Does altered fractionation influence the risk of radiation-induced optic neuropathy?
OBJECTIVE
To analyze the parameters that influence the risk of radiation-induced optic neuropathy (RION) after radiotherapy for head-and-neck tumors.


METHODS
Between 1964 and 2000, 273 patients with tumors of the nasopharynx, paranasal sinuses, nasal cavity, and hard palate adenoid cystic carcinomas were treated with curative intent and had radiation fields that included the optic nerves and/or chiasm. Patients were followed for at least 1 year after radiotherapy.


RESULTS
Radiation-induced optic neuropathy developed in 32 eyes of 24 patients (9%). The 5-year rates of freedom from RION according to the total dose and once- vs. twice-daily fractionation were as follows: < or =63 Gy once daily, 95%; < or =63 Gy twice daily, 98%; >63 Gy once daily, 78%; and >63 Gy twice daily, 91%. Multivariate analysis revealed that the total dose affected the risk of RION (p = 0.0047), with patient age (p = 0.0909), once-daily vs. twice-daily fractionation (p = 0.0684), and overall treatment time (p = 0.0972) were marginally significant. The use of adjuvant chemotherapy did not significantly influence the likelihood of developing RION.


CONCLUSIONS
The likelihood of developing RION is primarily influenced by the total dose. Hyperfractionation may reduce the risk of experiencing this complication.
Department of Radiation Oncology, Health Science Center, University of Florida College of Medicine, Gainesville, FL 32610, USA.
Niranjan
N
Bhandare
Alan T
AT
Monroe
Christopher G
CG
Morris
M Tariq
MT
Bhatti
William M
WM
Mendenhall
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000704:Analysis of Variance; D019583:Dose Fractionation, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D009900:Optic Nerve / Q000528:radiation effects*; D009901:Optic Nerve Diseases / Q000188:drug therapy / Q000209:etiology*; D011832:Radiation Injuries / Q000188:drug therapy / Q000209:etiology*; D018570:Risk Assessment
D000305:Adrenal Cortex Hormones