the current BRAF plus MEK approved cancers.

Upfront Molecular Targeted Therapy for the Treatment of BRAF-Mutant Pediatric High-Grade Glioma

BACKGROUND

The prognosis for patients with pediatric high-grade glioma (pHGG) is poor despite aggressive multi-modal therapy. Objective responses to targeted therapy with BRAF inhibitors have been reported in some patients with recurrent BRAF-mutant pHGG but are rarely sustained.

METHODS

We performed a retrospective, multi-institutional review of patients with BRAF-mutant pHGG treated with off-label BRAF +/- MEK inhibitors as part of their initial therapy.

RESULTS

Nineteen patients were identified, with a median age of 11.7 years (range, 2.3-21.4). Histologic diagnoses included HGG (n=6), glioblastoma (n=3), anaplastic ganglioglioma (n=4), diffuse midline glioma (n=3), high-grade neuroepithelial tumor (n=1), anaplastic astrocytoma (n=1), and anaplastic astroblastoma (n=1). Recurrent concomitant oncogenic alterations included CDKN2A/B loss, H3 K27M, as well as mutations in ATRX, EGFR and TERT. Eight patients received BRAF inhibitor monotherapy. Eleven patients received combination therapy with BRAF and MEK inhibitors. Most patients tolerated long-term treatment well with no grade 4-5 toxicities. Objective and durable imaging responses were seen in the majority of patients with measurable disease. At a median follow-up of 2.3 years (range, 0.3-6.5), three-year progression-free and overall survival for the cohort were 65% and 82%, respectively, and superior to a historical control cohort of BRAF-mutant pHGG patients treated with conventional therapies.

CONCLUSIONS

Upfront targeted therapy for patients with BRAF-mutant pHGG is feasible and effective, with superior clinical outcomes compared to historical data. This promising treatment paradigm is currently being evaluated prospectively in the Children's Oncology Group ACNS1723 clinical trial.

Clinical features and treatment outcomes of pediatric Langerhans cell histiocytosis with macrophage activation syndrome-hemophagocytic lymphohistiocytosis

Background

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm. A few LCH patients had Macrophage activation syndrome-hemophagocytic lymphohistiocytosis (MAS-HLH), a life-threatening, hyper-inflammatory syndrome. We retrospectively described the clinical-biological characteristics of a series of 28 pediatric LCH patients with MAS-HLH in a single center. We further analyzed the difference in treatment outcomes between second-line chemotherapy (cytarabine and cladribine) and targeted therapy (dabrafenib) for BRAF-V600E-positive patients.

Results

LCH patients with MAS-HLH were aged < 2 years, harbored high frequencies of risk organ, skin, or lymph nodes involvement, and most of them carried BRAF-V600E mutation in lesions (88.0%) or plasma (90.5%). Patients were firstly treated with the initial induction first-line therapy (vindesine-steroid combination), and most of them (26/28) failed to control the active MAS-HLH after one six-week course of induction treatment. Then they were shifted to second-line chemotherapy or targeted therapy dabrafenib. BRAF-V600E-mutant patients treated with dabrafenib had prompt resolution of MAS-HLH signs and symptoms with less toxicity than second-line chemotherapy. Moreover, the progression-free survival (PFS) rate for patients given dabrafenib was much higher than those treated with chemotherapy (4 year-PFS: 75% vs. 14.6%, P = 0.034).

Conclusions

LCH patients with MAS-HLH harbored specific clinical-biology characteristics compared to the multisystem LCH without MAS-HLH. The BRAF inhibitor dabrafenib provides a promising treatment option for LCH with MAS-HLH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02276-y.

