st: HOW TO RETRIEVE TIME-SPECIFIC BASELINE AND PREDICTED SURVIVALFIGURES?

["Brian Harrison" <brianharrison@doctors.org.uk>]

Dear All,

I wonder if you could help me with the following query. I 
have been trying to retrieve time-specific baseline and 
predicted survival figures (and their 95%CI) after fitting 
a Cox model including a three-level categorical variable 
using the following commands:
stcox x2 x3 ,bases(BS)   (where x2 and x3 are dummy 
variables derived from x)
gen predx2=BS^exp(_b[x2]) if x2==1
gen predx2_L = BS^exp(-1.96*_se[x2]) if x2==1
gen predx2_U = BS^exp(1.96*_se[x3]) if x2==1
gen predx3=BS^exp(_b[x3]) if x3==1
gen predx3_L = BS^exp(-1.96*_se[x3]) if x3==1
gen predx3_U = BS^exp(1.96*_se[x3]) if x3==1

I have two difficulties here:
First, I do not know how I could retrieve the 95%CI 
estimates for the baseline survival.
Second, I do not know how to retrieve the baseline and 
predicted survival (and 90%CI) figures for specific 
survival times (e.g. 90 days, 1 year etc). In other words, 
is it possible to obtain a list of the time-specific 
baseline and predicted survival figures and their 95%CI in 
the same way the Kaplan-Meier survivor function could be 
retrieved for different survival times (using the command 
sts list,at(90,365))?

Many thanks for your help.

Brian Harrison


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