Switching therapy in health economics trials: confronting the confusion

Should patients in a randomized, pragmatic health economics trial be allowed to switch therapy in mid-trial to that provided in the other arm? Specifically, should patients in the treatment arm (T) be allowed to switch to the therapy of the comparator arm (C) if they need a change of therapy--that is, should TC switches be allowed? Also, should patients in the comparator arm be allowed to switch to the therapy of the treatment arm if they need changes of therapy--should CT switches be allowed? This is a nontrivial issue in study design that has been debated in the clinical trials literature and is currently being handled inconsistently in the health economics literature. In this article, the authors argue that TC switches should always be allowed and that CT switches should be allowed or not depending on the economic question. They further argue that the most common economic question is one that would lead to CT switches not being allowed.