A Study Comparing Two Carboplatin Containing Regimens for Children and Young Adults With Previously Untreated Low Grade Glioma

Low grade gliomas are the most common central nervous system (CNS) tumors in the pediatric population. They consist of a heterogeneous group of tumors that are classified as World Health Organization (WHO) grade I or II. This includes astrocytic, oligodendroglial, neuronal and mixed glial- neuronal tumors. The clinical behavior of these tumors varies according to location and histology. The cerebellum is the most common location for low grade gliomas, but they can also arise in the cerebrum, deep midline structures such as the hypothalamus, optic pathway and, less frequently, in the brainstem. Although the etiology of most childhood LGG is unknown, patients with Neurofibromatosis type 1 (NF-1) are one rare group predisposed to developing CNS tumors. NF-1 is an inherited disorder that affects the nervous system, eyes and skin. In addition, children are at an increased risk for developing optic pathway and hypothalamic low grade gliomas. Fifteen to-20% of NF-1 patients will develop these tumors, and they account for up to 70% of the tumors seen in this location. In half of patients with NF-1 and an optic pathway tumor, the patients are not symptomatic and the mass is found incidentally. Many optic gliomas in NF-1 patients follow an indolent course and stabilize without intervention. Patients are most commonly treated when there is deterioration in their vision or a symptomatic increase in the tumor size. Although the event free survival (EFS) has been reported to be similar between NF1 and non-NF1 patients, overall survival is higher in NF1 patients. Location, as it affects the extent of surgical resection, plays a key role in the prognosis of all patients with low grade gliomas. Complete surgical resection offers a 90% survival rate at 10 years with often no need for adjuvant chemotherapy or radiation. Unfortunately, a gross total resection is not always possible due to the location of the tumor and its proximity to vital structures in the brain. In patients with an incomplete resection, the 10 year EFS is up to 74% with radiation treatment. However, toxicity from radiation, especially in young children, is significant and includes neurocognitive delays, endocrinopathies, secondary malignancy, ototoxicity and vasculopathy. Therefore, most experts agree that the standard of care in young children is to treat low grade gliomas that require adjuvant therapy after surgical resection/biopsy, or whose tumors are not surgically resectable with chemotherapy first, in order to delay or avoid radiation. This is especially true in children with NF-1, where the risk of a secondary malignancy after radiation therapy can be as high as 50% in the lifetime of the child.