Medical Health Encyclopedia

Assays that test for cancerous cells are improving, allowing doctors to detect smaller and smaller amounts of hidden disease. For example, flow cytometry assays can detect 0.01% leukemic cells, and PCR assays can detect 0.001% leukemic cells. A new concept called minimal residual disease (MRD) is becoming an important prognostic factor in ALL. A more precise measure of disease response, MRD may soon replace existing measures such as "complete response" and "partial response" when assessing the effectiveness of ALL treatment. Ongoing studies of MRD in ALL may help identify patients in remission who are at risk of relapse. In addition, early therapeutic intervention based on the presence of MRD may improve outcome and prolong survival.

Drawing Conclusions from Cell Characteristics

Using the results of the tests described above, patients are classified into low-, average-, and high-risk groups, which have unique therapies. This information allows the doctor to diagnosis the type of leukemia and plan the best treatment.

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Doctors attempt to make a prognosis and determine an optimal treatment plan by assessing all the cell characteristics plus the white blood cell count. As examples:

• Patients who have an L1 or L2 morphology, a white blood cell count of less than 15,000 mm3, a t(12;21) genetic translocation, and a cALLa-positive antigen marker have an excellent outlook.
• On the other hand, patients who have an L2 morphology, a white blood cell count greater than 30,000 mm3, and who lack the cALLa marker have a poorer prognosis and require more aggressive treatment.