Leukemia (blood cancer, leukemia, lymphosarcoma) is a whole group of tumors characterized by uncontrolled proliferation and varying degrees of differentiation of hematopoietic cells. With all this, leukemic cells are descendants, clones of one mutated cell.
The cause of leukemia, as a rule, are chromosomal aberrations, i.e. changes in the structure of chromosomes as a result of various processes of rearrangement of their structure: translocation, deletion, inversion, fragmentation.
According to the traditional classification, all leukemias are divided into acute (AL) and chronic (CL). This division is associated with the different ability of these tumors to differentiate proliferating cells.
In the case of acute leukemia, differentiation is practically absent, a huge number of immature, non-functional blast cells accumulate in the blood, which leads to inhibition of the normal hematopoiesis of all germs. These signs are detected in the blood in more than 80% of cases. Chronic leukemia (leukemia) produces a population of differentiated cells, traditionally granulocytic, gradually replacing normal peripheral blood cells.
Acute leukemias are usually divided into lymphoblastic and myeloblastic.
Acute lymphoblastic leukemia (ALL) most often develops from precursors of B-lymphocytes (within 75% of cases). There are also B-ALL and T-ALL. Cytogenetically, the presence of the Philadelphia chromosome matters.
Acute myeloid leukemia (acute myeloid leukemia) is often referred to as “non-lymphoblastic leukemia” to emphasize its diversity and difference from ALL, as blasts with all this can be of granulocytic, erythrocyte and even platelet origin. Acute non-lymphoblastic leukemia is histologically classified with the letter M followed by numbers from 0 to 7, for example, M7 is acute megakaryoblastic leukemia.
Chronic leukemia in children is quite rare and is also a heterogeneous group of diseases:
- chronic lymphocytic leukemia is characterized by the proliferation of small lymphocytes in the bone marrow, peripheral blood, as well as lymph nodes, spleen and liver;
- chronic myeloid leukemia (CML) is characterized by stem cell proliferation, which is often accompanied not only by an increase in the number of granulocyte precursors, but also by erythrocytes and platelets. A distinctive feature is the cytogenetic feature – the presence of the Philadelphia chromosome, as well as the phase of the disease. Distinguish a slow phase, an acceleration phase and a final phase of a disease;
- hairy cell leukemia is characterized by the proliferation of well-differentiated B-lymphocytes with the development of pancytopenia and splenomegaly. The disease is characteristic of the elderly and more often in males.
Leukemia is diagnosed by a combination of blood and bone marrow tests.
When diagnosing, it is not the clinical picture that is decisive, but the cytogenetics, morphology and immunology of the detected blasts. Not only the final diagnosis, but also the prognosis, treatment and outcome of the disease will depend on the parameters detected with all this.
The prognosis for leukemia is generally more favorable in childhood (1–9 years), it also depends on the type of pathology, the type of cells and the periods of detection of the disease.
Chemotherapy is the mainstay of treatment for leukemia. Treatment today is protocol-based, and therefore each type of pathology and its individual features are important for choosing a treatment protocol. In acute leukemia, treatment is based on polychemotherapy. Its efficiency is higher in acute lymphocytic lecosis up to 95%. In acute myeloid leukemia, the effectiveness of chemotherapy exceeds 80%, but it is often accompanied by complications, and a 5-year remission is observed only in 40% of patients, while relapses in ALL are no longer a frequent occurrence. In the treatment of CML, the effectiveness of chemotherapy is not 20-40%.
The best results so far are obtained by allogeneic bone marrow transplantation. Good results are obtained by alpha-interferon therapy. In recent times, great hopes are placed on products that block the tyrosine kinase activity of the Bcr-Abl protein, for example, the product STI-571. It is believed that such products can be used for maintenance monotherapy, ie. for the prevention of blast crises. In general, leukemia therapy must be carried out in a specialized department, with the likelihood of using the most modern and effective treatment, which guarantees both a high probability of complete remission and complete recovery after the entire complex of therapeutic measures.