Abstract only 6504 Background: In the phase 3 DASISION trial of dasatinib v IM in patients (pts) with newly diagnosed CML-CP, dasatinib had higher 12-month rates of complete cytogenetic response (CCyR) and major molecular response (MMR) (Kantarjian, NEJM 2010;362:2260). By 12 months confirmed CCyR (cCCyR) rates for dasatinib v IM were 77% v 66%, P=0.001, meeting the primary endpoint. Methods: Pts were randomized to receive dasatinib 100 mg once daily (QD; n=259) or IM 400 mg QD (n=260). Results: Minimum 24-month follow-up (median 26.6 months) is reported here. 24-month molecular response rates were higher for dasatinib v IM: MMR (BCR-ABL ≤0.1%) 64% v 46%, P<0.0001; MR 4 (BCR-ABL ≤0.01%) 29% v 19%, P=0.0053; MR 4.5 (BCR-ABL ≤0.0032%) 17% v 8%, P=0.0032. MMR rates were higher for dasatinib in all Hasford risk groups (high 73% v 56%; intermediate 61% v 50%; low 73% v 56%). Of pts who achieved MMR at 12 months, on dasatinib v IM, 97% v 92% had maintained their MMR at 24 months, respectively. Pts receiving dasatinib v IM had faster responses; median time to CCyR and MMR was 3.2 v 6.0 and 15 v 36 months, respectively. In an intent-to-treat analysis, fewer pts receiving dasatinib (n=9; 3.5%) transformed to accelerated/blast phase v IM (n=15; 5.8%) on study or during follow-up after discontinuation. 24-month overall and progression-free survival were similar for dasatinib v IM: 95.4% v 95.2% and 93.7% v 92.1% (follow-up is ongoing). Few additional adverse events (AEs) were reported between 12 and 24 months in both arms, with grade 3/4 nonhematologic AE rates ≤1%. In each arm, 10 pts had a BCR-ABL mutation detected at time of discontinuation. For dasatinib v IM, 23% v 25% discontinued treatment for drug-related AEs (7% v 5%), progression (5% v 7%), failure (3% v 4%), unrelated AEs (2% v <1%), death (2% v <1%), and other (4% v 8%). Few pts discontinued between 12 and 24 months for dasatinib (n=19; 7%) and IM (n=16; 6%). Conclusions: Updated data with minimum 36-month follow-up will be presented, including mutation analyses in pts who discontinued, progressed, or had suboptimal response. Pts receiving dasatinib had a lower transformation rate and higher molecular responses v pts receiving IM, supporting the use of dasatinib in newly diagnosed CML-CP.