Purpose: To present a new epidemiological method relying on randomized controlled clinical trial (RCT) data to assess whether a treatment was effective, aiding in the decision to continue or stop the treatment in clinical patients.
Methods: A cutoff point is calculated in the change of a continuous outcome for which a proportion of treated patients clearly achieved a change better than this cutoff point as a result of the treatment. This cutoff point can then be applied to individual patients during routine therapy. The method was applied to reports of the Minimally Classic/Occult Trial of the Anti-VEGF Antibody Ranibizumab in the Treatment of Neovascular AMD (MARINA) trial, which included patients with AMD treated with monthly intravitreal injections of ranibizumab, and to reports of trials involving patients with high IOP, macular edema, and convergence insufficiency.
Results: The cutoff point in the change in visual acuity (number of letters), above which a proportion of patients clearly benefited due to ranibizumab treatment, was -5.0 at 24 months follow-up. The proportion of treated patients who ended above this cutoff point due to the treatment was 60%. The cutoff point varies with time of follow-up and by subgroup.
Conclusions: Contrary to common interpretation, no change, or a limited decline, in the outcome (visual acuity) can still imply that the patients are better off with the treatment than with no treatment. Stopping the treatment above the cutoff point may not be appropriate since it was effective in at least a proportion of patients. This method applies to a broad range of scales and conditions. (ClinicalTrials.gov number, NCT00056836.).