A new study suggests clinicians may know by week 12 if a patient is likely to achieve positive visual benefits from anti-vascular endothelial growth factor (VEGF) therapy. Researchers used data from the Protocol I study to better understand the short and long-term effects of ranibizumab plus prompt laser and ranibizumab plus deferred laser treatment.

Of the 335 eyes included in the study, 118 showed less than 20% central retinal thickness (CRT) reduction and 217 had more than 20% CRT reduction at 12 weeks post-treatment. During the three-year follow-up, 83.9% and 82.9% of the strong responders maintained the initial 20% or more CRT reduction at 52 and 156 weeks, respectively. Of the limited responders, only 31.4% and 51.7% subsequently achieved a 20% or more CRT reduction by 52 and 156 weeks, respectively.

While the data is promising for the treatment as a whole, only two-thirds of patients achieved a 20% CRT reduction or more within three months of therapy, and the remaining patients only had a limited response. For the limited responders, prospects for further improvement with treatment were moderate, at best, according to the study, with nearly half of these patients continuing to show a less than 20% CRT reduction at three years.

“This would imply that resolution of macular edema after an initially limited treatment response is less readily achievable than maintenance of remission after a strong early treatment response,” the study says. 

Even for the few limited responders who finally achieved a 20% or more reduction of CRT, the process was slow, the researchers added. “Although a limited early CRT response to ranibizumab does not preclude further anatomical improvement with continued treatment, consolidation of the anatomical response in these circumstances is generally protracted and falls short of the therapeutic objective of achieving timely elimination of subretinal and intraretinal fluid,” the study concludes.

The findings may help clinicians better counsel patients failing to achieve a 20% CRT reduction within 12 weeks of treatment, the study says. Although a positive response isn’t out of the question in the long run, the patient may want to consider additional disease management strategies.

Dugel PU, Campbell JH, Kiss S, et al. Association between early anatomic response to anti-vascular endothelial growth factor therapy and long-term outcome in diabetic macular edema: an independent analysis of Protocol I study data. Retina. 2019;39(1):88-97.