DIPG Harbors Alterations Targetable by MEK Inhibitors, with Acquired Resistance Mechanisms Overcome by Combinatorial Inhibition

The survival of children with diffuse intrinsic pontine glioma (DIPG) remains dismal, with new treatments desperately needed. In a prospective biopsy-stratified clinical trial, we combined detailed molecular profiling and drug screening in newly established patient-derived models in vitro and in vivo. We identified in vitro sensitivity to MEK inhibitors in DIPGs harboring MAPK pathway alterations, but treatment of patient-derived xenograft models and a patient at relapse failed to elicit a significant response. We generated trametinib-resistant clones in a BRAFG469V model through continuous drug exposure and identified acquired mutations in MEK1/2 with sustained pathway upregulation. These cells showed hallmarks of mesenchymal transition and expression signatures overlapping with inherently trametinib-insensitive patient-derived cells, predicting sensitivity to dasatinib. Combined trametinib and dasatinib showed highly synergistic effects in vitro and on ex vivo brain slices. We highlight the MAPK pathway as a therapeutic target in DIPG and show the importance of parallel resistance modeling and combinatorial treatments for meaningful clinical translation.

SIGNIFICANCE

We report alterations in the MAPK pathway in DIPGs to confer initial sensitivity to targeted MEK inhibition. We further identify for the first time the mechanism of resistance to single-agent targeted therapy in these tumors and suggest a novel combinatorial treatment strategy to overcome it in the clinic. This article is highlighted in the In This Issue feature, p. 587.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

Liver transplantation in a child with liver cirrhosis caused by langerhans cell histiocytosis: a case report

Background

Langerhans cell histiocytosis (LCH) is a rare condition that has a variety of clinical manifestations. But LCH in children localized only in the hepatobiliary system is unusual.

Case presentation.

Here we reported a rare case of a 2-year-old boy who was serendipitously found to have elevated liver enzymes while undergoing treatment of a perianal abscess. After a period of earlier conservative treatment in another hospital, the perianal abscess had resolved but the levels of liver enzymes were still rising slowly. The child was then referred to our institution for a definitive diagnosis. After laboratory tests, imaging and pathological examinations, a diagnosis of liver cirrhosis and sclerosing cholangitis was established, although the cause was unclear. Subsequently, living-donor liver transplantation was performed due to deterioration in liver function. Following successful liver transplantation, a diagnosis of LCH localized only within the hepatobiliary system was finally confirmed, based on additional pathological and imaging investigation. Additionally, the BRAF V600E mutation in this patient was also confirmed. The child has now recovered without evidence of LCH recurrence.

Conclusions

LCH localized only within the hepatobiliary system is unusual. The presence of unexplainable sclerosing cholangitis and liver cirrhosis in any child should raise the suspicion of LCH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-03090-4.

Dermatologic toxicities of targeted antineoplastic agents and immune checkpoint inhibitor therapy in pediatric patients: A systematic review

Cutaneous adverse events (cAEs) from targeted antineoplastic agents and immune checkpoint inhibitors are common in children with cancer and may lead to dose reduction or cessation of critical oncologic treatment. Timely diagnosis and proper management of cAEs in pediatric oncology patients is essential to optimize ongoing cancer-directed therapy and improve quality of life. This systematic review of published studies summarizes dermatologic toxicities to targeted anticancer treatments and immune checkpoint inhibitors.

Development and Validation of a Five-RNA-Based Signature and Identification of Candidate Drugs for Neuroblastoma

