Diabetic Macular Edema In Black Patients Less Responsive To Bevacizumab

Black patients with diabetic macular edema (DME) are half as likely as their white or Hispanic peers to show short-term improvement in visual acuity after bevacizumab treatment, new findings show.

About a third of Black patients had improved visual acuity after three injections of the vascular endothelial growth factor (VEGF) inhibitor, compared to more than half of Hispanic and white patients, Dr. Manju Subramanian of Boston University School of Medicine and her colleagues report in the American Journal of Ophthalmology.

"This is the first study that looks directly at race as a factor affecting treatment response," Dr. Subramanian, an associate professor of ophthalmology, told Reuters Health by phone. "African Americans will benefit from it, just not to the same extent as whites and Hispanics, at least in the short term."

Black individuals are more than twice as likely as whites to develop clinically significant DME, regardless of hemoglobin A1C values and diabetes duration, Dr. Subramanian and her team note in their report. Intravitreal injections of angiogenesis inhibitors are now the standard of care for DME, they add, but studies supporting their benefit were done largely in white patients.

The authors had observed anecdotally that Black DME patients seemed to have worse outcomes with bevacizumab treatment than whites. A post hoc analysis of the Diabetic Retinopathy Clinical Research Network Protocol T published in 2018 also suggested worse visual outcomes in Black patients, but a greater reduction in central macular thickness (CMT).

To investigate, Dr. Subramanian and her team analyzed the medical charts of 314 DME patients who had at least one injection of bevacizumab at their center and 151 who had three injections. After one injection, 27% of Black patients had an improvement in visual acuity of at least 0.1 on the LogMAR scale, compared to 39% of Hispanic patients and 50% of whites (P=0.002).

After three injections, 34% of Black patients, 55% of Hispanic patients and 59% of whites had improved visual acuity (P=0.02). The likelihood of having improved vision after one or three injections was not significantly different for Hispanic and white patients.

Reduction in CMT thickness was similar across the three groups after one or three injections.

Of the 87 patients who did not have improvement in visual acuity after their first injection, only 23% had improvement after the third injection. The 57 patients whose vision did improve after their first treatment had an 82% chance of maintaining that improvement.

"This trend was consistent among all racio-ethnic groups and suggests that a patient who did not improve after one injection may continue to not respond after a series of injections," Dr. Subramanian and her team write. Further studies would be required to substantiate this finding."

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Bevacizumab is often the first choice for treating DME in patients at Boston Medical Center, the authors note, as it is less expensive than aflibercept or ranibizumab.

The initial studies of bevacizumab for an ophthalmic indication were in patients with age-related macular degeneration, Dr. Subramanian notes, which primarily affects individuals of northern European heritage. If clinical trials of bevacizumab had enrolled more Black patients, she added, "we probably would have seen this gap sooner."

"We really should confirm these findings with a prospective study," she added.

—Anne Harding

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