Hi there,

I need some help to figure out what is the proper model in survival analysis
for my data.
Subjects were randomized to 3 treatments in trial 1, some of them experience
the event during the trial;
After period of time those subjects were randomized to 3 treatments again in
trial 2, but different from what they got in 1st trial, some of them
experience the event during the 2nd trial (I think the carryover effect can
be ignored since the time between two trials is long enough.)

What I am interested is whether the survival functions differ among
treatments. How should I deal with the correlation between the observation
since the same subject was treated with two different drugs in two trials?
Should I add "TRIAL" , "whether the event happened before", or "number of
times the event happened before" as covariate(s)?

Any input will be appreciated. Thank you.
Qian

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