CONICET | Buscador de Institutos y Recursos Humanos

The development of tyrosine kinase inhibitors (TKI) has produced a true revolution in the treatment and prognosis of patients with chronic myeloid leukemia (CML), since they act specifically inhibiting the oncoprotein BCR-ABL1 responsible of the etiopathogenesis of the disease. Most CML patients with chronic phase achieve profound molecular responses (MR), which determine a very low risk of progression and a high rate long-term survival. Several clinical trials have shown that patients with sustained deep and stable molecular response can safely discontinue TKI therapy, achieving treatment-free remission (TFR). Objective: Determine the frequency of cases with typical BCR-ABL1 transcripts (b2a2 or b3a2) that achieve deep MR (≥ 4.0 log reduction) sustained for ≥ 24 months in patients with CML treated with TKIs for ≥ 54 months and monitored at the National Academy of Medicine, from Buenos Aires, Argentina in order to estimate the number of cases that would be able to be included in a discontinuation program in the real life. Methods: RNA extraction was performed from a peripheral blood sample. The quantification of BCR-ABL1 transcripts was performed by qRT-PCR using the Molecular MD kit and the Rotor Gene (Qiagen) equipment. WHO calibrators were used to inform in International Scale.Results: From 2009 to date, 2,449 patients were studied in our Center. Of these, only 539 patients had an uninterrupted treatment for at least 54 months (range of 54 to 96 months). Within this cohort, 192/539 (36%) cases were identified with deep MR (≥ 4.0, ≥4.5 or ≥5.0 log reduction), sustained for a period ≥ 24 months (range 24-72 months). The remaining patients, 347/539 (64%) had MR