[Trials, observational research and the real world]. / Trials, observationeel onderzoek en de 'echte' wereld.

The treatment effect found in a randomized trial does not always correspond to the effect of the treatment in daily practice. To estimate the applicability of the results of a trial, a comparison can be made with the results of observational research. In this commentary we discuss such a comparison between the results of the TIME trial and the analysis of the observational DUCA database. Both compared open and minimally invasive oesophageal resection, yet results were strikingly different. We discuss nine possible explanations for the differences found in the effects of the two treatments.