Safety monitoring in bevacizumab (Avastin) treatment: retinal function assessed by psychophysical (visual fields, colour vision) and electrophysiological (ERG/EOG) tests in two subgroups of patients

Abstract

Background: Bevacizumab (Avastin) has been used as off-label treatment for the specific inhibition of the vascular endothelial growth factor (VEGF). Although only intravenous administration of the drug is approved in combination therapy of colorectal carcinoma, promising short-term results have been reported about its intravitreal administration. However, VEGF is also known to exhibit neurotrophic capabilities. Therefore, blockage of all VEGF isoforms by bevacizumab could induce toxic effects. Missing randomized controlled studies and unclear long-term risks require further evaluation.

Methods: Intensified monitoring of bevacizumab treatment was performed in consecutive patients. In ten patients, the functional field score was calculated after obtaining Goldmann visual fields at baseline and 1 year after injection. The other subgroup was examined by means of EOG, ERG and colour testing at baseline and 4 months following treatment. Naka-Rushton plots were calculated to enable statements about retinal function. Lanthony desaturated D15 test was used for repeated colour testing.

Results: Baseline parameters already disclosed predominant cone dysfunction. Drug-related effects caused a significant improvement of visual acuity. There was no sign of clinically relevant retinal toxicity following the bevacizumab injection. No progression of visual field defects was seen within the follow-up of 1 year. Performance in EOG testing was affected by restricted fixation stability, but no parameter indicated deterioration within the 4-month-period.

Conclusions: Short-term results underline that intraocular bevacizumab injection promises to be not only a cost-effective, but safe treatment option. Assessed functional parameters as error scores (e.g., Lanthony) corresponded to the impaired retinal function which was presumed to be disease-related. Further long-term results have to confirm the good tolerability in repeated treatment.