Long-Term Follow-up of Chronic Phase Chronic Myeloid Leukemia Patients Who Failed Interferon Alpha and Switched to Imatinib

Abstract 3742

Few data were reported about the long-term outcome of patients treated with imatinib after interferon-alpha (IFN) failure. Recently, MDACC group reported a 10-year survival rate of 68%. We report here the outcome of 134 adult Ph+ CML patients who switched to imatinib after IFN failure. Response criteria used are in accordance to ELN guidelines; survival was calculated from start of imatinib until death for any cause, progression-free survival (PFS) was calculated from start of imatinib to advent of accelerated/blastic phase or death for any cause and event-free survival (EFS) was calculated from start of therapy to development of any event leading patient to discontinue the drug. There were 74 males and 60 females, median age was 47 years. Median follow-up was 96 months. Sokal score identified 66 patients as low risk, 49 patients as intermediate and 17 as high risk, whereas Eutos score identified 107 patients as low risk and 10 patients as high risk. Overall, 103 patients (76.8%) achieved a CCyR as their best cytogenetic response and 68 (51%) achieved a MMR, after a median time of 52 months. Complete molecular remission (CMR, undetectable transcript according to ELN recommendations) was achieved as the best response in 60 patients after a median follow-up of 76 months. The estimated 9-year overall survival rate was 74%, the PFS rate was 71% and the EFS was 54%. Progression to accelerated/blastic phase was detected in 19 patients. Due to resistance or intolerance to imatinib, 22 patients switched to dasatinib (12 patients for cytogenetic resistance, 5 patients for intolerance, 2 for molecular resistance and 3 for BC) and 17 patients switched to nilotinib (11 patients for cytogenetic resistance and 6 for molecular resistance): 18 patients (64%) achieved or maintained CCyR and 11 patients (35%) achieved MMR. Achieving at 12 months a CCyR or an MMR was associated with a significant better OS in the long-term (82%) as compared to less than PCyR (70%) or only CHR (12%). Baseline factors that correlated with a poor OS were clonal cytogenetic evolution, higher percentage of basophils and blast cells in peripheral blood, high Sokal and Eutos score, whereas age did not correlate with a worse OS. The results of our study support the validity of rescuing with imatinib patients failing IFN, with an estimated 9-year survival rate of 74% that is similar to that reported in other recent studies.