Marked functional recovery and imaging response of refractory optic pathway glioma to BRAFV600E inhibitor therapy: a report of two cases

Dabrafenib for Pilocytic Astrocytoma With BRAF V599ins

This report highlights the first pediatric case of pilocytic astrocytoma with BRAF V599ins mutation, successfully treated with dabrafenib.

Successes and challenges in modeling heterogeneous BRAFV600E mutated central nervous system neoplasms

Central nervous system (CNS) neoplasms are difficult to treat due to their sensitive location. Over the past two decades, the availability of patient tumor materials facilitated large scale genomic and epigenomic profiling studies, which have resulted in detailed insights into the molecular underpinnings of CNS tumorigenesis. Based on results from these studies, CNS tumors have high molecular and cellular intra-tumoral and inter-tumoral heterogeneity. CNS cancer models have yet to reflect the broad diversity of CNS tumors and patients and the lack of such faithful cancer models represents a major bottleneck to urgently needed innovations in CNS cancer treatment. Pediatric cancer model development is lagging behind adult tumor model development, which is why we focus this review on CNS tumors mutated for BRAFV600E which are more prevalent in the pediatric patient population. BRAFV600E-mutated CNS tumors exhibit high inter-tumoral heterogeneity, encompassing clinically and histopathological diverse tumor types. Moreover, BRAFV600E is the second most common alteration in pediatric low-grade CNS tumors, and low-grade tumors are notoriously difficult to recapitulate in vitro and in vivo. Although the mutation predominates in low-grade CNS tumors, when combined with other mutations, most commonly CDKN2A deletion, BRAFV600E-mutated CNS tumors are prone to develop high-grade features, and therefore BRAFV600E-mutated CNS are a paradigm for tumor progression. Here, we describe existing in vitro and in vivo models of BRAFV600E-mutated CNS tumors, including patient-derived cell lines, patient-derived xenografts, syngeneic models, and genetically engineered mouse models, along with their advantages and shortcomings. We discuss which research gaps each model might be best suited to answer, and identify those areas in model development that need to be strengthened further. We highlight areas of potential research focus that will lead to the heightened predictive capacity of preclinical studies, allow for appropriate validation, and ultimately improve the success of "bench to bedside" translational research.

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.

Optic pathway glioma and endocrine disorders in patients with and without NF1

BACKGROUND

Optic pathway gliomas (OPGs) are classified by anatomic location and the association with neurofibromatosis type 1 (NF1). Children with OPGs face sequelae related to tumor location and treatment modalities. We assessed the prevalence of endocrine dysfunction in children with OPGs and compared outcomes between those with and without NF1.

METHODS

We performed a retrospective medical record review of medical history, and clinical and laboratory data, of children diagnosed with OPGs (n = 59, 61% with NF1) during 1990-2020, followed at a tertiary endocrine clinic. Growth and puberty parameters and occurrence of endocrine dysfunction were evaluated.

RESULTS

Isolated optic nerve involvement was higher among patients with than without NF1. Patients without NF1 were younger at OPG diagnosis and more often treated with debulking surgery or chemotherapy. At the last endocrine evaluation, patients without NF1 had comparable height SDS, higher BMI SDS, and a higher rate of endocrine complications (78.3% vs. 41.7%, p = 0.006). Younger age at diagnosis, older age at last evaluation, and certain OPG locations were associated with increased endocrine disorder incidence.

CONCLUSIONS

Endocrine dysfunction was more common in patients without NF1; this may be related to younger age at presentation, tumor locations, a greater progressive rate, and more aggressive treatments.

IMPACT

The literature is sparse regarding sporadic OPGs, and the mean duration of follow-up is shorter than at our study. Our data show a higher rate of endocrine dysfunction in patients with OPGs than previously described. We also found a higher prevalence of endocrine dysfunctions among patients without compared to those with NF-1. A better understanding of the true prevalence of endocrine disabilities that may evolve along time can help in guiding physicians in the surveillance needed in patients with OPG.

Early molecular diagnosis of BRAF status drives the neurosurgical management in BRAF V600E-mutant pediatric low-grade gliomas: a case report

BACKGROUND

To date, this is the only report showing with close and consecutive magnetic resonance images the extremely rapid response of two types of pediatric low-grade gliomas (PLGG) to vemurafenib and its impact on the surgical approach.

