I'm wondering about this question:
short version: how to adequately compare the effect of a reclassification of the same subjects on survival
long version: I have one cancer cohort that was sorted into TNM classes long time ago. The definition of the classes has now been updated and I like to know if, say, class 1 of the old classification has a better/worse survival than class 1 of the updated classification. My problem is that the cohort stays the same, only the sorting into classes changes.
Mini example: patients 1,2 are in class I_old and patients 3,4 in class II_old, patient 1 stays in class I_new but patient 2 goes to class II_new, patient 3 stays in II_new, patient 4 changes to I_new. If I want to compare the effect of the reclassification in class I, I would have to compare the survival of patients 1 and 2 versus the the survival of patients 1 and 4. So patient 1 is in both of the groups.
I doubt that the standard procedures like logrank test are adequate here. But what can be done? I have a very vague idea about proportional hazards regression with a time varying covariate (namely indicator for "before" and "after" update) or a frailty model but cannot tell at all if I'm going in the right direction.
What do you think?