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st: Relative survival - strel

From   Sam Leary <>
Subject   st: Relative survival - strel
Date   Thu, 06 Oct 2011 11:07:26 +0100

Dear all, I am a bit of a novice at survival analysis, but am trying to calculate relative survival using strel. My variables are

death_5y = 1 if died by 5 years after diagnosis, 0 if still alive at 5 years
age_diag = age at diagnosis (years)
age_death = age at death or 5 years, whichever came first (years)

I have downloaded a lifetable which has the following variables:
country calendar_year sex age rate
and I have only kept the data for the calendar year relating to the start date of my audit. I have also sorted this file by age then sex.

So I have used the following commands to calculate the crude and relative survival at 5 years after diagnosis:

stset age_death, failure(death_5y) origin(age_diag)
strel 0 5 using "ltab_s1",mergeby(sex)

My question is, as there are 257 deaths out of a total of 468, why is the crude survival percentage 41.86 using strel, rather than (468-257)/468 = 45.1?

Many thanks,


Dr Sam Leary
Senior Lecturer in Statistics

Working hours:
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Lifecourse Epidemiology and Population Oral Health Research Group
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