Thanks to Kit Baum, there is a new command named -stexpect- downloadable
from SSC. In Stata, use -findit- or -ssc- command to find out more.
stexpect computes expected survival probability after merging the data with
a suitable file of "standard" rates. You must specify in ratevar(varname) a
reference rate variable and in output(filename) a file where the estimates
will be saved.
The users familiar with Therneau's and Grambsch's book, Modeling Survival
Data Extending the Cox Model chap 10, will find implemented in this macro
some methods here described and at present available using survexp function
in R
Expected survival is used to produce an overall survival curve. This is
then added to the Kaplan-Meier plot of the study group for visual
comparison between these subjects and the population at large. Before
estimating the expected survival we have to specify a different follow-up
time for the study group according to three common methods of computing it.
In the Ederer or "exact" method the subjects in the study cohort are not
censored or dead before the end of a stated follow-up time.
In the Hakulinen method, follow up time is the actual censoring time for
those patients who are censored and the maximum potential follow up for
those who die, i.e. the most optimistic last contact date.
Conditional method (or Ederer II) is simpler in respect of this, because
follow-up time is what it actually is, either the subject dies or not.
A worked example using two ancillaries data files are included in the package.
I would be interested in any your comment, impression and feedback after
the use of stexpect.
