Science & Technology

About the NeoVista procedure

At present, the standard of care for wet AMD is the intravitreal injection of anti–vascular endothelial growth factor (anti-VEGF) medication. This therapy helps control choroidal neovascularization (CNV) and stabilize vision. Like anti-VEGF therapy, beta radiation therapy affects the abnormal blood vessels of wet AMD by slowing the development of new vessels and reducing inflammation, allowing the macula to return to its normal position. Unlike standard therapy, however, the NeoVista procedure is only performed once, and patients receive only two doses of an anti-VEGF drug.

The treatment being used in the pivotal study utilizes a typical vitrectomy, with radiation delivered using the NeoVista system. Patients usually require only local anesthesia, and the entire procedure normally takes less than 1 hour.

Radiation delivery using the NeoVista device is highly focal, penetrating the target area to a depth of only 3 mm and covering an area slightly larger than 5 mm in diameter. Because beta radiation dissipates very rapidly, surrounding normal tissues are less affected than with other forms of radiation used in older treatments. Thus, application is not only more accurate but more localized. This helps to reduce the risk of radiation-induced toxicity significantly.

The full-body radiation dose received by the patient is less than the dose received during a typical chest x-ray. The surgeon and others in the operating theater also receive minimal exposure.

Clinical studies show promise

Recently reported 18-month data from a concomitant-use Phase II study have shown that the effect of NeoVista epimacular beta radiation therapy is potentially lasting and safe. This study investigated the safety and efficacy of NeoVista treatment in conjunction with 2 injections of Avastin® (bevacizumab).

About the study: 34 patients with a mean age of 72 years were enrolled between June 2006 and April 2007 in three centers. Patients presented with predominantly classic, minimally classic, or occult (with no classic) choroidal neovascularization (CNV). Depending on which treatment group they were in, patients received:

• One injection of Avastin prior to treatment, plus one application of 24 Gy epimacular beta radiation and one additional injection at the time of treatment
• One application of 24 Gy epimacular beta radiation and one injection of Avastin at the time of treatment, plus one additional injection after one month

Sustained response over time: 25 patients have now been followed for 18 months, and their visual acuity tested regularly using the ETDRS eye test (see sidebar for more information). After 18 months:

• 44% of patients gained 15 or more letters
• 8% gained 30 or more letters
• Mean improvement was 10.7 letters
• 96% of patients lost 15 or fewer letters

Although Avastin was available for administration as needed at any time during follow-up, only 7 patients needed 1 additional injection, and 1 patient needed 2 additional injections.

Demonstrated safety: Most of the limited number of adverse events were related to the vitrectomy procedure, rather than to radiation delivery. The most frequent adverse event associated with the procedure was cataract formation, with 25% of subjects phakic at baseline developing a cataract.

 

Event	Frequency
Cataract (>2 LOCS II grade increase from baseline)	25.0% (6/24)*
Subretinal fibrosis	5.8% (2/34)
Epimacular membrane	2.9% (1/34)
Retinal tear	2.9% (1/34)
Subretinal hemorrhage	2.9% (1/34)

*Calculated from phakic patients at baseline visit.

This ongoing study has provided valuable information about the long-term effects of beta radiation therapy. This study and other feasibility study data provided a strong rationale to pursue a Phase III pivotal study of NeoVista technology.

Click here to learn about the CABERNET Phase III study.