VITRASERT: NEWLY APPROVED GANCICLOVIR IMPLANT FOR CMV RETINITIS
Vitreoretinal News for the Medical Community
Vitrasert efficacy is quite dramatic. The time to progression of untreated retinitis is 15 days vs 226 days in the treatment group.
Cytomegalovirus (CMV) retinitis was the topic of our last newsletter. Until recently the only FDA approved treatments were intravenous ganciclovir and foscarnet. Their use required indwelling intravenous catheters. In patients incapable of intravenous therapy the use of intravitreal injections salvaged certain eyes. Unfortunately, the injections are required once or twice weekly. Oral ganciclovir has been demonstrated to stabilize regressed retinitis but only after intravenous induction therapy.
Vitrasert is an intraocular sustained-release ganciclovir implant recently approved by the FDA for use in the treatment of CMV retinitis in patients with AIDS. The implant is composed of a core of ganciclovir covered by ethylene vinyl acetate on all but its top surface. The whole assembly is coated with polyvinyl alcohol. The device delivers 1µg/h of ganciclovir into the vitreous cavity and has a theoretical lifespan of 8 months. The implant can either be exchanged or a second or third one implanted into the same eye.
The surgical procedure is quite straightforward. A 5.5 mm scleral incision is made at the pars plana. Any prolapsed vitreous is removed with the vitrector and the Vitrasert is anchored to the sclera and the sclerotomy closed with nonabsorbable suture. The total surgical time is approximately forty-five minutes and is performed under local anesthesia as an out-patient. The procedure is currently available at Providence and Richland Memorial hospitals. It is a covered service by most insurance companies as well as Medicaid and Medicare. The device is quite expensive. The cost to the hospital is $4000.
The efficacy of the Vitrasert implant is quite dramatic. Without any form of treatment the time to progression of retinitis is 15 days vs 226 days in the treatment group. In patients treated with intravenous ganciclovir or intravenous foscarnet the time to progression is 47 days and 53 days, respectively. Nearly 90% of those with peripheral disease retained 20/25 vision.
Complications of Vitrasert implantation are few. Retinal detachment occurs in 18% and no eyes in the multicenter study developed endophthalmitis. Most eyes will have a transient decrease in vision due to astigmatism or rapidly clearing vitreous hemorrhage.
Patients treated with the ganciclovir implant alone may develop cytomegalovirus in other end organs. Nearly 50% of patients will develop CMV retinitis in the contralateral eye by 6 months. Visceral disease may occur in 31% and pulmonary disease in up to 76%. Survival for patients treated with the Vitrasert implantation is approximately 9.8 months compared with 8.5 months for intravenous ganciclovir and 12.6 months with intravenous foscarnet. Co-therapy with oral ganciclovir, or even intravenous cidofovir (Vistide) given every two weeks may reduce the incidence of contralateral CMV retinitis and systemic CMV disease.
Intravitreal cidofovir given as a 20µg dose may stabilize CMV retinitis for approximately 6 weeks. It has a narrow margin of safety and is currently investigational.
