Monthly treatments with ranibizumab in patients with neovascular age-related macular degeneration could reduce the incidence of legal blindness and vision impairment by 72% and 37%, respectively, in 2 years, according to a study in the June 2011 issue of Archives of Ophthlamology.
Before ranibizumab (Lucentis) became available in 2006, neovascular age-related macular degeneration (AMD) was considered to be the leading cause of blindness in individuals aged 50 and older in the United States, with its prevalence estimated to be 1.6 million cases by 2050. Studies have shown that monthly injections of ranibizumab, a vascular endothelial growth factor (VEGF) inhibitor, not only reduce the risk of substantial vision loss, but may lead substantial improvement in visual acuity.
With this in mind, Dr. Neil M. Bressler of the Wilmer Eye Institute at Johns Hopkins University in Baltimore and his colleagues attempted to estimate how many individuals in the United States who have neovascular AMD might avoid legal blindness or visual impairment (defined as a best-corrected visual acuity of 20/40 or less in both eyes) by receiving monthly injections of ranibizumab (Arch. Ophthalmol. 2011;129:709-17).
In research sponsored by Genentech, Dr. Bressler’s team designed a computer modeling study that estimated the incidence of neovascular AMD among non-Hispanic whites, as well as the number of patients in whom ranibizumab would be indicated and accessible, and the anticipated visual acuity outcomes. The researchers did not include racial subgroups because there is limited information regarding the incidence of choroidal neovascularization (CNV) in other populations.
First, the authors multiplied estimates of the population of non-Hispanic whites older than 50 years in the United States, based on 2008 data from the U.S. Census Bureau, and then multiplied that number by the incidence of neovascular AMD in the Beaver Dam Eye Study. The Beaver Dam Eye Study estimated a 15-year cumulative incidence of AMD.
The researchers also classified lesion characteristics and based anticipated visual acuity outcomes on three studies: AREDS (Age-Related Eye Disease Study) Report No. 11, the ANCHOR (Antivascular Endothelial Growth Factor Antibody for the Treatment of Predominantly Classic Choroidal Neovascularization in Age-Related Macular Degeneration) study, and the MARINA (Minimally Classic/Occult Trial of the Anti-VEGF Antibody Ranibizumab in the Treatment of Neovascular Age-Related Macular Degeneration).
The model predicted that 151,340 non-Hispanic white individuals in 2008 would develop neovascular AMD. Based on data from AREDS, ANCHOR, and MARINA, the model predicted that 51,000 (33.7%) of these individuals who already had AMD in one eye also already had CNV in the opposite eye, making them ineligible for the model used in this study. The researchers also estimated that 103,582 individuals (68.4%) in whom monthly ranibizumab was indicated would have access to ranibizumab, making them eligible for inclusion in the study’s modeling criteria.
According to the model, if none of these eligible individuals received treatment, 16,268 (15.7%) would become legally blind in 2 years, and another 34,702 (33.5%) would become visually impaired. If all these individuals received monthly injections, however, 4,484 individuals (4.3%) would become legally blind, and 21,919 individuals would become visually impaired. This represents a 72% and 37% reduction in the incidence of legal blindness and visual impairment, respectively.
The researchers did report limitations in the study. "This model has several assumptions and weaknesses that require one to interpret the numbers put forth in this study as only an approximation," the researchers said.
For example, the incidence rates of CNV were based only on the Beaver Dam Eye Study, the model did not consider other racial subgroups, the estimates in this model assumed measurement of best-corrected visual acuity on high-contrast charts, and the results assumed access to monthly ranibizumab for 2 years, even though many clinicians discontinue treatment before then.
Still, the authors believe that monthly ranibizumab, when indicated and accessible, would dramatically reduce the cases of legal blindness resulting from neovascular AMD in individuals aged 50 years and older.
Genentech funded the study and participated in the design and conduct of the study; in the distribution of the raw data; in the analysis and interpretation of the data; in the preparation of the manuscript, and in review of the manuscript before submission. Several of the coauthors are consultants for Genentech.