No Benefit from Hydroxyurea Pre-Treatment in Frontline Chronic Myeloid Leukemia Therapy and Evidence of Quantitative Changes in the BCR::ABL1 Transcript Level

Hydroxyurea (HU) cytoreduction is usually administered to patients with chronic myeloid leukemia before starting any tyrosine kinase inhibitors (TKIs) therapy. However, up to date, there is no evidence of any benefit of hydroxyurea pre-treatment. Conversely, evidence has been provided on both the prognostic significance of the quantitative assessment of <i>BCR::ABL1</i> expression at diagnosis and the individual decline of the <i>BCR::ABL1</i> slope. In this view, we assumed that any kind of treatment administered before a confirmed diagnosis of chronic myeloid leukemia might change the amount of <i>BCR::ABL1</i> transcript levels. To this purpose, we evaluated leukocyte counts and <i>BCR::ABL1</i> quantitative expression either at diagnosis (baseline and no therapy) and on day 7 and day 14 of treatment in a cohort of 45 unselected patients with newly diagnosed chronic myeloid leukemia in the chronic phase. After informed consent, 21 of them received HU cytoreduction for 14 days before starting TKI treatment (HU group), whereas the other 24 patients received frontline TKI therapy without HU pre-treatment (TKI group). Our findings showed that: (i) there is no benefit from HU cytoreduction in patients affected with chronic myeloid leukemia before starting treatment with TKIs; (ii) any kind of therapy administered before a confirmed diagnosis of chronic myeloid leukemia might change the amount of <i>BCR::ABL1</i> expression levels.