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Precision radiation therapy for optic nerve sheath meningiomas
T Y Eng1, N W Albright, G Kuwahara
1Department of Radiation Oncology, University of California, School of Medicine, San Francisco.
International Journal of Radiation Oncology, Biology, Physics
|January 1, 1992
Summary
A new radiation therapy technique precisely targets unilateral optic nerve sheath meningioma, significantly reducing radiation dose to surrounding healthy tissues and improving setup accuracy. This method offers a safer treatment option for optic nerve lesions.
Area of Science:
- Radiation Oncology
- Neurosurgery
- Ophthalmology
Background:
- Unilateral optic nerve sheath meningioma requires precise radiation therapy.
- Conventional techniques risk irradiating critical structures like the optic chiasm and contralateral optic nerve.
- Improved immobilization and beam delivery are needed to minimize radiation side effects.
Purpose of the Study:
- To present and evaluate a novel, precise radiation therapy technique for unilateral optic nerve sheath meningioma.
- To assess the dosimetric advantages and setup accuracy of the new technique compared to conventional methods.
- To demonstrate the efficacy of this technique in patients with optic nerve lesions.
Main Methods:
- A new technique using an immobilization device to align the optic nerve vertically.
- Employing three small, half-beam blocked fields for conformal radiation delivery.
- Comparison of irradiated tissue volumes and doses to critical structures (optic chiasm, contralateral optic nerve, pituitary) with conventional opposed lateral and wedged pair techniques.
- Analysis of setup errors using the new technique versus conventional setups.
Main Results:
- The new technique significantly reduced the irradiated tissue volume: 58 cm³ (80% isodose) and 18 cm³ (95% isodose) compared to 171 cm³ and 73 cm³ for opposed laterals.
- Doses to the pituitary and contralateral optic nerve were substantially lower (4% vs. 40-100% for opposed laterals).
- Superior setup accuracy was achieved: 92.5% of setups < 3 mm off, compared to 55% for conventional setups.
Conclusions:
- The presented radiation therapy technique offers superior precision and reduced radiation dose to critical structures for unilateral optic nerve sheath meningioma.
- This method demonstrates significant dosimetric benefits and improved setup accuracy, making it a recommended approach for localized optic nerve lesions requiring radiation.
- The technique holds promise for improving treatment outcomes and minimizing toxicity in patients with optic nerve tumors.