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Background: B-lineage acute lymphoblastic leukemias (B-ALL) harboring the t(9;22)(q34;q11)/BCR::ABL1 rearrangement represent a category with previously dismal prognosis whose management and outcome dramatically changed thanks to the use of tyrosine kinase inhibitors (TKIs) usage and more recently full chemo-free approaches. The prompt identification of these cases represents an important clinical need. Objectives: We sought to identify an optimized cytofluorimetric diagnostic panel to predict the presence of Philadelphia chromosome (Ph) in B-ALL cases by the introduction of CD146 in our multiparametric flow cytometry (MFC) panels. Methods: We prospectively evaluated a total of 245 cases of newly diagnosed B-ALLs with a CD146 positivity threshold >10% referred to the Division of Hematology of 'Sapienza' University of Rome. We compared the results of CD146 expression percentage and its mean fluorescence intensity (MFI) between Ph+ ALLs, Ph-like ALLs, and molecularly negative ALLs. Results: Seventy-nine of the 245 B-ALL cases (32%) did not present mutations at molecular testing, with 144/245 (59%) resulting in Ph+ ALL and 19/245 (8%) Ph-like ALLs. Comparing the 3 groups, we found that Ph+ B-ALLs were characterized by higher expression percentage of myeloid markers such as CD13, CD33, and CD66c and low expression of CD38; Ph+ B-ALL showed a higher CD146 expression percentage and MFI when compared with both molecular negative B-ALL and Ph-like ALLs; neither the mean percentage of CD146 expression neither CD146 MFI were statically different between molecular negative B-ALL and Ph-like ALLs. Conclusions: Our data demonstrate the association between CD146 expression and Ph+ ALLs. CD146, along with myeloid markers, may help to identify a distinctive immunophenotypic pattern, useful for rapid identification in the diagnostic routine of this subtype of B-ALLs that benefits from a specific therapeutic approach.
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INTRODUCTION: Chronic myeloid leukemia (CML) prevalence is currently increasing due to the great efficacy of tyrosine kinase inhibitor (TKI) therapy. Discontinuation of treatment in the long-term, owing to avoid off-target side effects or treatment-free remission (TFR), has become an additional treatment goal in CML patients who achieved a deep molecular response (DMR). Second-generation TKIs (2 G-TKIs) have a significantly higher rate of DMR than imatinib. Hence, especially in young patients with a strategy of TFR, 2 G-TKIs are becoming the most frequently used TKIs and may increase TFR attempts in the future. AREAS COVERED: In this review, the main findings extrapolated from clinical trials and real-life evidence regarding 2 G-TKIs discontinuation were discussed, through broad research on Medline, Embase, and archives from EHA and ASH congresses. EXPERT OPINION: Overall, TFR rate after 2 G-TKIs is ranging from 40% to 60% for selected patients with sustained DMR and it can be considered a safe procedure, that have become, nowadays, a daily practice. However, many crucial aspects regarding treatment choices, timings, as well as predictive factors, patient communication, and optimal strategies need to be better clarified to improve successful TFR rate.