This is perhaps the most common type of situation in which even quite small alterations to the allocation ratio can make participation in the trial much easier, the resulting increase in accrual more than compensating for the slight loss in power associated with moving the allocation ratio away from equality. One example involved the trials of continuous, hyperfractionated accelerated radiotherapy (CHART) in head and neck, and also lung cancer described earlier in this chapter . As CHART is given in multiple daily fractions, without breaks for weekends, patients are treated outside of normal hours and this therefore incurs additional staff costs. It is clearly more cost effective to have several patients ready to treat in succession. In the MRC CHART trials, 3 : 2 randomization was used to increase the number of patients allocated CHART, and therefore increase the chance that participating centres would have several patients to treat simultaneously.
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