Modulation of Radiation Induced Cataract Formation by Estradiol

Abstract

Abstract: : Purpose: Radiation-induced cataract formation continues to be a significant complication in radiotherapy patients. There is recent evidence suggesting that estrogen might play a role in preventing some types of cataracts. The purpose of this study is to determine the effect of estrogen on radiation-induced cataracts. Methods: Oophorectomized Sprague-Dawley rats (N=27)were treated with either estradiol or placebo and then irradiated with 15Gy using the Leksell Gamma Knife to the right orbit. The gamma knife allowed delivery of a very high dose of radiation to the right orbit, while delivering only a minimal dose to the contralateral orbit. Rats were subjected to visual examination on a weekly basis. After 90 days post-treatment lenses were examined with a slit lamp. After 6 months rats were sacrificed and lenses were evaluated for light transmission using light microscopy. Results: Cataract formation was not seen in either group in the non-irradiated left orbit. Twelve of 14 irradiated eyes showed cataract formation in the estradiol treated group while only 5 of 13 eyes developed cataracts in the placebo group. This was a statistically significant difference (p<0.02, Fischer's exact test) The average percent light transmission in the irradiated eye of the estradiol treated group was 42%, compared to 77% in the placebo group (p<0.001). Conclusion: These data suggest that estradiol may actually promote radiation induced cataractogenesis.

Keywords: 338 cataract • 538 radiation therapy • 390 drug toxicity/drug effects