Protocol T extension study details 5-year outcomes after anti-VEGF for DME

This study assessed 5-year outcomes in eyes initially treated with anti-VEGF therapy for central-involved diabetic macular edema (DME) during a 2-year study.

Study design

This is an extension of a multicenter, randomized, clinical trial (Protocol T) conducted by the DRCR Retina Network, which compared aflibercept, bevacizumab and ranibizumab for the treatment of eyes with visual impairment secondary to central-involved DME. Following the initial 2-year study, 317 interested participants were managed at the clinical discretion of the treating physician and recalled at 5 years for repeat testing. Charts were reviewed for medical and ocular history during years 2 to 5.

Outcomes

At 5 years, mean vision improved by 7.4 letters from baseline, despite a 4.7-letter decline between years 2 and 5. Mean central subfield thickness decreased by 154 μm from baseline to 5 years, but was stable between years 2 and 5.

Limitations

This study only included 68% of the potential cohort and 48% of the original cohort. In addition, follow-up visits and treatment data in the interval between years 2 and 5 were extracted from chart reviews and may be incomplete.

Clinical significance

The decline in visual acuity that occurred in this extension study when switching from a strict study protocol to standard of care reinforces what other studies have told us in the past. In clinical practice, patients tend to be treated less frequently due to various factors and this often impacts visual acuity. This may suggest that closer monitoring or more aggressive treatment regimens may be needed to maintain visual gains. Interestingly, central subfield thickness did not show a corresponding increase in this trial.