Drug Dosages Questioned in Diabetic Macular Edema Trial

by: Laird Harrison
VIENNA — Differences in dosing could explain why aflibercept produced better results in patients with diabetic macular edema than ranibizumab or bevacizumab in a recent trial, experts say.
“Bevacizumab or ranibizumab at higher doses may be equivalent, although that is not technically easy with either drug,” David Brown, MD, from the Baylor College of Medicine in Houston, Texas, told Medscape Medical News.
The point arose after a presentation here at the American Society of Retina Specialists (ASRS) 2015 Annual Meeting of results from the Protocol T comparison study conducted by the Diabetic Retinopathy Clinical Research Network. The results were also published in the New England Journal of Medicine(2015;372:1193-1203).
In the Protocol T study, researchers randomly assigned 660 people with diabetic macular edema to intravitreal injections: 224 received aflibercept 2.0 mg, 218 received bevacizumab 1.25 mg, and 218 received ranibizumab 0.3 mg.
The mean age of the study participants was 61 years.
All patients had at least one eye with a best corrected visual acuity letter score of 78 to 24 on a 100-point scale. Higher scores indicated better visual acuity. The equivalent range on the Snellen chart would be 20/32 to 20/320.
All patients had center-involved diabetic macular edema evident on clinical examination and optical coherence tomography.
A year after treatment, patients in the aflibercept group had gained more lines of vision than those in the bevacizumab and ranibizumab groups. However, that difference was entirely attributed to the patients in each group who had the most severe vision loss.
Table. Change in Letters of Visual Acuity at 1 Year

Baseline Letter Score Snellen Equivalent Aflibercept Group Bevacizumab Group Ranibizumab Group
≤69 ≤20/50 18.9 11.8 14.2
78 – 69 20/32 – 20/40 8.0 7.5 8.3

For patients with 20/50 visual acuity or worse, the difference between aflibercept and bevacizumab was significant (P = .001), as was the difference between aflibercept and ranibizumab (P = .003). However, the difference between bevacizumab and ranibizumab was not significant (P = .21)……..
Read more: http://www.medscape.com/viewarticle/848287
Source: Medscape