Triangular test and randomized trials: practical problems in a small cell lung cancer trial.

The triangular test has been used to monitor survival data from a randomized trial in patients with small cell lung cancer. The results of consecutive interim analyses and the problems met by the data monitoring committee and the co-ordinators are described. The methods as well as the consequences of the early stopping on the analysis and the results of this trial are discussed. From this experience, we believe that statistical stopping rules--only one of the factors to be taken into account when deciding to stop a trial--should be used with caution. Independent data monitoring committees may be useful in helping to review the ongoing results and advise the participants in the trial.