Substituting a randomised placebo control group with a historical placebo control in an endometriosis pain trial: a case study re-evaluating trial data using historical control data from another trial.

Objective: The substitution of an in-study control population with a historical control (HC) population is considered a viable option for reducing the necessary recruitment of control patients. However, it is necessary to evaluate whether this method is applicable to studies on indications targeting endometriosis-associated pelvic pain (EAPP). This study aims to evaluate the potential bias in the results of an EAPP study with an HC arm.