Hi BUGS users,
I'm tying to fit a mixed treatment comparison, using 3 trials comparing 4
treatments. I would like to determine the median survival time for each
treatment. The baseline is treatment 1, from the first trial. My code is the
following :
model {
#prior for basic parameters
d12 ~ dnorm(0,.001) # log hazard ratio 1 vs 2
d23 ~ dnorm(0,.001) # log hazard ratio 2 vs 3
d14 ~ dnorm(0,.001) # log hazard ratio 1 vs 4
l1 ~ dnorm(0,.001) # log hazard rate for 1 (baseline)
#define functional parameters
d13 <- d12 + d23
#define absolute hazards on log scale
lpac ~ dnorm(l1,ppac)
l2 <- l1 - d12
l3 <- l1 - d13
l4 <- l1 - d14
#define absolute hazards on natural scale
log(a) <- l1
log(b) <- l2
log(c) <- l3
log(d) <- l4
#convert to mean survival
OSa <- 1/a
OSb <- 1/b
OSc <- 1/c
OSd <- 1/d
#likelihood
y12 ~ dnorm(d12,p12)
y23 ~ dnorm(d23,p23)
y14 ~ dnorm(d14,p14)
}
data;
list(y12=0.3436,y23=0.2546,y14=0.2469,p12=9.6008,p23=9.7682,p14=9.3067,lpac=
-4.3737,ppac=?????)
inits;
list(d12=.01,d23=.01,d14=.01,l1=.01)
My problem stands on the initial value for the precision of the hazard rate
for treatment 1 at baseline. How can I calculate it if I dispose of :
- N in each arm for the baseline trial
- % censored
- median survival time ?
Thanks very much
Stéphanie Payet
REES France
Réseau d'Evaluation en Economie de la Santé
28, rue d'Assas
75006 PARIS
Tél. +33 (0)1 44 39 16 90
Fax +33 (0)1 44 39 16 92
Mèl. [log in to unmask]
Site Internet : http://www.rees-france.com
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