Treatment of chronic-phase chronic myeloid leukemia in patients randomized to dasatinib or imatinib after suboptimal responses to three months of imatinib therapy: final 5-year results from DASCERN.

Early molecular response (EMR) at 3 months is predictive of improved overall survival (OS) and progression-free survival (PFS) in patients with chronic myeloid leukemia in the chronic phase (CML-CP). Although about one-third of patients treated with first-line imatinib do not achieve EMR, long-term OS and PFS are still observed in most patients. DASCERN (NCT01593254) is a prospective, phase IIb, randomized trial evaluating a switch to dasatinib in patients who have not achieved EMR after 3 months of treatment with first-line imatinib. Early analysis demonstrated an improved major molecular response (MMR) rate at 12 months with dasatinib versus imatinib (29% vs. 13%, P=0.005). Here, we report results from the final 5-year follow-up. In total, 174 patients were randomized to dasatinib and 86 to remain on imatinib. Forty-six (53%) patients who remained on imatinib but subsequently experienced failure were allowed to cross over to dasatinib per protocol. At a minimum follow-up of 60 months, the cumulative MMR rate was significantly higher in patients randomized to dasatinib versus imatinib (77% vs. 44%, P.