[Generalizability of therapeutic trials].

The external validity of a therapeutic trial addresses whether the study results may be applicable to other patients beyond the original study population. The inclusion criteria of the original study are a good indicator of the extent to which new patients are comparable with the study population, based on key characteristics. If the patients included in the study are not representative of the target population, the external validity is limited. The external validity can also be limited by study aspects that are not related to the inclusion criteria, such as the treatment protocol, the treatment centre, or the country in which the original study was performed. In exceptional cases the external validity can involve patients that would have been excluded in the original study.