Dose of intravitreal bevacizumab (Avastin) used as preoperative adjunct therapy for proliferative diabetic retinopathy

Abstract

Purpose: The purpose of this study was to examine the effect of lower than usual doses of intravitreal bevacizumab (Avastin) on vitreous vascular endothelial growth factor (VEGF) concentration and intraoperative bleeding when used as preoperative adjunct therapy in patients undergoing vitrectomy for proliferative diabetic retinopathy.

Methods: Fifty-two eyes (52 patients) with indications for vitrectomy were studied; 12 received bevacizumab, and 40 did not. The bevacizumab group was given a single intravitreal injection of bevacizumab (0.16-1.25 mg) 3 days before vitrectomy. Numbers of intraoperative coagulation spots administered for hemostasis were compared between the two groups. In both groups, vitreous samples were collected during vitrectomy, and VEGF levels were measured by enzyme-linked immunosorbent assay.

Results: The VEGF concentration was 1880.1 +/- 1927.5 in the nonbevacizumab group and 24.9 +/- 25.1 in the bevacizumab group, and the difference was significant (P = 0.0001). Although VEGF concentrations were apparently lower at higher bevacizumab doses, no significant correlation was observed (r = 0.366, P = 0.2425). Numbers of intraoperative coagulation spots differed significantly between the bevacizumab (3.2 +/- 0.8) and nonbevacizumab (5.7 +/- 1.0) groups (P < 0.0001). In the bevacizumab group, there was no correlation between the number of intraoperative coagulation spots and the bevacizumab dose (r = 0.272, P = 0.3919).

Conclusion: When intravitreal bevacizumab was administered as preoperative adjunct therapy to patients undergoing vitrectomy for proliferative diabetic retinopathy, the lowest dose tested (0.16 mg) was as effective as the standard dose (1.25 mg) in reducing vitreous VEGF concentrations and also decreasing intraoperative bleeding as measured by the reduced number of coagulation spots.