[R] Power calculation for survival analysis

Duke derek.cyr at duke.edu
Wed Sep 21 15:54:20 CEST 2011

I am trying to do a power calculation for a survival analysis using a
logrank test and I need some help properly doing this in R.  Here is the
information that I know:
- I have 2 groups, namely HG and LG
- Retrospective analysis with subjects gathered from archival data over 20
years. No new recruitment of subjects and no estimated time to target
accrual and accrual rate.
- Survival measured in both groups at 1 year, 3 years, 5 years.
- Assume 50% survival for LG and 30% survival for HG at 5 years.
- Assume a 6 month difference in overall survival to be statistically
- Total sample size is ~ N=500 with 15% of subjects comprising the LG group;
85% make up the HG group.

The main hypothesis is that HG group has shorter overall survival than LG

Can someone please help me out with how to properly calculate the power for
such a situation using R? This is new to me.


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