Promyelocytic blast crisis of chronic myelogenous leukemia during imatinib treatment

Ischemic stroke as a presenting feature of promyelocytic blast phase in chronic myeloid leukemia - an uncommon presentation: a case report and literature review in the post imatinib era

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm (MPN characterized by reciprocal translocation in the ABL1 and BCR region of chromosomes 9 and 22 respectively. Progression to the blast phase in chronic myeloid leukemia results in a poorer prognosis. It can be of either myeloid, lymphoid or a mixed lineage. Progression to the promyelocytic blast phase is very rare, and there are no evidence-based guidelines for its management. Thrombosis in CML is not well defined. Thrombosis can be seen in patients with acute promyelocytic leukemia (APL) with venous thrombosis (VTE) being more common than arterial thrombosis. Ischemic stroke as the presenting feature of blast phase progression in CML is extremely rare. We report a case of CML who presented to us with acute ischemic stroke and subsequently was diagnosed as CML transformed to the promyelocytic blast phase. She was successfully treated with dasatinib along with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO).

Promyelocytic Blast Crisis of Chronic Myeloid Leukemia in a Patient Undergoing Therapy with a Tyrosine Kinase Inhibitor

A 58-year-old male with the chronic phase of chronic myeloid leukemia (CML), treated with a tyrosine kinase inhibitor (TKI), bosutinib, since the past two years, presented with bright red bleeding per rectum and disseminated intravascular coagulation. A bone marrow biopsy reverse transcription-polymerase chain reaction revealed a promyelocytic blast crisis, with leukemic cells displaying both BCR/ABL and PML/RARα chimeric genes. Cytogenetic studies revealed translocations of both t(15;17) and t(9;22). With the initiation of all-trans retinoic acid, arsenic trioxide and gemtuzumab, the patient achieved remission, with absent PML/RARα by fluorescence in situ hybridization analysis. This case highlights the importance of long-term monitoring of patients with CML, especially those on TKIs, for the development of secondary leukemias in the future.

Mechanisms of Disease Progression and Resistance to Tyrosine Kinase Inhibitor Therapy in Chronic Myeloid Leukemia: An Update

Chronic myeloid leukemia (CML) is characterized by the presence of the BCR-ABL1 fusion gene, which encodes a constitutive active tyrosine kinase considered to be the pathogenic driver capable of initiating and maintaining the disease. Despite the remarkable efficacy of tyrosine kinase inhibitors (TKIs) targeting BCR-ABL1, some patients may not respond (primary resistance) or may relapse after an initial response (secondary resistance). In a small proportion of cases, development of resistance is accompanied or shortly followed by progression from chronic to blastic phase (BP), characterized by a dismal prognosis. Evolution from CP into BP is a multifactorial and probably multistep phenomenon. Increase in BCR-ABL1 transcript levels is thought to promote the onset of secondary chromosomal or genetic defects, induce differentiation arrest, perturb RNA transcription, editing and translation that together with epigenetic and metabolic changes may ultimately lead to the expansion of highly proliferating, differentiation-arrested malignant cells. A multitude of studies over the past two decades have investigated the mechanisms underlying the closely intertwined phenomena of drug resistance and disease progression. Here, we provide an update on what is currently known on the mechanisms underlying progression and present the latest acquisitions on BCR-ABL1-independent resistance and leukemia stem cell persistence.

Phenotype of blasts in chronic myeloid leukemia in blastic phase-Analysis of bone marrow trephine biopsies and correlation with cytogenetics

We identified different phenotypic subsets among 62 cases of chronic myeloid leukemia (CML) in blast crisis (BC) (26% B-lymphoblastic, and 74% various myeloblastic subsets) on bone marrow trephines and correlated the blast-phenotype with cytogenetics. Five of myeloid-BC had an associated 3q26 abnormality and two of these showed a megakaryoblastic-phenotype. While myeloid-BC was associated with additional copies of Philadelphia (Ph) (29%) (p=0.08), numerical abnormalities (51%) (p=0.007), trisomy-8 (29%) (p=0.08) and 17p-loss (22%), none of lymphoid-BC showed these abnormalities. Among myeloid-BC, CD34-negative cases were more often associated with trisomy-8, 17p-loss and numerical abnormalities, and the CD117-negative subset with additional copies of Ph (p<0.05).