Clark has suggested some modelling in earlier posts I am catching up on, but I do not know how accurate these are and how much they rely on a priori assumptions that may not hold true.
You are completely correct that the assumptions, and their effects, are the interesting part:
a) I assumed standard exponential survival curves, which have the same instantaneous HR at any point in time - when in fact the 9901/2a curve says that the HR increases substantially over time. Don't know what effect this difference will have.
b) I assumed constant enrollment curves, instead of the back end loaded curves that we will inevitably have.
c) I assumed a TRUE HR of 1.40. Who knows what it is in this population?
...
All in all there is a lot of noise. All you can do is get a rough idea of the playing field.
Clark
