Imatinib discontinuation is safe in patients with chronic myeloid leukemia (CML) who have sustained deep molecular response with no late molecular recurrence, according to long-term follow-up of the French Stop Imatinib Study (STIM1).

Over a median follow-up of 77 months after treatment discontinuation in 100 patients with CML who had undetectable minimal residual disease (UMRD) for at least 2 years, 61 lost UMRD after a median of 2.5 months, and 1 died with UMRD at 10 months, Gabriel Etienne, MD, of Institut Bergonie, Bordeaux, France, and colleagues reported online in the Journal of Clinical Oncology.

Of the 61 patients who lost UMRD, 57 restarted treatment and 55 achieved a second UMRD at a median of 4.3 months. The median time to second UMRD in patients with molecular recurrence with or without loss of major molecular response at the time of relapse was 4.2 months and 5 months, respectively. At a median of 73 months, none of the patients with molecular recurrence experienced CML progression. The rate of molecular recurrence-free survival overall was 43% at 6 months, 40% at 18 months, and 38% at 60 months, the investigators reported ( 2016 Oct. 3. doi: 10.1200/JCO.2016.68.2914 ).

These final long-term results of the STIM1 trial confirm the safety of imatinib discontinuation in CML patients with deep molecular response, and “make treatment-free remission legitimate as a criterion of treatment evaluation in the future,” the investigators concluded, noting that the possibility of improved results in patients treated with second-generation tyrosine kinase inhibitors as first- or second-line therapy is currently being evaluated in ongoing discontinuation trials.