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List:       r-help
Subject:    Re: [R] Comparing two different 'survival' events for the same subject using survdiff?
From:       Terry Therneau <therneau () mayo ! edu>
Date:       2013-04-30 14:55:19
Message-ID: 517FDB57.3030703 () mayo ! edu
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-----Original Message-----

I have a dataset which for the sake of simplicity has two endpoints. We wou=
ld like to test =

if two different end-points have the same eventual meaning. To try and take=
 an example =

that people might understand better:

Lets assume we had a group of subjects who all received a treatment. The co=
uld stop =

treatment for any reason (side effects, treatment stops working etc). Getti=
ng that data is =

very easy. Measuring if treatment stops working is very hard to capture... =
so we would =

like to test if duration on treatment (easy) is the same as time to treatme=
nt failure (hard).

--- End ----

The problem you describe is known as "surrogate endpoints" and addressing i=
t is harder =

than you think. You will need to look in the literature to gain an understa=
nding of the =

issues before you proceed. Your question is an important one and lots of fo=
lks have =

thought about it more deeply than I.

Cohn JN (2004). "Introduction to Surrogate Markers". Circulation (American =
Heart =

Association) 109 (25 Suppl 1): IV20=961. doi:10.1161/01.CIR.0000133441.0578=
0.1d

Fleming T, David D. Surrogate End Points in Clinical Trials: Are We Being M=
isled? Ann =

Intern Med. 1996 Oct 1;125(7):605-13

Terry T.

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