Megatrials are based on a methodological mistake.

Despite their prestige, megatrials are founded upon a methodological error. This is the assumption that randomization of very large numbers of subjects can compensate for deliberately reduced levels of experimental control, but there is no trade-off between size and rigour. Randomized trials are not a 'gold standard' because no method is intrinsically valid-there are good and bad trials. Interpretation of megatrials is always difficult and requires considerable clinical and scientific knowledge. Three fundamental parameters should be considered when evaluating the applicability of a trial to clinical practice: rigour of design; representativeness of the trial population; and homogeneity of the recruited subjects.