on a related note do you think the FDA/community's working definition of futility is changing? I mean it made sense to give a futility rec at an IA in the old days of chemotherapy when you're just expecting to shift the KM curve to the right - if it hasn't shifted sufficiently by the IA it's very unlikely to result in a stat sig HR by the end of the trial. But these days with immunotherapies and the long (fat is a better word) tail you can still easily end up with a stat sig HR at the end of the trial even if there is no or little distinction between the arms at the IA.
Yes, I acknowledged that at the bottom of this post here. See my thoughts about Futility, “Long tails”, and immunotherapies (echoing Hoos and Berry).
All the more reason why a futility stop may have been recommended but not disclosed.