ABSTRACT
A multi-arm trial is one in which there are more than two treatment arms. There are many possible objectives of such a trial, including comparing multiple experimental treatment arms against a common control, and comparing an experimental treatment against several control groups (for example, a placebo and an active control). The main reason for using a multi-arm trial is that
it allows several primary research questions to be answered in a single trial with increased efficiency compared to separate trials. Multi-arm trials are increasingly of interest as for many diseases there are multiple treatments in the same phase of clinical development. For example, in oncology there are over 1500 cancer therapeutics in the clinical pipeline [23]. In addition to considering multiple distinct treatments, it may be of interest to evaluate several doses of the same treatment, several regimens of overlapping treatments, or several dose schedules of the same treatment. This may increase the potential number of treatment arms exponentially.
