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Cytomegalovirus retinitis is an infection associated with the acquired immunodeficiency syndrome (AIDS) that, if left untreated, causes progressive retinal destruction with partial or complete visual loss. Retinitis develops in up to 40 percent of patients with AIDS.1-6 Intravenous formulations of two agents, ganciclovir (Cytovene-IV) and foscarnet (Foscavir), are approved in the United States for the treatment of cytomegalovirus retinitis. Lifelong maintenance treatment can slow the progression of retinitis and minimize vision loss.7-14 Daily intravenous therapy is associated with substantial cost, inconvenience, and risk of catheter-related complications. An effective oral treatment would be an important advance.A capsule form of ganciclovir (Cytovene) for oral administration has been studied. The absolute bioavailability of ganciclovir administered orally in a dosage of 1000 mg three times daily with food averaged 9 percent.15 Daily doses of 3000 mg or more yielded average serum ganciclovir concentrations exceeding 0.5 μg per milliliter,16 a concentration sufficient to inhibit most clinical isolates of cytomegalovirus in vitro.17 Oral ganciclovir also reduced viral shedding and viral titers in urine and semen. Oral ganciclovir was tolerated at doses of up to 6000 mg daily; the rate of neutropenia was higher at doses of 6000 mg daily.16We compared the efficacy and safety of oral ganciclovir at a daily dose of 3000 mg with that of intravenous ganciclovir at a daily dose of 5 mg per kilogram of body weight as maintenance therapy for cytomegalovirus retinitis. The disease was first stabilized with intravenous ganciclovir.METHODSSubjectsAfter approval by the institutional review boards, the study was conducted at 15 centers in the United States and Canada. Eligible subjects were at least 13 years of age, had been given a diagnosis of AIDS, and had been given a diagnosis of cytomegalovirus retinitis of one or both eyes within one month before entry. No exclusions were made on the basis of the location or extent of retinitis. Patients who had signs and symptoms of serious gastrointestinal disease, an absolute neutrophil count below 1000 cells per cubic millimeter, a platelet count below 50,000 per cubic millimeter, or a creatinine clearance rate of less than 70 ml per minute were ineligible.Randomization and TreatmentAfter providing informed consent, enrolled subjects received 21 days of induction therapy with intravenous ganciclovir at a dose of 5 mg per kilogram twice daily for 14 days, followed by a dose of 5 mg per kilogram once daily for 7 days. All subjects whose retinitis stabilized (defined as no progression on two consecutive ophthalmologic evaluations on weeks 2 and 3 after the start of induction therapy) were randomly assigned (on a 1:1 basis) to open-label maintenance treatment with either intravenous ganciclovir (5 mg per kilogram once daily) or oral ganciclovir (500 mg six times daily during waking hours; total, 3000 mg per day), taken with food.The subjects were followed for up to 20 weeks after the start of maintenance therapy. If retinitis was judged by experienced ophthalmologists to have progressed, the subjects received a second course of induction therapy with intravenous ganciclovir. If retinitis again stabilized, the originally assigned maintenance treatment was resumed. Subjects in whom retinitis progressed a second time were withdrawn from the study.Clinical and Ophthalmologic EvaluationsThe subjects were evaluated every two weeks after starting maintenance treatment, and a limited history was taken to collect data regarding adverse events, concomitant medications, and AIDS-related clinical events. Hematologic and serum chemical tests were performed every two weeks; CD4+ lymphocyte counts were made at the start of maintenance therapy and on weeks 4 and 20.Urine cultures for cytomegalovirus were scheduled at entry, at the start of maintenance therapy, and on week 20 or in the event of early withdrawal from the study, progression of retinitis, or the development of extraocular cytomegalovirus disease. Other cultures (e.g., of blood or semen) were encouraged, and if they were done, the results were included in the analysis. Isolates from positive cultures were tested for susceptibility to ganciclovir in diploid-fibroblast cultures with a plaque-reduction assay.18 Resistance was defined as a 50 percent inhibitory concentration in excess of 2.9 μg per milliliter or a 90 percent inhibitory concentration in excess of 7.4 μg per milliliter.19Ophthalmologic evaluations were conducted every two weeks and were the basis for treatment decisions. Best corrected visual acuity on Snellen's test was determined, and the subjects were asked to assess their functional vision using the following scale: 1, able to read newspaper print; 2, able to identify people and objects; 3, able to distinguish light from dark; and 4, unable to see anything. Ophthalmologists performed an indirect ophthalmoscopic