unknown 1). BCR-ABL transcript types were b2a2 (n = 74, 40%), b3a2 (n = 89, 48%), or b2a2/b3a2 (n = 22, 12%). At 3 months patients with BCR-ABL>10% IS were 51 (28%), and depth of response in early responders was as follows: MR1 (n = 67, 36%), MR2 (n = 56, 30%), or MR3 (n = 11, 6%). At 6 months patients with no MR, MR1, MR2, MR3, and MR4 were 36 (19%), 44 (24%), 53 (29%), 39 (21%) and 13 (7%), respectively. With a median duration of imatinib therapy of 50 months (range 3-165), 86 (46%) patients never achieved DMR, 33 (18%) had an unstable DMR and 66 (36%) reached a sDMR. Overall, patients with MR2 or better at 3 months had a cumulative incidence of sDMR of 70.0% (95% CI: 54-80.5%) at 5 years, significantly superior to those with MR1 or no MR (p = 0.006) Similarly, cumulative incidence of sDMR at 5 years was significantly different across level of MR, ranging from 13.4% (95%CI 0-29.4%) for MR1 to 78.6% (95%CI 56.1-89.6%) for MR3 or better (p < 0.001). Patients with b3a2 or b3a2/b2a2 transcripts had a higher probability of sDMR compared to those with b2a2 transcript (60.3% vs 44.6%, p = 0.018). Considering the impact of transcript type across different depth levels of MR, we found that among patients with MR1 at 3 months, those with b3a2 had a significantly higher probability of sDMR (39.5% vs 16.7%, p = 0.029), Summary/Conclusion: This real-life, retrospective study suggests that patients with very good MR after 3 or 6 months of standard dose imatinib, defined as BCL-ABR IS ratio ≤1% and ≤0.1% respectively, have a high probability of achieving a sDMR, a prerequisite for therapy discontinuation. Among patients with BCR-ABL ≤10% but >1% at 3 months, b3a2 transcript identifies patients with a higher possibility of subsequent sDMR.