CASES PRESENTATION

We report two cases of symptomatic PLGG treated with vemurafenib, a BRAF inhibitor: in a 12-year-old girl it was used as first-line medical treatment, reducing the tumor by 45% within a month and stabilizing to 76% after a year; in a 3-year-old boy with no improvement after SIOP LGG 2004 Protocol, vemurafenib induced in only one week a 34% shrinkage and solved the hydrocephalus, avoiding surgical operation. DISCUSSION AND CONCLUSIONS: Our cases demonstrate how an early molecular diagnosis of BRAF mutations through the neurosurgical biopsy is essential to promptly start targeted therapies., whose effect can influence both therapeutic and surgical decisions, hopefully reducing the occurrence of second neurosurgery with associated risks of neurological sequelae.

Novel treatments in optic pathway gliomas

Optic pathway gliomas (OPG) are primary tumors of the optic nerve, chiasm, and/or tract that can be associated with neurofibromatosis type 1 (NF1). OPG generally have a benign histopathology, but a variable clinical course. Observation is generally recommended at initial diagnosis if vision is stable or normal for age, however, treatment may include chemotherapy, radiotherapy, or surgery in select cases. This manuscript reviews the literature on OPG with an emphasis on recent developments in treatment.

Cutaneous adverse events in children treated with vemurafenib for refractory BRAFV600E mutated Langerhans cell histiocytosis

BACKGROUND

The somatic BRAF^V600E mutation occurs in 38-64% of pediatric cases of Langerhans cell histiocytosis (LCH). Vemurafenib (VMF), a BRAF inhibitor, was approved for refractory BRAF^V600E mutated LCH. In adults, VMF causes frequent cutaneous adverse events (CAE) including skin tumors (squamous cell carcinomas, melanomas), but little is known in children. The objective of this study was to evaluate the frequency, clinical spectrum, and severity of CAEs in children treated with VMF for LCH. In addition, a correlation between CAE occurrence and VMF dose, residual plasma levels (RPLs), and efficacy was searched for.

PROCEDURE

Multicentric retrospective observational study including patients <18 years treated with VMF alone for refractory BRAF^V600E mutated LCH in 13 countries between October 1, 2013 and December 31, 2018.

RESULTS

Fifty-seven patients: 56% female, median age 2.1 years (0.2-14.6), median treatment duration 4.1 months (1.4-29.7). Forty-one patients (72%) had at least one CAE: photosensitivity (40%), keratosis pilaris (32%), rash (26%), xerosis (21%), and neutrophilic panniculitis (16%). No skin tumor was observed. Five percent of CAEs were grade 3. None were grade 4 or led to permanent VMF discontinuation. Dose reduction was necessary for 12% of patients, temporary treatment discontinuation for 16%, none leading to loss of efficacy. VMF dose, median RPL, and efficacy were not correlated with CAE occurrence.

CONCLUSIONS

At doses used for pediatric LCH, CAEs are frequent but rarely severe and have little impact on the continuation of treatment when managed appropriately. Regular dermatological follow-up is essential to manage CAEs and screen for possible induced skin tumors.

Cutaneous reactions to pediatric cancer treatment part II: Targeted therapy

Cancer remains a leading cause of morbidity and mortality among children. Targeted therapies may improve survivorship; however, unique side-effect profiles have also emerged with these novel therapies. Changes in hair, skin, and nails-termed dermatologic adverse events (AEs)-are among the most common sequelae and may result in interruption or discontinuation of therapy. Though dermatologic AEs have been detailed in adults, these findings are not well described in the pediatric population. We reviewed the literature to characterize dermatologic AEs to anticancer targeted therapies available as of July 2020 and summarized the spectrum of clinical findings as well as treatment recommendations for children. Dermatologic AEs are among the most common AEs reported in pediatric patients receiving targeted therapy, but morphologic and histologic descriptions are often lacking in current publications. Pediatric dermatologists are uniquely poised to recognize specific morphology of dermatologic AEs and make recommendations for prevention and treatment that may improve quality of life and enable ongoing cancer therapy.

Dual BRAF/MEK therapy in BRAF V600E-mutated primary brain tumors: a case series showing dramatic clinical and radiographic responses and a reduction in cutaneous toxicity

OBJECTIVE

BRAF V600E is a common oncogenic driver in a variety of primary brain tumors. Dual inhibitor therapy using dabrafenib (a selective oral inhibitor of several mutated forms of BRAF kinase) and trametinib (a reversible inhibitor of MEK1 and MEK2) has been used successfully for treatment of metastatic melanoma, anaplastic thyroid cancer, and other tumor types, but has been reported in only a few patients with primary brain tumors and none with pleomorphic xanthoastrocytoma. Here, the authors report on the substantial clinical response and reduction in cutaneous toxicity in a case series of BRAF V600E primary brain cancers treated with dual BRAF/MEK inhibitor therapy.

