Box 45 Example of the type of calculations performed to aid the design of CR06

If the assumptions underlying the sample size calculations are met, then:

♦ 50% of patients (on any of the three regimens) will have stable or responding disease at twelve months (this was an equivalence trial)

♦ the 18-month survival rate of patients with progressive disease is 10%

♦ the 18-month survival rate of patients with stable or responding disease allocated 'stop' chemotherapy is also 10% (previous trials showed no difference in the long-term survival rate of patients who had stable/responding disease compared to those with progressive disease at three months)

♦ the 18-month survival rate of patients with stable or responding disease allocated 'continue' chemotherapy is 20%

Assuming all eligible patients proceed to the second randomization, of 300 patients on any arm:

♦ 150 will have progressive disease at twelve weeks, and 10% 18-month survival,

♦ seventy-five will be randomized to stop chemotherapy and will have 10% 18-month survival,

♦ seventy-five will be randomized to continue chemotherapy and will have 20% 18-month survival.

This gives an overall 18-month survival of 12.5%

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