Conclusion
To conclude, RCTs with a no-treatment arm, low funding, low financial compensation per included patient are more likely to experience recruitment failure, while a preceding pilot study lowers this chance. We propose that investigators and grant providers consider these issues before the actual start of the study, to improve the chances of recruitment success. If a relevant trial is destined to have a suspected long recruitment period, it seems wise to ponder on the question whether to start the trial, or to accept a longer recruitment period with all its consequences.