Radiation has potential in age-related macular degeneration

November 1, 2010

Epimacular brachytherapy seems to be a safe and effective approach for treating neovascular age-related macular degeneration based on the 36-month results of the NVI-III pilot study, according to one expert.

The patients were followed for 3 years and had a mean increase in visual acuity of 3.5 letters at the 3-year evaluation and a mean gain of 12 letters following cataract surgery. Importantly, 58% did not require a re-treatment with bevacizumab (Avastin, Genentech) at the same time point, which lessened the treatment burden.

The optimal treatment for neovascular AMD has not yet been determined, and the currently administered monthly injections of anti-vascular endothelial growth factor (VEGF) agents are the gold standard. Combination therapies have many clear-cut advantages including reducing the frequency and overall number of injections while maintaining or improving on the visual results of monthly injections, according to Dr. Boyer, who is in private practice in Los Angeles.

Pilot study

The nonrandomized NVI-111 study is a 3-year evaluation of the safety and efficacy of epimacular brachytherapy (strontium 90) plus bevacizumab. Following pars plana vitrectomy, the investigators used a novel device (Vidion ANV Therapy System, NeoVista Inc.) to deliver one dose of radiation to the retina. To minimize damage to healthy retinal tissue, they used a 20-gauge cannula to focus the radiation on the neovascular AMD. The radiation dose was 24 Gy in all patients.

Thirty-four patients, among whom all lesion types were present, were originally enrolled at two study sites in Brazil (São Paulo [n = 14] and Goiâna [n = 19]) and one in Guadalajara, Mexico (n = 1) from June 2006 to April 2007. The patients in Mexico and São Paulo have been followed for 2 years; the patients in Goiâna have been followed for 3 years and were reported by Dr. Boyer.

All patients received two injections of 1.25 mg of bevacizumab during the study, but at different time points. One injection of bevacizumab was administered to one group of patients 10 days before vitrectomy, and one injection of the drug was administered after they were treated with radiation. The second injections were administered 1 month after surgery for both groups.

Of the study patients, 65% were women, and most patients (71%) were phakic. Fifty percent of patients had occult AMD, 29% predominantly classic AMD, and 21% minimally classic AMD.

The mean best-corrected visual acuity (BCVA) of the 19 patients who were followed for 3 years was 20/160. Of those 19 patients, 74% were women; 53% had occult AMD, 37% predominately classic AMD, and 10% minimally classic AMD.

Four device-related adverse events occurred (i.e., one retinal tear, one subretinal hemorrhage, one case of subretinal fibrosis, and one case of nonproliferative radiation retinopathy).

Procedure-related adverse events included 12 cases of cataract, two of retinal fibrosis, and one of epiretinal membrane.

Dr. Boyer said that 1 year after treatment, all patients (n = 19) had lost fewer than 15 letters of visual acuity. That decreased to 68% by 2 years and increased to 90% at 3 years, with patients undergoing surgery after 24 months.

At the 3-year evaluation, 53% of patients had gained one or more letters of visual acuity, and 21% had gained 15 letters or more, he said.

"Overall, the patients had a mean increase in visual acuity of 3.5 letters at 3 years, and a mean gain of 12 letters following cataract surgery," Dr. Boyer said.

At the 1-year evaluation, he said, 91% of patients had not required a re-treatment with bevacizumab; 79% did not require a re-treatment at 2 years; and 58% did not require a re-treatment at 3 years. After the first 2 mandatory injections, only a mean of 1.2 injections were given in the p.r.n. phase.

"The procedure had a good safety record and resulted in minimal surgical complications," Dr. Boyer said. "A downside to the treatment was the accelerated cataract formation as a result of vitrectomy.

"In the patient who developed the radiation retinopathy, the baseline visual acuity of 20/50 improved at 24 months to 20/40, and increased again to 20/32 at the 3-year time point," he said. "By 43 months, the vision had decreased to 20/40 and no re-treatments were required. The efficacy results suggested that the treatment effect is durable over the long term, and most patients required no re-treatments at 3 years."

FYI

David S. Boyer, MD
E-mail: vitdoc@aol.com

Dr. Boyer has no financial interest in the technology. The NeoVista system will be evaluated in the larger, randomized, prospective CABERNET study, which has completed enrollment of 492 patients.