Neuroblastoma (NBL) originating from the sympathetic nervous system is the most prevalent solid tumor in infancy. Although there is sufficient variability in prognosis among different age pyramids, age-related gene expression profiles and biomarkers remain poorly explored. The present study aimed to construct a signature based on differentially expressed genes (DEGs) between two age groups in NBL. Univariate Cox regression, multivariate Cox regression, and LASSO analyses were used to identify the optimal prognostic factors. The prediction ability of the model was assessed using the receiver operating characteristic (ROC) curve and C-index. Functional enrichment analysis was performed using the Kyoto Encyclopedia of Genes and Genomes and gene ontology databases. A total of 1,160 DEGs were identified between the two groups, and 204 DEGs impacted the survival of NBL. Functional enrichment analysis revealed that the DEGs were involved in retinol metabolism, cholesterol metabolism, and glycolysis/gluconeogenesis pathways. Five RNAs, namely F8A3, PDF, ANKRD24, FAXDC2, and TMEM160 were recruited into the signature. They were correlated with COG risk classification, INSS stage, and histology. MYCN amplification was linked to FAXDC2, TMEM160, PDF, and F8A3. The expression levels of ANKRD24, PDF, and TMEM160 were lower in the hyperdiploid groups. Only FAXDC2 levels were different in the different MKI grades. The ROC curve showed that the five-RNA–based signatures effectively predicted the OS of NBL (3-years AUC = 0.791, 5-years AUC = 0.816) in the TARGET cohort. The predictive capability was also validated by the GSE49711 cohort (3-years AUC = 0.851, 5-years AUC = 0.848). The C-index in the TARGET and GSE49711 cohorts was 0.749 and 0.809, respectively. The potential mechanisms of the five RNAs were also explored via gene set enrichment analysis, and candidate drugs targeting the five genes, including dabrafenib, vemurafenib, and bafetinib, were screened. In conclusion, we constructed a five-RNA–based signature to predict the survival of NBL and screened candidate agents against NBL.

BRAF Signaling Inhibition in Glioblastoma: Which Clinical Perspectives?

IDH-wild type (wt) glioblastoma (GB) accounts for approximately 90% of all GB and has a poor outcome. Surgery and adjuvant therapy with temozolomide and radiotherapy is the main therapeutic approach. Unfortunately, after relapse and progression, which occurs in most cases, there are very limited therapeutic options available. BRAF which plays a role in the oncogenesis of several malignant tumors, is also involved in a small proportion of IDH-wt GB. Previous successes with anti-B-Raf targeted therapy in tumors with V600E BRAF mutation like melanoma, combined with the poor prognosis and paucity of therapeutic options for GB patients is leading to a growing interest in the potential efficacy of this approach. This review is thus focused on dissecting the state of the art and future perspectives on BRAF pathway inhibition in IDH-wt GB. Overall, clinical efficacy is mostly described within case reports and umbrella trials, with promising but still insufficient results to draw more definitive conclusions. Further studies are needed to better define the molecular and phenotypic features that predict for a favorable response to treatment. In addition, limitations of B-Raf-inhibitors, in monotherapy or in combination with other therapeutic partners, to penetrate the blood-brain barrier and the development of acquired resistance mechanisms responsible for tumor progression need to be addressed.

The Evolving Role of Radiotherapy for Pediatric Cancers With Advancements in Molecular Tumor Characterization and Targeted Therapies

Ongoing rapid advances in molecular diagnostics, precision imaging, and development of targeted therapies have resulted in a constantly evolving landscape for treatment of pediatric cancers. Radiotherapy remains a critical element of the therapeutic toolbox, and its role in the era of precision medicine continues to adapt and undergo re-evaluation. Here, we review emerging strategies for combining radiotherapy with novel targeted systemic therapies (for example, for pediatric gliomas or soft tissue sarcomas), modifying use or intensity of radiotherapy when appropriate via molecular diagnostics that allow better characterization and individualization of each patient’s treatments (for example, de-intensification of radiotherapy in WNT subgroup medulloblastoma), as well as exploring more effective targeted systemic therapies that may allow omission or delay of radiotherapy. Many of these strategies are still under investigation but highlight the importance of continued pre-clinical and clinical studies evaluating the role of radiotherapy in this era of precision oncology.

Association of BRAF V600E mutations with vasoactive intestinal peptide syndrome in MYCN-amplified neuroblastoma

Very rarely, vasoactive intestinal peptide-related diarrhea (VIP-D) is observed in patients with high-risk neuroblastoma (HR-NB) where the associated fluid and electrolyte abnormalities can pose a major clinical challenge for administering the required aggressive multimodality treatment. Two patients with HR-NB developed VIP-D during induction and were found to have a somatic BRAF V600E mutation. Serum VIP levels and diarrhea promptly resolved in both patients after initiating treatment with BRAF and MEK inhibitors. This illustrates an association of VIP-D with BRAF V600E mutations and demonstrates a therapeutic strategy in the specific context of VIP-D and BRAF V600E mutations in HR-NB patients. The addition of BRAF and MEK inhibitors allows continued conventional tumor-directed treatment by decreasing the severity of symptoms caused by this life-threatening complication.

