Sample Size and Power: Phase 3 Trial Examples Part 4

So, we can go a little bit through this Phase III example. And here, this is actually a survival example. So, our primary objective here was to determine if patients with metastatic melanoma, who underwent this procedure had a different overall survival compared with patients receiving standard of care. So, remember, we have to then define standard of care.

But they were trying to do all this and the idea was that we're going to have a two-arm randomized Phase III single institution trial. We don't see many Phase III trials done at one site, but this one was going to be. So, they came to us and said, "How many patients do we need to enroll?" We want to have a 1-to-1 ratio between the arms.

So, we're going to equally randomize to the two study arms. We want 80 percent power to detect a difference between eight-month median survival and 16-month median survival. Again, then you need to look and say, "Okay, what's currently on the market? What's going on? Do these values still make sense?" They added two-tailed 0.05 test they wanted to run.

And they wanted to do 24 months of follow-up after the last patient had been enrolled. And they were planning on doing 36 months of accrual. These lovely things are called nomograms. So, I have plenty of books with lots of formulas. And I have to say, actually, of all sample size calculations, probably I like survival analysis ones the most

because you get to move a lot of different things. But some of the best statisticians I work with keep photocopying this picture. There's this paper that basically has different figures and the number of patients per treatment group. So, you set -- they have different pictures for alpha and beta combinations. The dashed lines are for two-sided tests and the solid lines are for one-sided tests.