Low grade astrocytoma in children under the age of three years: a report from the Canadian pediatric brain tumour consortium

Future perspective of targeted treatments in pediatric low-grade glioma (pLGG): the evolution of standard-of-care and challenges of a new era

While surgery, when possible, remains the mainstay of pediatric low-grade glioma (pLGG) management, adjuvant therapy has significantly evolved over time. Radiation therapy was commonly used in the late 1990s for tumors that could not be resected or recurred. This resulted in significant late morbidity in this population and mortality related to secondary malignancies and chronic health conditions. Chemotherapy became the mainstay of adjuvant therapy but children still experienced late morbidity secondary to exposure to multiple lines of treatment over time. Targeted therapies emerged after the identification of frequent genetic alterations in the mitogen activated protein kinase (MAPK) pathway including KIAA1549-BRAF fusions and BRAF-V600 mutations and the near universal upregulation of the MAPK pathway in these tumors. Both BRAF and MEK inhibitors have shown efficacy in the treatment of pLGG and have led to prolonged stability in some cases. Multiple phase III clinical trials are now comparing targeted therapy to standard-of-care chemotherapy regimens setting the stage for targeted therapy to replace chemotherapy as the first-line treatment in some cases. Targeted therapy, however, is not without its challenges. There are clear examples of resistance and mechanisms of resistance have not been fully elucidated. There is also no clear duration for these therapies and rebound growth is a well-known phenomenon especially in BRAF-V600 mutant tumors. Targeted therapies are also fairly recent developments and long-term toxicities and functional outcomes are still being monitored. Very young and adolescent/young adult LGGs also carry molecular features that may not be addressed by inhibition of the MAPK pathway. Adjuvant therapy for pLGG has evolved from radiation for all unresectable or residual tumors to molecularly driven targeted therapies with improved quality of life, late effects, and less off-target toxicities. While there is still much to learn in regard to newer targeted therapies for pLGG, the era of targeted therapies for pediatric LGG is upon us.

Profound clinical and radiological response to BRAF inhibition in a 2-month-old diencephalic child with hypothalamic/chiasmatic glioma

Infants with low-grade glioma (LGG) have a poor survival. BRAFV600E mutation has been identified in pediatric LGG; however, the use of BRAF inhibitors in infants has never been reported. A 2-month-old with V600E mutant hypothalamic/chiasmatic glioma progressed on chemotherapy resulting in profound visual loss, massive ascites, and diencephalic syndrome. Initiation of dabrafenib resulted in rapid and sustained disappearance of clinical symptoms and a profound sustained cytoreduction. BRAF inhibition was safely tolerated with dramatic clinicoradiological response, suggesting early targeted therapy is a viable option in infants with LGG. A re-evaluation of current management paradigms in this population is warranted to leverage the potential benefit of upfront-targeted therapies.

An integrative molecular and genomic analysis of pediatric hemispheric low-grade gliomas: an update

Hemispheric low-grade gliomas account for the second most common location in pediatric low-grade gliomas (PLGGs) after the cerebellum. The pathological spectrum includes gangliogliomas, dysembryoplastic neuroepithelial tumors (DNETs), diffuse astrocytomas, pilocytic astrocytomas, and pleomorphic xanthoastrocytomas (PXAs), among others. Clinically, hemispheric PLGGs represent a well-recognized cause of intractable epilepsy in children and adolescents. With an excellent long-term outcome, surgery remains the cornerstone and patients with gross total resection typically do not need any further therapies. The recent literature about hemispheric PLGGs was reviewed to provide an up-to-date overview of the molecular and cell biology of these tumors. Hemispheric PLGGs can harbor multiple alterations involving BRAFV600E, FGFR, NTRK, MYB/MYBL1, IDH, and BRAF-KIAA1549 fusions. However, the clinical significance of most of these alterations is still to be defined. The role of RAS/MAPK mutations and other alterations in hemispheric PLGGs is of interest from diagnostic, prognostic, and therapeutic perspectives. Molecular testing for these tumors should be encouraged, since the findings can have an important impact not only in prognosis but also in therapeutic strategies.