Comparing crossing survival curves

hi isabel,
You have to decide if focus is on the survival curves or hazards.. 
Crossing hazards do not imply crossing survival curves

If you are dealing with crossing hazards, and you are interested in 
testing for an effect of a covariate (presumably with a crossing hazard 
effect), then a standard Cox model framework based on the martingale 
representation "(start, stop, event)" (rather than "(time, event)") will 
suffice

Finally, if you are interested in estimating the crossing point you 
could have a look to the package flexCrossHaz (currently in the 
Archive.. Let me know if you are interested in becoming maintainer..:-) 
)

http://cran.r-project.org/src/contrib/Archive/flexCrossHaz/

best,
vito


Il 05/07/2012 12.37, Isabel Borges ha scritto:

     Hi
    I want to compare the survival curves in two groups. Because the hazards are
    not proportional (the curves cross) the log rank test or Cox proportional
    hazard test are not suitable. How should such curves be compared? Comands
    are welcome....
    Thanks in advance

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Vito M.R. Muggeo
Dip.to Sc Statist e Matem `Vianelli'
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