Prognosis
Once a diagnosis of leukemia has been made, further tests are performed to check:
- Whether the cells are myeloid or lymphocytic
- Stage of maturity of the ALL B cell
- Specific markers, or immunologic features, on the surface of the cancer cell
- The genetic makeup of the cells ( cytogenetics)
- The physical characteristics of the cells ( morphology)
Determining the Cell of Origin
First, the doctor must determine the cell of origin. In other words, they want to determine if the cell is myeloid or lymphocytic. One method is to measure an enzyme called terminal deoxynucleotidyl transferase (TdT).
- About 95% of all ALL types (except the subtype B cell) have elevated TdT.
- Only about 20% of cases of acute myeloid leukemia (AML) express TdT, however, so its use in determining the cell line is limited.
B-Cell Maturity
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The stage of maturity of the leukemic B cell helps determine prognosis. There are three stages:
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Early precursor-B. Approximately 80% of patients with ALL have the early precursor-B subtype, which is the least mature. It also offers the best prognosis.
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Precursor-B. This is the intermediate stage.
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B cell. This is the mature cell and ALL in this stage is identical to Burkitt's non-Hodgkin's lymphoma. It is therefore treated differently from other ALL cases.
Immunological Markers
A series of tests are used to determine the immunologic pattern of the leukemia cell (how it can be expected to interact with the immune system).
On the surface of malignant ALL cells are markers for certain antigens (molecules that set off a targeted attack by the immune system using antibodies). Such antigens are proving to be very helpful in predicting outcome.
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| An antigen is a substance that can provoke an immune response. Typically, antigens are substances not usually found in the body. |
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