Eric Shinohara, MD, MSCI
Last Modified: August 7, 2008
Dear OncoLink "Ask the Experts,"
My son has optic nerve glioma of his right eye. His doctor suggested that he should get proton beam therapy. Unfortunately it is not available in my country. Please let you know how this problem can be treated.
Thank you in advance.
Eric Shinohara, MD, MSCI Radiation Oncology Section Editor for OncoLink responds:
Most gliomas of the optic nerve and chiasm (where the two optic nerves come together and separate again inside the brain) are discovered before the age of 10 years. Surgery is the treatment of choice for gliomas of the optic nerve (as opposed to gliomas of the chiasm), particularly when there is profound visual loss or when there is significant protrusion of eyeballs (proptosis).
Radiation therapy for treatment of optic nerve and chiasmal gliomas remains controversial. Some radiation oncologists advocate deferring radiation in patients with no symptoms or in those with lesser visual disturbance until there are signs of disease progression (International Journal of Radiation Oncology Biology Physics 1993 Jan 15;25(2):215-25). Others recommend that radiation therapy be given early in the course of the disease to minimize the risk of visual deterioration (Cancer 1987 Oct 15;60(8):1847-55). Often chemotherapy is administered in an effort to defer the use of radiation therapy (Journal Neurosurgery 1985 Dec;63(6):862-6). Because of the beam characteristics, proton beam therapy may have an advantage over photon beam therapy in terms of normal tissue protection, when it is planned, set up, and delivered properly. A small study out of Loma Linda University suggested that proton therapy could spare more normal tissue in children with optic pathway gliomas compared with 3D conformal radiation, particularly in larger tumors ( Int J Radiat Oncol Biol Phys 1999 Dec 1;45(5):1117-26. ). However, this was a very small study comparing treatment plans (rather than actual clinical outcomes from the different types of treatment), and further studies of protons in this disease are needed.
In general, tumors of the optic nerve (intracranial as well as intraorbital) have an excellent prognosis following complete surgical excision and/or irradiation (Cancer 1988 Feb 15;61(4):635-42; Journal of Neurosurgery 1988 Jan;68(1):85-98). As always, you should discuss the case with your son's doctor.