Although first defined as benign hamartomatous growths in 1969 by Hoyt and Baghdassarian [
8], optic gliomas are low grade tumors that progress locally or cause death in 75% of patients if left untreated [
5]. The most important factor in patients with optic glioma is the extent of disease at the time of diagnosis [
3,
8]. In large series from the Mayo Clinic [
9] with a median follow-up time of 10 years, patients with glioma confined to the optic nerve survived almost twice as long as those with involvement of optic chiasm. Total surgical resection of the tumors limited to optic nerve only, leads to high long term survival up to 100% of 15 year progression free survival [
3]. Radiotherapy in the management of chiasmal lesions produce local control and survival advantage when compared to biopsy only [
5,
10-
12]. Tenny et al. [
10] reported that only 3/14 (21%) patients with chiasmal gliomas survived following biopsy only when compared to 28/44 (64%) survival after radiotherapy. The majority of our patients included in the statistical analysis (18/21) had tumors involving chiasma and radiotherapy produced 93% 10 year overall and 84% progression free survival which is consistent with Kovalic et al. [
3]. The presence of neurofibromatosis in optic glioma patients has been suggested as a favorable prognostic sign [
3,
13]. Only 4/16 patients in our series had neurofibromatosis and these patients were without any sign of progression at the time of analysis. Since only four patients were with neurofibromatosis, we could not estimate a prognostic value in this regard.
Radiation doses lower than 5000 cGy are reported to be associated with significantly lower progression free and overall survival rates [8]. Only two patients who are younger than three years at the time of irradiation in our series received 4500 cGy. The remaining nineteen patients were treated with doses equal or more than 5000 cGy. Two patients in our series developed local recurrences. These patients were with tumors extending hypothalamus or the third ventricle and 5000 cGy external irradiation was applied. Since most of our patients received more than 5000 cGy, it is difficult to make a conclusion about the dose effect.
Radiotherapy leads to 9-44% of improved vision and 77% stable vision (1,14). Eight patients (42%) in our series were reported to have improved vision while 11 patients (58%) showed stable vision after radiotherapy which is consistent with the literature.
In conclusion, optic pathway gliomas involving chiasma and contiguous structures should be referred for radiotherapy either after debulking surgery or biopsy or clinical diagnosis. Our treatment policy is to treat these tumors with doses above 5000 cGy.
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