Eyeworld

EW GLAUCOMA 34 by Maxine Lipner Senior EyeWorld Senior Contributing Editor Prostaglandins under pressure: medications perform equally for all Race not found to factor into outcome A ll three prostaglandin in- hibitors, latanoprost (Xalatan, Pfizer, New York), travoprost (Tra- vatan, Alcon, Fort Worth, Texas), and bimatoprost (Lumigan, Allergan, Irvine, Calif.) are equally safe and effective at lowering pres- sure among members of different racial groups, according to Cather- ine M. Birt, M.D., associate profes- sor, department of ophthalmology and vision sciences, University of Toronto, Toronto. In the September 2010 issue of the Journal of Glau- coma, investigators reported on a trial dubbed the "Pressure study," which evaluated how the three prostaglandin inhibitors compara- tively fared among those with differ- ent ethnic backgrounds. The study was spurred by an earlier investigation, conducted by J.T. Whitson, that had delved into travoprost use. In the study, which was published in Expert Opinion on Pharmacology in July 2002, investiga- tors found that travoprost was par- ticularly effective at IOP reduction and diurnal control among African- American patients. "There was a suggestion as a post-hoc sub-analysis of a previous comparative study that one of the three [travoprost] worked better in the black population than in the white population," Dr. Birt said. "If true, this would have some impact on how we prescribe." Toronto-based study To see if these earlier findings would be proven true again, investigators, under the auspices of the Toronto- area glaucoma society, performed a prospective, randomized study on newly diagnosed open-angle glau- coma patients. "We wanted to see if we could replicate the study in a prospective fashion," Dr. Birt said. "We thought that since we have a very multicultural population in Toronto we could look at several dif- ferent ethnic groups and see whether there was anything that truly stood out." Included in the study were 83 patients recruited from nine sites. All were either newly diagnosed with primary glaucoma, pseudoexfo- liation, or pigmentary disease or had pressure that was amenable to being placed on one of the three prostaglandin inhibitors following a washout period. "It was a prospec- tive, randomized allocation of new patients, newly diagnosed patients, or those who were suitable to be washed off of their therapy and re- assessed without treatment," Dr. Birt said. "Mostly they were newly diag- nosed and were put on one of the three prostaglandin drugs randomly according to an allocation that our statistician set up so that it was bal- anced for drug and ethnic group." All patients had to be suitable for monotherapy. "I don't believe that any patient failed in the first six months," Dr. Birt said. "Everyone was treated quite effectively for the six months that they were in the protocol." Patients included in the study were divided into two groups, white and other. At the six-month mark, investigators found that all of the patients in the two groups fared comparably on the three prostaglandin drugs, with a high sta- tistical decrease in IOP in all groups. "We found that there was a sig- nificant improvement in pressure control in all patients, but there weren't any significant differences that could be attributed to ethnic- ity," Dr. Birt said. "All the drugs worked, but we didn't find that there was any interaction between ethnic group and drugs as had been suggested by the previous study." Study design analysis The earlier study results may be at- tributable to the study design, Dr. Birt thinks. "There is always a dan- ger when you're doing a retrospec- tive reanalysis of the data that the original study was designed to ques- tion," she said. Dr. Birt acknowl- edged that there were flaws in their study. "Our study unfortunately did not reach its sample size require- ments as determined by the power calculations," Dr. Birt said. "It's pos- sible that the effect is truly there but that we were underpowered to de- tect it—we recruited 83 patients but originally we were hoping for closer to 200." Dr. Birt hopes that practitioners come away from the recent study with the understanding that all three prostaglandin drugs are effec- tive treatment options for all open- angle glaucoma patients and not dependent on race. "All three of the prostaglandin drugs work well, and we do not feel that there is any need to select among the three based upon the patient's ethnicity," she said. "We didn't find that any one showed statistically significant supe- rior pressure lowering, whether or not ethnicity was factored in." Going forward, Dr. Birt recom- mended that any future study on this should include an international component. "I would personally suggest that if anyone wanted to try this study again, it might have to be international rather than recruiting from a single city," she said. "The in- vestigator could go to parts of the world where there is a much higher proportion of Hispanics, African- Americans, and Chinese-Asians and get good numbers." EW Editors' note: Dr. Birt has financial in- terests with Alcon (Fort Worth, Texas), Allergan (Irvine, Calif.), and Pfizer (New York). Contact information Birt: 416-480-6053, catherine.birt@sunnybrook.ca Glaucomatous optic nerve; prostaglandins and beta blockers are used to treat lower pressure in ocular blood vessels Source: Douglas J. Rhee, M.D. " We found that there was a signifi- cant improvement in pressure control in all patients, but there weren't any signifi- cant differences that could be attributed to ethnicity "

• Cover