Slipped capital femoral epiphyses: A major on-target adverse event associated with FGFR tyrosine kinase inhibitors in pediatric patients

Targeting the RAS/MAPK pathway in children with glioma

PURPOSE

Pediatric gliomas are the most common brain tumor in children, encompassing both low-grade glioma (pLGG) and high-grade glioma (pHGG). Alterations in the RAS/MAPK pathway are the driver event in the majority of pLGG and account for a subset of pHGG. Identification of these alterations has resulted in the transition to targeted therapy as a treatment option.

RESULTS

In pLGG, multiple trials have demonstrated superior outcomes using targeted therapy compared to traditional chemotherapy regimens. This has transformed care for these patients over the past decade with targeted therapy moving into front-line treatment regimens in certain scenarios. Despite these advances, novel targeted therapy approaches continue to present unique challenges to patient care, including optimal duration of therapy, distinct toxicity profiles and the unknown potential impact on the natural history of disease. While targeted therapy has revolutionized treatment of pLGG, additional questions remain in regard to pHGG including the role of targeted therapy in combination with other treatments, such as chemotherapy/radiation, and mechanisms of resistance. These developments are promising treatment options for pediatrics gliomas, enabling a move towards precision medicine.

CONCLUSION

Herein, we review the role of RAS/MAPK targeted therapy for treatment of pediatric glioma along with the current controversies and outstanding questions.

Novel therapies for pediatric low grade glioma

PURPOSE OF REVIEW

Current biological findings provide new insights into the genetics driving growth of low-grade gliomas in pediatric patients. This has provided new targets for novel therapies. The purpose of this paper is to review novel therapies for pediatric low-grade gliomas that have been published in the past 24 months.

RECENT FINDINGS

Low-grade gliomas are often driven by mitogen activated protein kinase (MAPK) alterations either with BRAF V600E point mutations or BRAF fusions. Current advances have also highlighted novel fusions of fibroblast growth factor receptor (FGFR), myeloblastosis family of transcription factors (MYB), meningioma 1 tumor suppressor (MN1), neurotrophic receptor kinase family of receptors (NTRK), Kristen RAS (Rat Sarcoma Virus) oncogene homolog in mammals (KRAS), Receptor tyrosine kinase ROS proto oncogene 1 (ROS1), protein kinase C alpha (PRKCA), and platelet derive growth factor receptor (PDGFR) amplification. Novel therapies have been employed and are showing encouraging results in pediatric low-grade gliomas. Current trials are underway with newer generation pan RAF inhibitors and mitogen activated protein kinase - kinase (MEK) inhibitors. Other early phase clinical trials have provided safety data in pediatric patients targeting FGFR fusion, NTRK fusion, PDGFR amplification and ROS1 mutations.

SUMMARY

Historical treatment options in pediatric low-grade gliomas have utilized surgery, radiation therapy and conventional chemotherapy. Recently greater insight into their biology has found that alterations in MAPK driven pathways are often the hallmark of tumorigenesis. Targeting these novel pathways has led to tumor control and shrinkage without the use of conventional chemotherapy. Caution should be taken however, since these treatment options are still novel, and we do not fully appreciate the long-term effects. Nonetheless a new era of targeted medicine is here.

How modern treatments have modified the role of surgery in pediatric low-grade glioma

Low-grade gliomas are the most common brain tumor of childhood, and complete resection offers a high likelihood of cure. However, in many instances, tumors may not be surgically accessible without substantial morbidity, particularly in regard to gliomas arising from the optic or hypothalamic regions, as well as the brainstem. When gross total resection is not feasible, alternative treatment strategies must be considered. While conventional chemotherapy and radiation therapy have long been the backbone of adjuvant therapy for low-grade glioma, emerging techniques and technologies are rapidly changing the landscape of care for patients with this disease. This article seeks to review the current and emerging modalities of treatment for pediatric low-grade glioma.

Case report: Slipped capital femoral epiphysis: a rare adverse event associated with FGFR tyrosine kinase inhibitor therapy in a child

We report a case of slipped capital femoral epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. A 13-year-old boy was diagnosed to have an optic pathway/hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD). He developed hypothalamic obesity with rapid weight gain and BMI >30. At 12 weeks of treatment with erdafitinib, he developed persistent knee pain. X-ray of the right hip showed SCFE. Erdafitinib was discontinued, and he underwent surgical pinning of the right hip. MRI at discontinuation of erdafitinib showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow-up. Our experience and literature review suggest that pediatric patients who are treated with pan-FGFR TKIs should be regularly monitored for skeletal side effects.

Feasibility and antitumour activity of the FGFR inhibitor erdafitnib in three paediatric CNS tumour patients

Alterations of the fibroblast growth factor (FGF) signalling pathway are increasingly recognized as frequent oncogenic drivers of paediatric brain tumours. We report on three patients treated with the selective FGFR1-4 inhibitor erdafitinib. Two patients were diagnosed with a posterior fossa ependymoma group A (PFA EPN) and one with a low-grade glioma (LGG), harbouring FGFR3/FGFR1 overexpression and an FGFR1 internal tandem duplication (ITD), respectively. While both EPN patients did not respond to erdafitinib treatment, the FGFR1-ITD-harbouring tumour showed a significant decrease in tumour volume and contrast enhancement throughout treatment. The tumour remained stable 6 months after treatment discontinuation.

Pediatric low-grade glioma: State-of-the-art and ongoing challenges

The most common childhood central nervous system (CNS) tumor is pediatric low-grade glioma (pLGG), representing 30%-40% of all CNS tumors in children. Although there is high associated morbidity, tumor-related mortality is relatively rare. pLGG is now conceptualized as a chronic disease, underscoring the importance of functional outcomes and quality-of-life measures. A wealth of data has emerged about these tumors, including a better understanding of their natural history and their molecular drivers, paving the way for the use of targeted inhibitors. While these treatments have heralded tremendous promise, challenges remain about how to best optimize their use, and the long-term toxicities associated with these inhibitors remain unknown. The International Pediatric Low-Grade Glioma Coalition (iPLGGc) is a global group of physicians and scientists with expertise in pLGG focused on addressing key pLGG issues. Here, the iPLGGc provides an overview of the current state-of-the-art in pLGG, including epidemiology, histology, molecular landscape, treatment paradigms, survival outcomes, functional outcomes, imaging response, and ongoing challenges. This paper also serves as an introduction to 3 other pLGG manuscripts on (1) pLGG preclinical models, (2) consensus framework for conducting early-phase clinical trials in pLGG, and (3) pLGG resistance, rebound, and recurrence.