Molecular recurrence for the 9 patients experiencing a late MRec. Patient are classified based on the length of TFR1. Patients 1 and 6 started TFR 1 and 4 years before 2010, respectively. Sensitivity was fixed at 10 000 ABL1 copies to define PCR negativity in these early days (left x-segment and left y-axis). A sensitivity of 32 000 ABL1 copies to define PCR negativity was applied from 2010 (right x-segment and right y-axis). A sensitivity of 32 000 ABL1 copies was available for patients 2, 3, 4, 5, 7, 8, and 9. All patients experienced a slow kinetic of molecular recurrence. MR4, molecular response 4 log (BCR-ABL1^IS ≤0.01%); MR4.5, molecular response 4.5 log (BCR-ABL1^IS ≤0.0032%). Vertical dotted line: TKI resumption. Black circles indicate undetectable BCR-ABL1 transcripts.