If two independent trials are conducted, cross contamination is eliminated though it maybe necessary to provide guidelines concerning duration of chemotherapy in each of the three arms of the first trial. However, the trials will take longer than if the questions were combined in a single trial and, on a practical note, data collection is increased.
The option chosen for CR06 was option 1, having performed sensitivity analyses. These assumed a 10% difference in survival for stop versus continue in those patients whose disease had not progressed at three months, and showed that even for unrealistically extreme differences in the proportion of patients achieving a response (or agreeing to be randomized) at three months across the three chemotherapy arms, the estimated differences in survival between any two of the three chemotherapy arms would be increased or decreased by less than 1%. Some of the calculations are detailed in Box 4.5. Similar orders of effect were found when allowing for a number of other scenarios including different long-term survival rates for patients with responding and stable versus progressive disease at three months, or for different response rates across the regimens. The conclusion was that the impact of the varying assumptions was minimal, and that this design was the most appropriate. However, both of the trial randomizations were kept
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