{MEDSTATS} competing risk model with time dependent covariates under R or Splus
Philippe, The machinery to use is to split follow-up time so finely that you can safely assume that rates are constant in each interval, and then just stuff it all into a Poisson model. This allows you to use any kind of time-dependent variables as well as accommodating competing risks. In the Epi package (http://staff.pubhealth.ku.dk/~bxc/Epi/) on CRAN there is a machinery for representation and manipulation of multistate data (of which competing risks are a special case), see the function Lexis(). It also has a time-splitting function there, splitLexis(). If you take a look at practical 14 from this year's SPE course: http://staff.pubhealth.ku.dk/~bxc/SPE/2008/pracs.pdf there is an example that addresses the problem you are having, practical no. 14. If go to the folder http://staff.pubhealth.ku.dk/~bxc/SPE/2008/R you will find the R-code that runs the solution to the practical. The data used is a part of the Epi-package, so you just have to load the Epi package first. It is however not using the Fine/Gray approach, but is directly modelling the cause-specific rates taking time dependent covariates into account. Best regards, Bendix ______________________________________________ Bendix Carstensen Senior Statistician Steno Diabetes Center Niels Steensens Vej 2-4 DK-2820 Gentofte Denmark +45 44 43 87 38 (direct) +45 30 75 87 38 (mobile) bxc at steno.dk http://www.biostat.ku.dk/~bxc
-----Original Message-----
From: MedStats at googlegroups.com
[mailto:MedStats at googlegroups.com] On Behalf Of pguardio
Sent: 26. juli 2008 22:47
To: MedStats
Subject: {MEDSTATS} competing risk model with time dependent
covariates under R or Splus
Dear members,
is there a way to perform a competing risk model which can
handle time dependent covariates under either R ou SPlus ?
my main covariate (additional treatment to patients) violates
the proportional hazards assumption, its effect being
observed after one year of the main treatment, not before
(this is expected / makes sense on a clinical point of view).
So I was planning to use a time dependent Cox model with 2
time intervals for patients: < > 1 year etc...
However, I need to use a competing risk model because a large
number of patients dies from early toxicity from main
treatment (not related to the additional treatment I m
evaluating the effect) or from events unrelated to the
disease or the treatments (elderly patients).
Therefore, to analyze the effect of my covariate of interest
on disease free survival and relapse incidence, I d like to
use a competing risk model such as the Gray CMPRSK.
However, I cannot have multiple "lines" for the same patient
(cluster function is not allowed in CMPRSK) with this package
(for time dep covariates I need 1 or 2 lines with same Id /UPN).
Does anyone knows how can I manage this in CMPRSK ?
Any help will be greatly appreciated
Thanks
Yours sincerely
Philippe Guardiola