a card game, as poker, in which the dealer decides what particular game is to be played, often depending on the number of players, and designates any special variations or unusual rules, including setting the stakes."
In contrary to the randomized clinical trial, an approach called "dealer's choice" has now been used in clinical trials or in clinical setting (more often in oncology clinical trials) where the treating physician decides which treatment regimen will be given to the patients/subjects. Typically, this happens when there are several treatment regimens, but there is no sufficient information to decide one is better than others.
While this is ok for treating the patients in clinical setting, it is not ideal when this approach is used in clinical trial. # of subjects who receive on specific treatment regimen will depend on the dealer's choice and may be imbalanced in terms of the sample size and the subject characteristics across different regimens. At the end of the study, if there is any difference among treatment regimens, there may be due to the 'unknown' confounding factor rather than the treatment itself.
Here are some of the examples using "dealer's approach":
An intergroup rectal cancer trial supported by NCI employed the dealer's choice approach in which treatment would be chosen by the physician and patient together.
Interventional Management of Stroke (IMS) III Trial (IMSIII) did not explicitly use the term "dealer's approach". However, in the investigational treatment arm, after initial tPA treatment fails, the doctor will choose--based on the location and extent of the blood clot--one of 4 possible IA treatments given directly in the brain artery that will be most effective in reopening the blocked artery. There is no randomization. It is dealer's choice in choosing one of the four treatment options.
There may be legitimate reason in using "dealer's choice" approach, it certainly compromise the quality of the trial and make the interpretation of the results more difficult.