Re: [R] OT Futility Analysis

From: Spencer Graves <spencer.graves_at_pdf.com>
Date: Wed 22 Feb 2006 - 14:44:39 EST

          What does this particular Steering Committee think a "futility analysis" is? Do they have any particular reference(s)? What do you find in your own literature review?

          If it were my problem, I think I'd start with questions like that. Your comments suggested to me a confounding of technical and political problems. The politics suggests the language you need to use in your response. Beyond that, I've never heard before of a "futility analysis", but I think I could do one by just trying to be clear about the options the Steering Committee might consider plausible and then comparing them with appropriate simulations -- summarized as confidence intervals, as you suggest.

          And I hope that someone else will enlighten us both if there are better options available.

	  Best Wishes,
	  spencer graves

p.s. For any attorneys who may read these comments, the suggestions are obviously warranteed up to the amount you paid for it, which is nothing.   If you follow them and they turn out to be inappropriate, you will pay the price. I encourage you to share the problems with me, so I can learn from the experience. However, the limits of my liability are as already stated.

Kevin E. Thorpe wrote:

> I beg your pardon if this is too off topic. I am posting here
> since I hope to find an R solution to my problem. Please indulge
> me while I give a little background about what I'm trying to do.
>
> I'm on a DSMB for a clinical trial. The Steering Committee for the
> trial has asked us to perform a futility analysis on their primary
> outcome which is a time-to-event endpoint. The trial was not designed
> with group sequential methods, nor was any futility analysis spelled
> out in the protocol. Another thing which may be relevant is that
> due to circumstances beyond the investigators' control, the trial
> will stop recruitment prematurely unless there is some compelling
> reason for them to find a way to continue the trial. Lastly, the
> trial has accrued not quite half of the planned sample size.
>
> Admittedly, I don't have a vast amount of experience implementing
> stopping rules. In other protocols I have seen where futility
> analyses have been planned but a group sequential design has not
> otherwise been employed, conditional power has been used for the
> futility rule. So naturally, that was my first thought (although
> I may well be wrong) in this case. I have done RSiteSearch() with
> the following terms (three different searches):
>
> futility analysis
> conditional power
> stochastic curtailment
>
> Nothing that looked relevant to my problem jumped out at me.
>
> I have read, somewhat recently, that there are problems with conditional
> power, although I don't remember the details at the moment. This
> has prompted me to consider other approaches to the problem.
>
> One simple thing that has occurred to me, although I don't know
> what the implications are is to simply look at a confidence
> interval around the hazard ratio for the treatment effect. In
> the event that the CI includes 1 and excludes any clinically
> important difference, I would take that as an indication of
> futility.
>
> I would appreciate your comments on this and to learn of any more
> formal methods, particularly of implementations in R.
>
> Thank you for reading.
>
> Kevin
>



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