A case report of data monitoring experience: the nocturnal oxygen therapy trial

The monitoring of accumulating data in a clinical trial is a challenging endeavor, yet one that must be undertaken to fulfill the ethical responsibility to the participating subject. This paper, using the Nocturnal Oxygen Therapy Trial as an example, discusses three issues often faced by data monitoring committees. These are (1) the multiplicity of outcomes, (2) decisions about extension of the patient recruitment period in order to achieve specified sample size goals, and (3) problems in monitoring survival data with a lag in the reporting of events. The decision process can be quite complex and existing statistical methodology can at best serve as a guide in this decision process.