Maximal Extension Interval and Visual Outcomes in a Treat-and-Extend Protocol: A Post Hoc Analysis of the CANTREAT Randomized Trial

Abstract

Introduction: The Canadian Treat-and-Extend Analysis Trial with Ranibizumab (CANTREAT) was a 2-year, multicentred, randomized clinical trial to evaluate treat-and-extend (T&E) relative to monthly administration of ranibizumab in neovascular age-related macular degeneration (nAMD). This post hoc analysis of the CANTREAT trial explores the relationship between the maximal extension interval tolerated by patients receiving T&E ranibizumab and visual acuity outcomes. Methods: Treatment-naïve patients with nAMD were randomized to receive either a once-monthly dosing or T&E regimen of ranibizumab across 27 treatment centres in Canada and were followed for 24 months. For this post hoc analysis, patients in the T&E cohort were subdivided into the following groups based on maximum extension interval: 4 weeks, 6 weeks, 8 weeks, 10 weeks, and 12 weeks. The primary outcome was the change in ETDRS best-corrected visual acuity (BCVA) from baseline to month 24 while secondary outcomes included change in central retinal thickness (CRT). All results were reported using descriptive statistics. Results: A total of 285 participants undergoing T&E were enrolled in this post hoc analysis. At month 24, the change in BCVA from baseline was +8.5 ± 9.3, +7.7 ± 13.8, +4.4 ± 9.6, +4.4 ± 18.5, and +7.8 ± 14.8 letters in the 4-, 6-, 8-, 10-, and 12-week cohorts, respectively. The change in CRT at month 24 was −79.2 ± 95.0, −143.9 ± 128.9, −97.7 ± 101.1, −120.9 ± 105.3, and −133.2 ± 108.8 μm in the 4-, 6-, 8-, 10-, and 12-week cohorts, respectively. Conclusion: The capacity to extend does not necessarily associate with improved visual acuity outcomes, with the poorest change in BCVA seen in those extended 8–10 weeks. The highest change in BCVA and lowest decrease in CRT was in the group maximally extended for 4 weeks. There was a correlation between change in BCVA and change in CRT for other extension groups. Future studies should establish the predictive factors for successful extension in patients undergoing T&E in nAMD.