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I need to calculate the AUC for a Cox regression model. SAS is giving me a time dependent AUC as below. How do I report this for the paper?

Thanks!! enter image description here

ybao
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    There is no single AUC for a Cox model. Because, for any given time, a patient on study may not have had the event yet. – AdamO Mar 24 '22 at 18:26
  • @AdamO How do I go about reporting this? Do I report the time dependent AUC at specific time points? – ybao Mar 25 '22 at 02:41
  • an AUC has to do with a prediction, and I don't understand how you'd be interested in a prediction measure if you don't know the time point you're interested in reporting. The problem with SAS is that gives you absolutely every f***ing statistic in the world, but only 2% of that matters, usually just the coefficients., – AdamO Mar 25 '22 at 17:09

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What's routinely done with Cox survival models is to report the concordance or C-index. That's the fraction of comparable cases for which the predicted and observed order of event times agrees. In a binary regression model that type of index would be the AUC. See this page for example. It's possible that, in an abuse of terminology, someone asked you for AUC when the request was intended to be for a C-index.

For the time-dependent AUC you could simply show the plot itself if there's space, or report selected time points in the text and put the plot into supplemental material. It would be important also to show confidence intervals around the AUC estimates. Do make sure that you understand which method has been used to calculate the time-dependent AUC, as there are several.

EdM
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