Hello,
I am trying to estimate a sample size for the log rank test comparing two different treatment arms.
The study will have a three year followup when the effect of the treatment will change after each year.
the input I am using is:
proc power;
twosamplesurvival test=logrank
Alpha = 0.05
curve("trt1") = 1:0.65 2:0.53625 3:0.489328125
curve("trt2") = (1 to 3 by 1):(0.82 0.7462 0.712621)
groupsurvival = "trt1" | "trt2"
accrualtime = 2
Totaltime = 3
groupmedlosstimes = 10 | 10
groupweights = (1 2)
power = 0.90
EVENTSTOTAL=.
;
Run;
This program designs a piecewise linear effect. Can I choose an ascending or descending linear effect?
Also, I want to define a piecewise exponential?
And last, Can I define the effect in hazard ratio terms and not survival curve but with a changing hazard ratio over time?
Thank you!