examination of the fundi in patients' dilated eyes (funduscopy). Progression of retinitis was defined as advancement of the border of a lesion by at least 750 μm (approximately half the optic-disk diameter) or the appearance of a new lesion of at least 750 μm in a previously uninvolved area of either fundus.Photographs of the fundi were taken every two weeks. At most centers, a wide-angle camera (50 or 60 degrees) was used. Photographs included all of zone 1 of each eye (the area within 1500 μm of the edge of the optic disk and within 3000 μm of the fovea), whether or not the eye was affected by retinitis. Additional photographs were taken to document the location and extent of all lesions noted on funduscopy. At the completion of the study, all photographs were evaluated by a single grader, who was unaware of the patients' treatment assignments. Photographs taken closest to the date of randomization served as the base line. The definition of progression on the basis of photographic assessment was identical to that for funduscopy.Efficacy End PointsThe primary efficacy end point was the length of time from the start of maintenance therapy to the progression of retinitis. Other specific ophthalmologic outcomes included the proportions of subjects in whom existing lesions increased in size by at least 750 μm, new lesions developed in either eye, retinitis extended into zone 1, active lesion borders developed, retinal detachment developed, and changes in visual acuity or functional vision were recorded. Other secondary end points were survival, the development of extraocular cytomegalovirus disease, the occurrence of other AIDS-associated infections and malignant conditions, changes in the counts of CD4+ lymphocyte subgroups, the occurrence of positive cultures for cytomegalovirus, and the development of ganciclovir-resistant strains of cytomegalovirus.Safety End Points
Adverse events were monitored throughout ganciclovir treatment with the use of history taking, physical examinations, and laboratory tests.
Statistical Analysis
The mean time from the start of maintenance therapy to the progression of retinitis was the primary end-point measure. On the basis of clinical experience, the mean time to the progression of retinitis during maintenance therapy with intravenous ganciclovir was expected to be approximately 70 days. A sample of 120 subjects was considered sufficient to give the study 80 percent power to detect a difference of 25 days or more in the mean time to progression between treatment groups with use of a two-sided test at the 0.05 level.
The time to the progression of retinitis was compared in the two groups by Kaplan–Meier curves and the log-rank test and analyzed with a proportional-hazards regression model. The relative risk of progression was expressed as the ratio of the rate of progression during oral ganciclovir maintenance therapy to that during intravenous ganciclovir maintenance therapy; a relative risk greater than 1 indicated an increased risk of progression with oral maintenance therapy.
The proportions of subjects in each group with deterioration of visual acuity and functional vision, extension of retinitis into zone 1, increase in the size of existing lesions, new lesions, development of active lesion borders, and development of retinal detachment were compared with Fisher's exact test. The time to the deterioration of visual acuity was analyzed by Kaplan–Meier curves and the log-rank test. Three broad categories of visual acuity were defined: 20/40 or better, 20/50 to 20/100, or 20/200 or worse. Deterioration of visual acuity was defined as a change from one category to a worse category for either eye on two consecutive visits or on the last visit during the study.
Adverse events specifically reported as related to intravenous catheters or infusion sites were categorized as catheter-related adverse events.
To determine the survival rate, all subjects, including those who withdrew early from the study, were followed until October 25, 1994. Survival was assessed according to randomized treatment assignment (intention to treat), and the results were compared with Kaplan–Meier curves and the log-rank test.
RESULTS
A total of 161 subjects were enrolled between March 1991 and June 1992. Thirty-eight subjects were not randomly assigned to maintenance treatment for the following reasons: unstable retinitis after the three weeks of induction therapy (n = 18), abnormal laboratory results (n=11), a decision by the subject not to participate (n = 4), administrative problems (n = 3), or death (n = 2). Thus, 123 subjects were randomly assigned to receive maintenance treatment with intravenous ganciclovir (n = 60) or oral ganciclovir (n = 63). Six subjects were excluded from the efficacy analyses: two did not receive maintenance treatment, two received laser photocoagulation treatment that made it impossible to evaluate whether retinitis had progressed, and two had been given
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