Diffuse leptomeningeal glioneuronal tumour (DLGNT) in children: the emerging role of genomic analysis

Diffuse leptomeningeal glioneuronal tumours (DLGNT) represent rare enigmatic CNS tumours of childhood. Most patients with this disease share common radiological and histopathological features but the clinical course of this disease is variable. A radiological hallmark of this disease is widespread leptomeningeal enhancement that may involve the entire neuroaxis with predilection for the posterior fossa and spine. The classic pathologic features include low- to moderate-density cellular lesions with OLIG2 expression and evidence of ‘oligodendroglioma-like’ appearance. The MAPK/ERK signaling pathway has recently been reported as a potential driver of tumourigenesis in up to 80% of DLGNT with KIAA1549:BRAF fusions being the most common event seen. Until now, limited analysis of the biological drivers of tumourigenesis has been undertaken via targeted profiling, chromosomal analysis and immunohistochemistry. Our study represents the first examples of comprehensive genomic sequencing in DLGNT and shows that it is not only feasible but crucial to our understanding of this rare disease. Moreover, we demonstrate that DLGNT may be more genomically complex than single-event MAPK/ERK signaling pathway tumours.

Inhibition of MEK pathway enhances the antitumor efficacy of chimeric antigen receptor T cells against neuroblastoma

Disialoganglioside (GD2)‐specific chimeric antigen receptor (CAR)‐T cells (GD2‐CAR‐T cells) have been developed and tested in early clinical trials in patients with relapsed/refractory neuroblastoma. However, the effectiveness of immunotherapy using these cells is limited, and requires improvement. Combined therapy with CAR‐T cells and molecular targeted drugs could be a promising strategy to enhance the antitumor efficacy of CAR T cell immunotherapy. Here, we generated GD2‐CAR‐T cells through piggyBac transposon (PB)‐based gene transfer (PB‐GD2‐CAR‐T cells), and analyzed the combined effect of these cells and a MEK inhibitor in vitro and in vivo on neuroblastoma. Trametinib, a MEK inhibitor, ameliorated the killing efficacy of PB‐GD2‐CAR‐T cells in vitro, whereas a combined treatment of the two showed superior antitumor efficacy in a murine xenograft model compared to that of PB‐GD2‐CAR‐T cell monotherapy, regardless of the mutation status of the MAPK pathway in tumor cells. The results presented here provide new insights into the feasibility of combined treatment with CAR‐T cells and MEK inhibitors in patients with neuroblastoma.

A circulating subset of BRAFV600E -positive cells in infants with high-risk Langerhans cell histiocytosis treated with BRAF inhibitors

BRAF inhibitors are an effective treatment for BRAF^V600E -mutated, risk-organ-positive Langerhans cell histiocytosis (RO⁺ LCH). However, cell-free BRAF^V600E DNA often persists during therapy and recurrence frequently occurs after therapy discontinuation. To identify a pathological reservoir of BRAF^V600E -mutated cells, we studied peripheral blood cells obtained from six infants with RO⁺ multisystem (MS) LCH that received targeted therapy. After cell sorting, the BRAF^V600E mutation was detected in monocytes (n = 5), B lymphocytes (n = 3), T lymphocytes (n = 2), and myeloid and plasmacytoid dendritic cells (n = 2 each). This biomarker may offer an interesting tool for monitoring the effectiveness of new therapeutic approaches for weaning children with RO⁺ LCH from targeted therapy.

