Analysis of Vision loss caused by radiation-induced optic neuropathy after particle therapy for head-and-neck and skull-base tumors adjacent to optic nerves.
OBJECTIVE
To assess the incident rates of vision loss (VL; based on counting fingers or more severe) caused by radiation-induced optic neuropathy (RION) after particle therapy for tumors adjacent to optic nerves (ONs), and to evaluate factors that may contribute to VL.


METHODS
From August 2001 to August 2006, 104 patients with head-and-neck or skull-base tumors adjacent to ONs were treated with carbon ion or proton radiotherapy. Among them, 145 ONs of 75 patients were irradiated and followed for greater than 12 months. The incident rate of VL and the prognostic factors for occurrence of VL were evaluated. The late effects of carbon ion and proton beams were compared on the basis of a biologically effective dose at alpha/beta = 3 gray equivalent (GyE(3)).


RESULTS
Eight patients (11%) experienced VL resulting from RION. The onset of VL ranged from 17 to 58 months. The median follow-up was 25 months. No significant difference was observed between the carbon ion and proton beam treatment groups. On univariate analysis, age (>60 years), diabetes mellitus, and maximum dose to the ON (>110 GyE(3)) were significant, whereas on multivariate analysis only diabetes mellitus was found to be significant for VL.


CONCLUSIONS
The time to the onset of VL was highly variable. There was no statistically significant difference between carbon ion and proton beam treatments over the follow-up period. Based on multivariate analysis, diabetes mellitus correlated with the occurrence of VL. A larger study with longer follow-up is warranted.
Department of Radiology, Hyogo Ion Beam Medical Center, Tatsuno, Hyogo, Japan. y_demizu@nifty.com
Yusuke
Y
Demizu
Masao
M
Murakami
Daisuke
D
Miyawaki
Yasue
Y
Niwa
Takashi
T
Akagi
Ryohei
R
Sasaki
Kazuki
K
Terashima
Daisaku
D
Suga
Isao
I
Kamae
Yoshio
Y
Hishikawa
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002250:Carbon Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009900:Optic Nerve / Q000528:radiation effects*; D009901:Optic Nerve Diseases / Q000209:etiology*; D061766:Proton Therapy; D011522:Protons / Q000009:adverse effects; D011832:Radiation Injuries / Q000150:complications*; D012062:Relative Biological Effectiveness; D019292:Skull Base Neoplasms / Q000532:radiotherapy*; D014786:Vision Disorders / Q000209:etiology*; D055815:Young Adult
D002250:Carbon Radioisotopes; D011522:Protons