Sometimes the goal of comparing a new treatment with a standard treatment is not to find an approach that is more effective but to find a therapy that has other advantages, such as lower cost, fewer adverse effects, or greater convenience with at least similar efficacy to the standard treatment. With other advantages, a treatment that is almost as effective as a standard treatment might be preferred in practice or for some patients. The purpose of a noninferiority trial is to rigorously evaluate a new treatment against an accepted and effective treatment with the goal of demonstrating that it is at least almost as good (ie, not inferior).
Kaji AH, Lewis RJ. Noninferiority TrialsIs a New Treatment Almost as Effective as Another?. JAMA. 2015;313(23):2371-2372. doi:10.1001/jama.2015.6645