A global approach to long-term follow-up of targeted and immune-based therapy in childhood and adolescence

While considerable efforts and progress in our understanding of the long-term toxicities of surgery, radiation and chemotherapy in children with cancer have been made over the last 5 decades, there continues to be a wide gap in our knowledge of the long-term health impact of most novel targeted and immunotherapy agents. To address this gap, ACCELERATE, a multi-stakeholder collaboration of clinical and translational academics, regulators from the EMA and FDA, patient/family advocates and members spanning small biotechnology through to large pharmaceutical companies have initiated the development of an international long-term follow-up data registry to collect this important information prospectively. Providing critical safety data on the long-term use of these approved and investigational therapies in children will support the regulatory requirements and labeling information. It will also provide the necessary insight to help guide physicians and families on the appropriateness of a targeted or immune therapy for their child and inform survivorship planning.

Precision medicine in pediatric solid cancers

Despite huge advances in the diagnosis and treatment of pediatric cancers over the past several decades, it remains one of the leading causes of death during childhood in developed countries. The development of new targeted treatments for these diseases has been hampered by two major factors. First, the extremely heterogeneous nature of the types of tumors encountered in this age group, and their fundamental differences from common adult carcinomas, has made it hard to truly get a handle on the complexities of the underlying biology driving tumor growth. Second, a reluctance of the pharmaceutical industry to develop products or trials for this population due to the relatively small size of the 'market', and a too-easy mechanism of obtaining waivers for pediatric development of adult oncology drugs based on disease type rather than mechanism of action, led to significant difficulties in getting access to new drugs. Thankfully, the field has now started to change, both scientifically and from a regulatory perspective, in order to address some of these challenges. In this review, we will examine some of the recent insights into molecular features which make pediatric tumors so unique and how these might represent therapeutic targets; highlight ongoing international initiatives for providing comprehensive, personalized genomic profiling of childhood tumors in a clinically-relevant timeframe, and look briefly at where the field of pediatric precision oncology may be heading in future.

Cutaneous melanoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Cutaneous melanoma is rare in children and, like other very rare pediatric tumors, it suffers from a shortage of knowledge and clinical expertise. The clinical management of pediatric melanoma is often challenging. Its clinical and pathological diagnosis may be difficult, and there is no standard treatment. In the absence of specific treatment guidelines, young patients are generally treated following the same principle as for adults, but concern remains about their access to clinical trials and new drugs, which have been shown to dramatically change the natural history of advanced melanoma. This paper presents the internationally recognized recommendations for the diagnosis and treatment of children and adolescents with cutaneous melanoma, established by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) within the EU-funded project called PARTNER (Paediatric Rare Tumours Network - European Registry). Main recommendations for melanoma are to discuss pediatric patients in multidisciplinary teams that include both pediatric oncologists and specialists in adult melanoma; to enroll patients in prospective trials, if available; to collect data in national-international databases; and to develop an effective international collaboration between pediatric and adult melanoma groups in order to facilitate the transfer of potentially effective new agents from the adult to the pediatric setting.

Opportunities and Challenges in Drug Development for Pediatric Cancers

The use of targeted small-molecule therapeutics and immunotherapeutics has been limited to date in pediatric oncology. Recently, the number of pediatric approvals has risen, and regulatory initiatives in the United States and Europe have aimed to increase the study of novel anticancer therapies in children. Challenges of drug development in children include the rarity of individual cancer diagnoses and the high prevalence of difficult-to-drug targets, including transcription factors and epigenetic regulators. Ongoing pediatric adaptation of biomarker-driven trial designs and further exploration of agents targeting non-kinase drivers constitute high-priority objectives for future pediatric oncology drug development. SIGNIFICANCE: Increasing attention to drug development for children with cancer by regulators and pharmaceutical companies holds the promise of accelerating the availability of new therapies for children with cancer, potentially improving survival and decreasing the acute and chronic toxicities of therapy. However, unique approaches are necessary to study novel therapies in children that take into account low patient numbers, the pediatric cancer genomic landscape and tumor microenvironment, and the need for pediatric formulations. It is also critical to evaluate the potential for unique toxicities in growing hosts without affecting the pace of discovery for children with these life-threatening diseases.

