[R] ROC for threshold value, biometrics

[myint.tin-tin-htar@jvr.ap-hop-paris.fr]

Hello,

I am just a beginner of R 1.9.0.
I try to construct a predictive score for the development of liver
cancer in cirrhotic patients. So dependant variable is binanry (cancer
yes or no). Independant variables are biological data. The aim is to
find out a cut-off value which differentiate (theoratically)  from
normal to pathological state for each biological data.

How can I step in procedue to get a cut-off value (threshold) for each
variable? I think I should try by ROC. But I'm not sure. If so, someone
can lead me?
If not, someone can advice me how ?

Any advice will be cordially aprreciated.

Tin Tin Htar Myint
Research assistant
Liver unit
Jean Verdier Hospital, Bondy
France