The 6-gene signature discriminates early from late CP in independent patient samples by QPCR. Results of leave-one-out cross validation comparing diagnostic early CP (class 0, n = 45) and late CP (class 1, n = 22) patient samples (A) including graphic representation (B). Both early CP patients misclassified at diagnosis as late CP (indicated in the red circles) subsequently did poorly on imatinib mesylate therapy.