Long-term evaluation of radiation-induced optic neuropathy after single-fraction stereotactic radiosurgery.
OBJECTIVE
To determine the long-term risk of radiation-induced optic neuropathy (RION) in patients having single-fraction stereotactic radiosurgery (SRS) for benign skull base tumors.


METHODS
Retrospective review of 222 patients having Gamma Knife radiosurgery for benign tumors adjacent to the anterior visual pathway (AVP) between 1991 and 1999. Excluded were patients with prior or concurrent external beam radiation therapy or SRS. One hundred twenty-nine patients (58%) had undergone previous surgery. Tumor types included confirmed World Health Organization grade 1 or presumed cavernous sinus meningioma (n=143), pituitary adenoma (n=72), and craniopharyngioma (n=7). The maximum dose to the AVP was ≤8.0 Gy (n=126), 8.1-10.0 Gy (n=39), 10.1-12.0 Gy (n=47), and >12 Gy (n=10).


RESULTS
The mean clinical and imaging follow-up periods were 83 and 123 months, respectively. One patient (0.5%) who received a maximum radiation dose of 12.8 Gy to the AVP developed unilateral blindness 18 months after SRS. The chance of RION according to the maximum radiation dose received by the AVP was 0 (95% confidence interval [CI] 0-3.6%), 0 (95% CI 0-10.7%), 0 (95% CI 0-9.0%), and 10% (95% CI 0-43.0%) for patients receiving ≤8 Gy, 8.1-10.0 Gy, 10.1-12.0 Gy, and >12 Gy, respectively. The overall risk of RION in patients receiving >8 Gy to the AVP was 1.0% (95% CI 0-6.2%).


CONCLUSIONS
The risk of RION after single-fraction SRS in patients with benign skull base tumors who have no prior radiation exposure is very low if the maximum dose to the AVP is ≤12 Gy. Physicians performing single-fraction SRS should remain cautious when treating lesions adjacent to the AVP, especially when the maximum dose exceeds 10 Gy.
Department of Ophthalmology, Mayo Clinic and Foundation, Rochester, Minnesota. Electronic address: leavitt.jacqueline@mayo.edu.
Jacqueline A
JA
Leavitt
Scott L
SL
Stafford
Michael J
MJ
Link
Bruce E
BE
Pollock
D000236:Adenoma / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003397:Craniopharyngioma / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008577:Meningeal Neoplasms / Q000601:surgery; D008579:Meningioma / Q000601:surgery; D008875:Middle Aged; D009900:Optic Nerve / Q000528:radiation effects*; D010911:Pituitary Neoplasms / Q000601:surgery; D011832:Radiation Injuries / Q000453:epidemiology*; D011836:Radiation Tolerance; D016634:Radiosurgery / Q000009:adverse effects* / Q000379:methods; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D018570:Risk Assessment; D019292:Skull Base Neoplasms / Q000601:surgery*; D055815:Young Adult