An estimated 40%–60% of CML patients with long-term achievement of deep molecular responses (a prerequisite for a discontinuation attempt) can successfully discontinue TKI treatment and reach treatment-free remission (TFR), in other words, continue in major molecular response (MMR, BCR::ABL1 (IS) ≤ 0.1%) after treatment is stopped [5, 6]. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.