The achievement of an early complete cytogenetic response is a major determinant for outcome in patients with early chronic phase chronic myeloid leukemia treated with tyrosine kinase inhibitors.

We analyzed the association between achievement of early complete cytogenetic response (CCyR) and event-free survival (EFS) and overall survival (OS) in patients with newly diagnosed chronic myeloid leukemia in chronic phase treated with imatinib 400 mg (n = 73), or imatinib 800 mg daily (n = 208), or second- generation tyrosine kinase inhibitors (n = 154). The overall CCyR rates were 87%, 91%, and 96%, respectively (P = .06); and major molecular response (MMR) rates were 77%, 87%, and 89%, respectively (P = .05). Their 3-year EFS rates were 85%, 92%, and 97% (P = .01), and OS rates were 93%, 97%, and 100% (P = .18), respectively. By landmark analysis, patients with 3-, 6-, and 12-month CCyR had significantly better outcome: 3-year EFS rates of 98%, 97%, and 98% and OS rates of 99%, 99%, and 99%, respectively, compared with 83%, 72%, and 67% and 95%, 90%, and 94%, in patients who did not achieve a CCyR. Among patients achieving CCyR at 12 months, the depth of molecular response was not associated with differences in OS or EFS. In conclusion, second tyrosine kinase inhibitors induced higher rates of CCyR and MMR than imatinib. The achievement of early CCyR remains a major determinant of chronic myeloid leukemia outcome regardless of whether MMR is achieved or not.