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Abstract
Most patients with chronic phase CML in treatment with tyrosine kinase inhibitors (TKI) achieve profound molecular responses, which determine a very low risk of progression and a high rate longterm survival. Several clinical trials have shown that patients with sustained deep and stable molecular response can safely discontinue ITK therapy, achieving treatment-free remission (TFR). The logarithmic reduction of the BCR-ABL1 transcripts in international scale (IS) defines the level of depth that the patient has achieved after treatment. The MR4.0, MR4.5 or MR5.0 correspond to ≤ 0.01%, ≤ 0.0032%, and ≤ 0.001% transcript levels respectively. The objective of this work was to determine the frequency of cases with typical BCR-ABL1 transcripts (b2a2 or b3a2) that achieve deep molecular response (MR ≥ 4.0) sustained for ≥ 24 months in patients with CML treated with ITKs for ≥ 54 months and monitored at the National Academy of Medicine, in order to estimate the number of cases that would be able to be included in a discontinuation protocol in the real life. From 2009 to date, 2.449 patients were studied. Of these, only those cases that had a follow-up of at least 54 uninterrupted months (range of 54 to 96 months) were selected, which allowed to choose a group of 539 cases. Within this cohort, 192/539 (36%) cases were identified with deep MR ≥ 4 logs reduction (MR4.0, MR4.5, MR5.0), sustained for a period ≥ 24 months (range 24-72 months); the remaining patients, 347/539 (64%) had MR < 4.0. Analyzing our casuistry we have been able to identify a group of 192 cases that represent 8% (192/2449) of the total of patients monitored in our center that would be able to discontinue treatment under strict molecular control.
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