medwireNews: Final DASISION study findings confirm dasatinib to be an effective, long-term treatment for patients with a new diagnosis of chronic phase–chronic myeloid leukaemia (CP–CML).

After 5 years, 61% of 259 patients randomly assigned to receive dasatinib 100 mg/day were still taking the tyrosine kinase inhibitor (TKI), while 63% of the 260 patients started on imatinib 400 mg/day continued with their treatment, the investigators report in the Journal of Clinical Oncology.

The primary endpoint of complete cytogenetic response (CCyR) at 5 years had been achieved by 28% of dasatinib-treated patients and 26% of their imatinib-treated counterparts, although the researchers note that these values may have been higher if bone marrow samples had been tested in the patients at the end of the study.

Cumulative 5-year rates of major molecular response (MMR) and molecular responses  with a 4.5-log (MR^4.5) reduction in  BCR–ABL1 transcripts from baseline were also comparable in the dasatinib and imatinib treatment arms, at 76% versus 64%, and 42% versus 33%, respectively, say Jorge Cortes, from the University of Texas MD Anderson Cancer Center in Houston, USA, and co-authors.

Five-year estimated overall survival was 91.0% for the dasatinib group and 90.0% for those given imatinib. And estimated progression-free survival was a corresponding 85.0% and 86.0% with 4.6% and 7.3% of patients transforming to accelerated or blast phase CML during a period of follow-up that continued beyond TKI discontinuation.

In all, 84% of dasatinib-treated patients and 64% of imatinib-treated patients achieved BCR–ABL1 of 10% or less within 3 months of treatment. Compared with patients who did not reach this target, these individuals were more likely to achieve CCyR, MMR and MR^4.5 over 5 years, had higher rates of overall and progression-free survival, and were less likely to have transformation.

Cortes et al note that no new adverse effects were reported for dasatinib or imatinib by the end of the 5-year study period and just 15% and 11% of adverse effects were grade 3 or 4 in the groups, respectively.

Patients given dasatinib had higher rates of grade 3 or 4 neutropenia (29 vs 24%), anaemia (13 vs 9%) and thrombocytopenia (22 vs 14%) but lower rates of other nonhaematological side effects, except for any grade of pleural effusion (28.0 vs 0.8%). Discontinuation for drug-related side effects occurred in 16% and 7% of dasatinib- and imatinib-treated patients, respectively.

Pulmonary hypertension was reported in 5.0% and 0.4% of the dasatinib and imatinib groups, respectively, with 12 of the 14 diagnoses deemed to be drug related. Arterial ischaemic events were “uncommon” in both groups, affecting 5.0% and 2.0%, respectively.

However, there was a “disproportionate number” of deaths from infection in the dasatinib versus imatinib groups (11 vs 1), with seven deaths reported between 69 days and 4.5 years after dasatinib discontinuation.

“It will be important to prospectively and intentionally look at a possible imbalance in the occurrence of infections and, if present, determine a possible mechanism(s) for dasatinib-related infectious complications”, the investigators comment.

“These results suggest that first-line dasatinib should continue to be considered a standard first-line therapy for patients with newly diagnosed CML-CP”, the researchers conclude.

While patients given dasatinib were more likely to achieve early treatment milestones, the authors explain that the high rates of CCyR and overall survival in both treatment arms mean a longer follow-up period and larger study population are likely needed to demonstrate any significant difference in survival between the TKIs.

By Lynda Wiliams, Senior medwireNews Reporter

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