Abstract
Background: The classical two-period crossover and two-parallel-groups designs for clinical drug trials are unable to answer many current scientific questions, and are sometimes ethically or financially impossible.
Objectives: To identify what a classical clinical trial cannot manage, to summarize and discuss alternative trial designs that are helpful for such purposes.
Results: What a classical clinical txkI cannot manage
assess multimodal therapies
account historical data
safeguard ethics and efficacy during the course of long-term trials
study drugs, before well-established toxicity information is available
account the possibility of therapeutic equivalence between test and reference treatment
study multiple treatments in one trial
adjust change scores for baseline levels.
Alternative designs helpful for such purposes are respectively
factorial designs
historical controls designs
group-sequential interim analysis designs
sequential designs for continuous monitoring
therapeutic equivalence designs
multiple crossover-periods / multiple parallel-groups design
increased precision designs through multivariate adjustment.
Main problems include the increased risks of type I/II errors, the loss of validity criteria.
Conclusions: Non-classical trial designs are reviewed. They offer relevant scientific, ethical, and financial advantages. The increased risks of type MI errors should be accounted for in the design stage of the trial.