The variables used in this study included sex, CML duration, months' performance status, splenomegaly, prior interferon therapy, peripheral blood, bone marrow, best cytogenetic response to Imatinib, second-generation Nilotinib or Dasatinib therapy, active disease at the start of the second course of TKIs, clonal evaluation, higher than 90% Ph positivity, and IC50 for Nilotinib and Dasatinib for in vitro inhibition of kinase activity of the mutated point in BCR-ABL. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.