Noninferiority Studies

The usual therapeutic study is designed to determine superiority: is arm A or B more effective?
In some cases, we aim only to prove equivalence, not superiority. This can be if a new treatment is:
- More patient-friendly
- Cheaper
- More easily available
- Less invasive
Non inferiority trials are used when a new treatment has an advantage, asides from possible treatment efficacy, over the current standard treatment so one might accept a small decrease in the efficacy of the newer treatment because of this advantage.
Reasons for Choosing a Non-Inferiority Design
- Showing non-inferiority of the experimental treatment E versus the control treatment C can be of interest because of the following:
  - It is not ethically possible (anymore) to do a placebo-controlled trial.
  - Experimental treatment is not expected to be better than Control on a primary efficacy end point but is better on secondary end points or is safer.
  - Experimental treatment is not expected to be better than Control on a primary efficacy end point but is cheaper to produce or easier to administer.
  - Experimental treatment is not expected to be better than Control on a primary efficacy end point in a clinical trial, but compliance will be better outside the clinical trial and hence efficacy will be better outside the trial.