Abstract: The intention to treat (ITT) principle is widely applied in the randomized controlled trials (RCTs), which is based on the intention to treat a subject (i.e. the planned treatment regimen) rather than the actual treatment given. With the development and progress of clinical trials, ITT principle needs to be reinterpreted. In the standard definition of ITT principle, the intentional grouping of subjects does not specifically refer to randomization, but rather to planned treatment regimen. In non-randomized clinical trials, that subjects agree to be included in a certain treatment regimen is also a type of intention. ITT principles can be applied to evaluate the effectiveness of treatment regimens under patient/doctor determined intentionality in single-arm clinical trials and non-randomized RWS (real world study, RWS). In the practical application, the grouping strategy based on ITT principle should be considered comprehensively according to the research purpose.

Key words: intended to treat, clinical trial, real world study, single-arm trial