Can Chronic Myeloid Leukemia (CML) occur without eosinophilia?

From the Guidelines

Yes, chronic myeloid leukemia (CML) can occur without eosinophilia. While eosinophilia is sometimes seen in CML patients, it is not a required diagnostic feature of the disease. CML is primarily characterized by the presence of the Philadelphia chromosome, which results from a reciprocal translocation between chromosomes 9 and 22, creating the BCR-ABL fusion gene 1. This genetic abnormality leads to the production of a constitutively active tyrosine kinase that drives the excessive proliferation of myeloid cells. The diagnosis of CML is based on a combination of clinical findings, complete blood count showing leukocytosis with left shift (immature granulocytes in peripheral blood), bone marrow examination, and cytogenetic or molecular testing to confirm the presence of the Philadelphia chromosome or BCR-ABL fusion.

Some key points to consider in the diagnosis and management of CML include:

• The presence of eosinophilia is not a diagnostic criterion for CML, and many patients have normal eosinophil counts at diagnosis 1.
• Treatment decisions are based on the presence of the BCR-ABL mutation rather than eosinophil counts 1.
• Tyrosine kinase inhibitor therapy is a highly effective first-line treatment option for all patients with newly diagnosed chronic phase CML 1.
• The absence of eosinophilia does not rule out CML, and a comprehensive diagnostic workup is necessary to confirm the diagnosis 1.

In terms of the most recent and highest quality evidence, a 2020 study published in the Journal of the National Comprehensive Cancer Network found that CML is defined by the presence of the Philadelphia chromosome, and that tyrosine kinase inhibitor therapy is a highly effective first-line treatment option for all patients with newly diagnosed chronic phase CML 1. Therefore, the presence or absence of eosinophilia should not influence treatment decisions in CML, and all patients with a confirmed diagnosis of CML should be considered for tyrosine kinase inhibitor therapy.

From the Research

Definition and Characteristics of CML

• Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of the Philadelphia chromosome, which is defined by the BCR::ABL1 oncogene 2, 3, 4, 5.
• The Philadelphia chromosome is a result of a balanced genetic translocation, t(9;22)(q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2 3, 4, 5.

CML and Eosinophils

• There is no direct mention of eosinophils in the provided studies as a characteristic or diagnostic feature of CML 2, 3, 4, 5, 6.
• The studies focus on the genetic characteristics, diagnosis, therapy, and monitoring of CML, but do not discuss the presence or absence of eosinophils in CML patients.

Diagnosis and Treatment of CML

• CML is typically diagnosed based on the presence of the Philadelphia chromosome and the BCR::ABL1 fusion oncogene 2, 3, 4, 5.
• Treatment options for CML include tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, bosutinib, and nilotinib, as well as allogeneic stem cell transplantation 2, 3, 4, 5.