METHODS

The authors treated 4 BRAF V600E patients, each with a different type of primary brain tumor (pilocytic astrocytoma, papillary craniopharyngioma, ganglioglioma, and pleomorphic xanthoastrocytoma) with the combination of dabrafenib and trametinib.

RESULTS

The patients with pilocytic astrocytoma, pleomorphic xanthoastrocytoma, and papillary craniopharyngioma experienced near-complete radiographic and complete clinical responses after 8 weeks of therapy. A substantial partial response (by RANO [Response Assessment in Neuro-Oncology] criteria) was observed in the patient with ganglioglioma. The patient with craniopharyngioma developed dramatic, diffuse verrucal keratosis within 2 weeks of starting dabrafenib. This completely resolved within 2 weeks of adding trametinib.

CONCLUSIONS

Dual BRAF/MEK inhibitor therapy represents an exciting treatment option for patients with BRAF V600E primary brain tumors. In addition to greater efficacy than single-agent dabrafenib, this combination has the potential to mitigate cutaneous toxicity, one of the most common and concerning BRAF inhibitor-related adverse events.

Evaluating pediatric spinal low-grade gliomas: a 30-year retrospective analysis

PURPOSE

Most pediatric spinal tumors are low-grade gliomas (LGGs). Characterization of these tumors has been difficult given their heterogeneity and rare incidence. The objective was to characterize such tumors diagnosed at our institution.

METHODS

Spinal tumors diagnosed in our pediatric patients between 1984 and 2014 were reviewed retrospectively. Demographics, presentation, pathology, imaging, management, and sequelae were examined.

RESULTS

Forty patients had spinal LGG tumors, 24 (62%) of which were pilocytic astrocytomas. The most common initial presentations were pain (n = 15), partial extremity paralysis (n = 13), and ataxia (n = 11), with the diagnosis frequently delayed by months (median = 5.9 months, range 4 days-6.2 years). Twenty-nine patients had some tumor resection, and 8 required adjuvant therapy with chemotherapy (n = 4) or radiation (n = 4) post-resection. Ten other patients received only biopsy for histologic diagnosis, who were treated with chemotherapy (n = 4) or radiation (n = 5) post biopsy. Tumor progression was noted in 16 patients (2 after gross-total resection; 10, partial resection; and 4, biopsy). During the evaluation period, 3 patients died secondary to tumor progression. BRAF status could have shortened progression-free survival: patients with BRAFV600E mutations (n = 3) all experienced progression within 10 months. Long-term sequelae of the disease/treatment were mostly residual neurologic deficits (paresthesia, paralysis), chemotherapy-induced hearing loss, and scoliosis.

CONCLUSIONS

Spinal LGG is a rare entity with significant long-term effects. Although surgery is the most common initial treatment option, more in-depth analysis of molecular biomarkers may improve stratification and prognostication.

Pilocytic astrocytomas: BRAFV600E and BRAF fusion expression patterns in pediatric and adult age groups

PURPOSE

Pilocytic astrocytomas (PCAs) are characterized by two dominant molecular alterations of the BRAF gene, i.e., BRAFV600E mutation and KIAA1549-BRAF fusions which show a differential pattern of frequency across different age-groups.

METHODS

Formalin-fixed paraffin-embedded tissues of 358 (pediatric 276 and adult 82) consecutive PCAs were evaluated for BRAFV600E mutation by Sanger sequencing and KIAA1549:BRAF fusion transcripts (KIAA1549:BRAF 16-9, KIAA1549:BRAF 15-9, and KIAA1549:BRAF 16-11) by reverse transcriptase polymerase chain reaction, which were correlated with different clinicopathological features.

RESULTS

BRAFV600E mutation was detected in 8.9% pediatric and 9.75% adult PCAs, whereas 41.1% and 25.7% of pediatric and adult cases showed KIAA1549-BRAF fusions respectively. BRAFV600E did not show any statistically significant correlation with any of the clinical parameters (age, location, and gender). KIAA1549:BRAF fusions showed a significant statistical association with the pediatric age group and cerebellar location. KIAA1549-BRAF 16-9 was the commonest variant and was predominantly associated with cerebellar location than non-cerebellar whereas fusion variant 15-9 negatively correlated with cerebellar locations.

CONCLUSIONS

The present study showed overall frequency of 53.5% and 37.3% BRAF alterations in pediatric and adult PCA cases respectively. BRAF fusion in PCA cases showed a different distribution pattern across age groups and locations; while no such differential pattern was observed for BRAFV600E.