1.Department of Neurosurgery, Primary Childrens Medical Center, University of Utah, Salt Lake City, Utah, USA
The pattern of growth can be either perineural or intraneural in nature. Those patients with NF1 tend to have a perineural growth pattern, whereas those patients who have sporadic OPG tend to have an intraneural growth pattern.
In patients who are asymptomatic and have small tumors that have been incidentally discovered, close observation is the most appropriate avenue. Patients with NF1 that are asymptomatic tend to have a more benign overall course and can be carefully observed. There have been reports in these patients of spontaneous regression of disease. A younger age at diagnosis, however, tends to portend a higher rate of growth over time, so these patients should be monitored very closely if observation is undertaken.
Chemotherapy is considered first-line therapy for OPGs that are symptomatic or those that have shown progressive growth while in the surveillance and observation arm in patients under 3 years of age. This treatment modality does not have the long-term cognitive and endocrinological sequelae seen with the other treatment arms (surgery, radiation). No single chemotherapeutic agent has been identified as the gold standard for the treatment of OPGs; however, the most widely used regimen stems from reports published by Packer et al. Their regimen consists of concurrent carboplatin and vincristine in a 10-week induction phase, followed by 48 weeks of maintenance carboplatin and vincristine. They saw good results with this combination, with a progression-free survival of 75% at 2 years and 50% at 5 years and evidence of regression of tumor in 63% of patients. Other reports describing favorable results with the use of cisplatin and etoposide and temozolomide have appeared in the literature; however, the Packer regimen still seems to be the most widely used to date.
Historically, radiation therapy was the treatment of choice for OPG; however, this treatment has fallen out of favor as the effects of radiation therapy on the developing brain, specifically the cognitive and endocrine sequelae of treatment, have been elucidated. These ill-effects have limited the usefulness of this treatment modality in early childhood, when this disease process tends afflict most patients. Currently, radiation therapy is reserved for treatment of progressive OPGs in children older than 5-7 years of age who have previously received chemotherapy; however, there is no good Class I data that compares this radiation therapy to other treatment modalities. Treatment of children between the ages of 7 and 10 with radiation as first-line therapy has not been fully evaluated. Children 10 years and older should be treated with radiation therapy at 45-50 Gy. Newer modalities of delivering radiotherapy, such as stereotactic radiotherapy and proton beam radiotherapy, are promising options for radiation therapy in children in that they direct specific beams of radiation to the affected sites, thereby lessening the effects on the entire nervous system and the associated side effects due to radiation while preserving effectiveness. The newer modalities have not been shown in large prospective trials to be superior to standard therapies, so final recommendations can not be made until further testing in a prospective fashion is performed.
Treatment of OPGs with surgical resection is controversial. By their nature, gliomas tend to infiltrate the surrounding structures, and, in most cases, only a subtotal resection can be accomplished. The location of these tumors necessitates that surgical resection will involve sacrificing visual pathway fibers, which can lead to visual impairment. For these reasons, surgical resection is usually limited to cases in which disease is confined to one optic nerve or is causing progressive blindness or disfiguring proptosis, or in those cases in which there is an exophytic chiasmatic component causing obstructive hydrocephalus. Surgical intervention is not generally indicated in those patients with NF1. These patients tend to have diffuse infiltrative disease that has a more benign overall course, with little progression of disease seen after 6 years of age and some reports of spontaneous regression.
Toba Niazi ; Marion L Walker
Nervous System: Optic nerve glioma
Atlas Genet Cytogenet Oncol Haematol. 2008-11-01
Online version: http://atlasgeneticsoncology.org/solid-tumor/5099/nervous-system-optic-nerve-glioma