After 5 years of follow-up, patients with chronic-phase chronic myeloid leukemia (CML) who were treated with dasatinib experienced greater rates of major molecular response (MMR) and molecular response (MR), but similar rates of overall survival (OS) and progression-free survival (PFS) compared with patients treated with imatinib. Jorge Cortes, MD, University of Texas MD Anderson Cancer Center, Houston, Texas, USA, presented the final 5-year data from the Phase 3 Study of Dasatinib vs Imatinib in Patients With Newly Diagnosed Chronic Phase CML [DASISION; NCT00481247].

Dasatinib is a first-line treatment for patients with chronic-phase CML. In the DASISION trial, patients with chronic-phase CML who received dasatinib demonstrated higher rates of complete cytogenic response (CCyR) and a faster rate of attaining MR with an acceptable safety profile compared with patients who received imatinib [Kantarjian H et al. N Engl J Med. 2010]. The purpose of the present analysis was to determine the long-term outcomes of patients who completed a minimum of 5 years of follow-up.

The multicenter DASISION trial randomly assigned 519 treatment-naïve patients with chronic-phase CML to receive dasatinib 100 mg QD (n = 259) or imatinib 400 mg QD (n = 260) [Kantarjian H et al. N Engl J Med. 2010]. The primary end point of confirmed CCyR by 12 months was reached by 77% of patients in the dasatinib arm compared with 66% of patients in the imatinib arm (P = .007).

By 5 years, the MMR rates were 76% and 64% in the dasatinib and imatinib arms, respectively (P = .0022); the difference between the 2 arms remained similar over the 5-year period. MR was achieved by 42% and 33% of patients in the dasatinib and imatinib arms, respectively (P = .0251). However, the 5-year OS and PFS were similar among both arms, with rates of 91.5% (HR, 1.01; 95% CI, 0.58 to 1.73) and 85.5% (HR, 1.06; 95% CI, 0.68 to 1.66), respectively. A greater number of patients in the imatinib arm (7.3%) experienced transformation to accelerated or blastic phase CML compared with the dasatinib arm (4.6%).

Table 1 outlines the outcomes at 5 years in relation to the MR at 3 months; patients in both treatment groups whose BCR-ABL levels were ≤ 10% at 3 months had better outcomes.

In addition, 5-year OS, PFS, and transformation-free survival were significantly higher in patients whose BCR-ABL levels were ≤ 10% at 3 months in both arms of the study compared with patients whose BCR-ABL levels were > 10% (Table 2).

Treatment failure occurred in 10 patients in the dasatinib arm and 14 patients in the imatinib arm, and disease progressed in 18 patients in the dasatinib arm and 23 patients in the imatinib arm. Mutations were identified in some patients whose treatment failed or disease progressed, and most of these patients discontinued the study early.

Important adverse events included pleural effusion, which occurred in 28% of patients who received dasatinib and only 1% of patients who received imatinib. In addition, arterial ischemic events such as myocardial infarction, angina pectoris, coronary artery disease, acute coronary syndromes, and transient ischemic attack occurred more frequently in the dasatinib arm. Other adverse events reported more frequently in the dasatinib arm included abdominal pain and headache, whereas facial edema, muscle spasms, myalgia, nausea, and vomiting occurred more frequently in the imatinib arm.

In conclusion, Dr Cortes stated that the 5-year data from the DASISION trial support the data from earlier analyses showing that dasatinib treatment resulted in higher rates of MMR and MR, faster time to MR, and less frequent transformation to accelerated or blastic CML. No new safety signals occurred. Although arterial ischemic events were more frequent with dasatinib treatment, they were uncommon.