Dasatinib Versus Imatinib In Patients with Newly Diagnosed Chronic Myeloid Leukemia In Chronic Phase (CML-CP) In the DASISION Trial: 18-Month Follow-up

Abstract 206 Background: Dasatinib is 325-fold more potent than imatinib in vitro against unmutated BCR-ABL, and is an established second-line treatment for patients (pts) with CML-CP who are resistant, intolerant or have a suboptimal response to imatinib. The Phase 3 DASISION study compares dasatinib with imatinib as initial treatment for pts with newly diagnosed CML-CP. After a minimum of 12 months (mos) of follow-up, dasatinib 100 mg once daily demonstrated significantly higher and faster rates of complete cytogenetic response (CCyR) and major molecular response (MMR) compared to imatinib 400 mg once daily (Kantarjian, H, et al. N Engl J Med 2010;362:2260). Eighteen-mo follow-up data are presented here. Methods: 519 pts with newly diagnosed CML-CP (median disease duration of 1 mo) stratified by Hasford risk were randomized to either dasatinib 100 mg once daily (n=259), or imatinib 400 mg once daily (n=260). The study design and endpoints have been described previously. All analyses were based on intention-to-treat pts. Results: Median treatment duration at the present analysis was 18 mos for each drug, with 81% of pts in the dasatinib arm and 80% in the imatinib arm still remaining on study drug. Median dose intensity was 99 mg/d for dasatinib and 400 mg/d for imatinib. Efficacy and safety results in the present analysis were consistent with those reported previously after 12 mos of follow-up. The rate of confirmed CCyR (cCCyR, CCyR on consecutive analyses at least 1 mo apart) by 18 mos continued to be higher for dasatinib than for imatinib (78% vs 70%); P=0.0366). Based on time-in-cCCyR (a measure of durability) analysis involving all randomized pts, dasatinib-treated pts were 28% less likely to experience a progression event (as defined by European LeukemiaNet 2006) after achieving a cCCyR or never achieving a cCCyR compared to those on imatinib. The MMR rate at any time was superior for dasatinib compared to imatinib (57% vs 41%, P=0.0002). Based on time-to-response analysis, pts on dasatinib were 1.84-fold more likely to achieve a MMR than those on imatinib (HR=1.84, P <0.0001). Rates of cCCyR in dasatinib-treated pts with low, intermediate and high risk were 92, 71 and 73%, respectively. The corresponding rates in the imatinib arm were 72, 71 and 64%. Rates of MMR in dasatinib-treated pts with low, intermediate and high risk were 63, 56 and 51%, respectively. The corresponding rates in the imatinib arm were 48, 40 and 30%. A BCR-ABL transcript level of ≤ 0.0032% was achieved in 13% dasatinib-treated and 7% imatinib-treated pts. Rates of progression-free survival at 18 mos were 94.9% for dasatinib and 93.7% for imatinib; the corresponding overall survival rates were 96.0% and 97.9%, respectively. Six pts (2.3%) in the dasatinib arm and 11 (4.3%) in the imatinib arm discontinued due to treatment failure as defined by 2006 European LeukemiaNet criteria. Six pts (2.3%) on dasatinib and 9 (3.5%) on imatinib had a transformation to accelerated or blast phase. Discontinuation of treatment due to drug-related adverse events (AEs) was infrequent for both dasatinib (6%) and imatinib (4%). Non-hematologic AEs (all grades) in ≥10% of pts (dasatinib vs imatinib) were fluid retention (23% vs 43%), diarrhea (18% vs 19%), nausea (9% vs 21%), vomiting (5% vs 10%), muscle inflammation (4% vs 19%), myalgia (6% vs 12%), musculoskeletal pain (12% vs 16%), fatigue (8% vs 11%) and rash (11% vs 17%). While superficial edema was less frequent with dasatinib than with imatinib (10% vs 36%), pleural effusion was seen only with dasatinib (12% vs 0%: grade 1, 2%; grade 2, 9%; grade 3, <1%), and did not impact the efficacy. Non-hematologic grade 3/4 AEs were infrequent in either arm (≤1%). Grade 3/4 cytopenias (dasatinib vs imatinib) were anemia (11% vs 7%), neutropenia (22% vs 20%) and thrombocytopenia (19% vs 10%). Two pts (0.8%) on dasatinib and 3 (1.2%) on imatinib had grade 3/4 bleeding. Cytopenia was the reason for discontinuation in 6 pts on the dasatinib arm (2.3%) and 3 on the imatinib arm (1.2%). Conclusions: After 18 mos of follow-up, dasatinib 100 mg once daily continues to demonstrate superior efficacy compared to imatinib. Dasatinib also continues to be generally well tolerated. These results support the potential use of dasatinib as initial treatment for pts with newly diagnosed CML-CP. Disclosures: Shah: Bristol-Myers Squibb, Novartis and Ariad: Membership on an entity's Board of Directors or advisory committees. Kantarjian: BMS, Pfizer and Novartis: Research Funding; Novartis: Consultancy. Hochhaus: Novartis, Bristol-Myers Squibb: Consultancy, Research Funding. Cortes: Brostol-Myers Squibb, Novartis and Wyeth: Honoraria. Bradley-Garelik: Bristol-Myers Squibb: Employment, Equity Ownership. Zhu: Bristol-Myers Squibb: Employment. Baccarani: Novartis, Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.