It is evident that people vary in their response to Glivec, but there is not presently any way of predicting that variable.
Some work has recently been done in Australia where measurement of an enzyme in patients before and after treatment may be able to predict responses, and as a result may be useful in dtermining for example what is the optimum dose of Glivec for a specific patient.
Clearly an advantage for anyone starting Glivec, to be able to adjust the dose to the individual.
See the link below for more of the technical details
Paul