Restrospective Multicenter Study Evaluating Efficacy and Safety of Dasatinib and Nilotinib in Patients with Imatinib-Resistant or –intolerant Chronic Myeloid Leukemia in Chronic Phase: Korean CML Working Party

Abstract 1691

Dasatinib and nilotinib have been founded to be effective and well-tolerated in patients who develop resistance or intolerance to imatinib. Not enough data are currently available to recommend one over the other as the preferred second-line therapy based on efficacy data. Therefore we planned a multicenter retrospective study to analyze the efficacy and safety of dasatinib and nilotinib in patients with imatinib-resistant or –intolerant chronic myeloid leukemia in chronic phase. In this Korean multicenter study, 126 patients imatinib-resistant or –intolerant chronic myeloid leukemia in chronic phase were treated with dasatinib (n=76) or nilotinib (n=50) The purpose of this study was to compare rates of cytogenetic and molecular response rate, event-free survival (EFS), progression-free survival (PFS) and overall survival (OS), and toxicities of nilotinib and dasatinib treatment of imatinib-resistant or –intolerant chronic myeloid leukemia in chronic phase. PFS was defined as the time from the start of treatment to the earliest date of any of following event: loss of complete hematologic response (CHR), loss of major cytogenetic response (MCyR), progression to accelerated phase (AP) or blastic phase (BP), discontinuation due to treatment failure as assessed by the clinician, and death from any cause on therapy. Event was defined by any one of the following: loss of CHR, loss of MCyR, progression to AP or BP, discontinuation due to treatment failure as assessed by the clinician, treatment discontinuation due to toxicity, and death from any cause on therapy. For dasatinib and nilotinib group, median ages (51 years old vs. 53), median durations of CML (23.7 months vs. 19.8 ) before receiving dasatinib or nilotinib and duration of prior imatinib treatment (21.7 months vs 17.7) were comparable. Nilotinib group had a higher proportion of intermediate and high sokal scores at the time of diagnosis than dasatinib group (41.5 vs 29.3% (high), 41.5% vs 32.5%(intermediate), 17.1% vs 37.9(low), p= 0.04). After median follow-up durations of 20.2 months of dasatinib group and 25.3 months of nilotinib group, the rates of major molecular response were 50.0% for dasatinib group and 59.6% for nilotinib group (p=NS) and the rates of MCyR (complete and partial cytogenetic response) were 78.4% for dasatinib group and 74.5% for nilotinib group (p=NS). The estimated EFS at 24 months was 67% and 48% in dasatinib and nilotinib group, respectively. (p<0.05). The estimated PFS at 24 months was 85% and 56% in dasatinib and nilotinib group, respectively. (p<0.05) Overall survival rates were comparable in both treatment groups (24-months OS; dasatinib 91%, nilotinib 94%; p=0.65). Both were generally well tolerated. Hematologic toxicities were more frequent among patients receiving dasatinib. 10 patients (13%) had pleural effusion in dasatinib; 9 events were grade 1 or 2. Elevated liver enzyme were more frequent among patients receiving dasatinib. In conclusion, In this study population, nilotinib and dasatinib showed similar cytogenetic and molecular response rates and survival. Toxicity profiles of two drugs were different and both drugs showed tolerable toxicities. In terms of event-free survival and progression-free survival, dasatinib was superior to nilotinib, but caution is warranted in interpretation because baseline characteristics including hematologic and cytogenetic response at the time of start with dasatinib and nilotinib and sokal scores at the time of diagnosis were different.