By Laura Cowen
Italian research shows that long-term imatinib discontinuation is feasible outside of a clinical trial setting for patients with chronic myeloid leukaemia (CML) who achieve stable undetectable molecular disease (UMD) with front-line treatment.
The team, led by Dario Ferrero from Universitá degli Studi di Torino in Turin, Italy, found that 15% of 93 unselected patients treated with the tyrosine kinase inhibitor (TKI) imatinib for chronic phase CML since 2001 experienced sustained treatment-free remission once they stopped imatinib therapy.
Among the participants, 60 had a major molecular response (MMR) with imatinib but only 26 achieved a stable UMD - defined as a MR with a 4 or 4.5 log-reduction of BCR-ABL1 transcripts from baseline - for at least 2 years and were therefore eligible for treatment discontinuation.
In total, 22 patients discontinued therapy (four refused this option) and at a median follow-up of 36 months, 12 (13% of the study population) remained off therapy. Of these, five had persistently negative tests for BCR-ABL1, five had a transitory positive BCR-ABL1 test, and two lost and regained a MR at least once.
The median relapse time for 10 patients who had to resume TKI therapy was 5 months, and the researchers point out that all of these patients regained deep MR without CML progression.
Ferrero and team also note that four additional patients with MR or MMR but not UMD stopped imatinib because of intolerance or patient's decision. Two patients restarted imatinib after 3 and 33 months but two patients remained off therapy at 81 and 82 months after treatment discontinuation, respectively.
Therefore, 15% of the 93 CML patients achieved long-lasting, treatment-free remission.
The researchers report in the British Journal of Haematology that sustained treatment-free remission was not significantly associated with age, previous interferon treatment, Sokal risk group, UMD duration or TKI treatment duration.
"Our results, in agreement to published experiences of clinical trials, outline the safety and feasibility of imatinib discontinuation in a real life context for patients in stable UMD", Ferrero and co-authors conclude.
Noting that trials are now investigating the ability to discontinue second-generation TKI treatment as front-line or second-line therapy, they add that "it is important to assess the actual proportion of imatinib-treated patients who can achieve a long-term safe discontinuation, in order to better clarify the benefit of second generation TKI in this setting."
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