Terminating a long-term clinical trial.

Long-term trials often include more than one active treatment group. These may be discontinued independently if found ineffective or possibly harmful. Certain subgroups of patients may be discovered, in the course of a clinical trial, who do not respond satisfactorily and are, therefore, excluded during the course of a trial. Yet anouther kind of termination comes when we have a therapeutic breakthrough or when hope has to be abandoned for demonstrating beneficial effects for one, several, or all treatments included in a trial. Examples from the authors' experience are presented, as are successful and unsuccessful techniques in managing terminations of various types.