Paediatric Gliomas: BRAF and Histone H3 as Biomarkers, Therapy and Perspective of Liquid Biopsies

Simple Summary

Gliomas are major causes of worldwide cancer-associated deaths in children. Generally, paediatric gliomas can be classified into low-grade and high-grade gliomas. They differ significantly from adult gliomas in terms of prevalence, molecular alterations, molecular mechanisms and predominant histological types. The aims of this review article are: (i) to discuss the current updates of biomarkers in paediatric low-grade and high-grade gliomas including their diagnostic and prognostic values, and (ii) to discuss potential targeted therapies in treating paediatric low-grade and high-grade gliomas. Our findings revealed that liquid biopsy is less invasive than tissue biopsy in obtaining the samples for biomarker detections in children. In addition, future clinical trials should consider blood-brain barrier (BBB) penetration of therapeutic drugs in paediatric population.

Abstract

Paediatric gliomas categorised as low- or high-grade vary markedly from their adult counterparts, and denoted as the second most prevalent childhood cancers after leukaemia. As compared to adult gliomas, the studies of diagnostic and prognostic biomarkers, as well as the development of therapy in paediatric gliomas, are still in their infancy. A body of evidence demonstrates that B-Raf Proto-Oncogene or V-Raf Murine Sarcoma Viral Oncogene Homolog B (BRAF) and histone H3 mutations are valuable biomarkers for paediatric low-grade gliomas (pLGGs) and high-grade gliomas (pHGGs). Various diagnostic methods involving fluorescence in situ hybridisation, whole-genomic sequencing, PCR, next-generation sequencing and NanoString are currently used for detecting BRAF and histone H3 mutations. Additionally, liquid biopsies are gaining popularity as an alternative to tumour materials in detecting these biomarkers, but still, they cannot fully replace solid biopsies due to several limitations. Although histone H3 mutations are reliable prognosis biomarkers in pHGGs, children with these mutations have a dismal prognosis. Conversely, the role of BRAF alterations as prognostic biomarkers in pLGGs is still in doubt due to contradictory findings. The BRAF V600E mutation is seen in the majority of pLGGs (as seen in pleomorphic xanthoastrocytoma and gangliomas). By contrast, the H3K27M mutation is found in the majority of paediatric diffuse intrinsic pontine glioma and other midline gliomas in pHGGs. pLGG patients with a BRAF V600E mutation often have a lower progression-free survival rate in comparison to wild-type pLGGs when treated with conventional therapies. BRAF inhibitors (Dabrafenib and Vemurafenib), however, show higher overall survival and tumour response in BRAF V600E mutated pLGGs than conventional therapies in some studies. To date, targeted therapy and precision medicine are promising avenues for paediatric gliomas with BRAF V600E and diffuse intrinsic pontine glioma with the H3K27M mutations. Given these shortcomings in the current treatments of paediatric gliomas, there is a dire need for novel therapies that yield a better therapeutic response. The present review discusses the diagnostic tools and the perspective of liquid biopsies in the detection of BRAF V600E and H3K27M mutations. An in-depth understanding of these biomarkers and the therapeutics associated with the respective challenges will bridge the gap between paediatric glioma patients and the development of effective therapies.

Pediatric Melanoma-Diagnosis, Management, and Anticipated Outcomes

Melanoma is the most common skin cancer in children, often presenting in an atypical fashion. The incidence of melanoma in children has been declining. The mainstay of therapy is surgical resection. Sentinel lymph node biopsy often is indicated to guide therapy and determine prognosis. Completion lymph node dissection is recommended in selective cases after positive sentinel lymph node biopsy. Those with advanced disease receive adjuvant systemic treatment. Because children are excluded from melanoma clinical trials, management is based on pediatric retrospective data and adult clinical trials. This review focuses on epidemiology, presentation, surgical management, adjuvant therapy, and outcomes of pediatric melanoma.