Treatment-Free Remission by Tyrosine Kinase Inhibitor for Patients with Chronic Myeloid Leukemia

The prospective French cessation trial, Stop Imatinib trial (STIM) represents a breakthrough in Treatment-Free Remission (TFR) research in Chronic Myeloid Leukemia (CML) treatment with Tyrosine Kinase Inhibitors (TKIs). About 40% had long-term complete molecular response (CMR) after imatinib cessation in STIM trial. It demonstrated that imatinib cessation might be possible in monotherapy if CMR can be achieved and maintained for a certain period of time. TFR is targeted to avoid late side effects and allow fertile females to become pregnant and bear children as well as to save the treatment costs and health economics of TKI treatment. The predictive factors contributing to the success of TFR were reported in prospective clinical trials and retrospective observations. They are as follows: (1) Sokal score, (2) imatinib treatment duration, (3) history of interferon-a treatment, and (4) the duration of CMR before cessation. In addition, (5) polymorphisms of ABCG2 421A/C, (6) the BIM common deletion polymorphism, and (7) the increase in the proportion of NK cells or reduction of regulatory T cells are potential biomarkers for predicting TFR. In this review, we discussed TFR as a treatment target of CML, and some conditions for successful TFR in CML treatment