Disease progression refers to the clinical worsening of a hematologic condition or its transformation into a more aggressive malignancy.
For your board exams, you should focus on these two specific types of progression:
1. MDS Transformation to AML
The most critical type of progression mentioned is the transformation of Myelodysplastic Syndrome (MDS) into secondary Acute Myeloid Leukemia (AML). While MDS is characterized by “ineffective hematopoiesis” (the marrow failing to make enough healthy cells), progression to AML involves the “uncontrolled proliferation” of immature, non-functional cells called blasts.
Clinical markers of progression in MDS include:
- Increasing Blast Counts: A rise in the percentage of bone marrow blasts (e.g., jumping from <5% to >5% or >10%).
- Worsening Cytopenias: A significant further decline in blood counts, such as a drop in hemoglobin $\ge 2$ g/dL or becoming dependent on transfusions.
- Clonal Evolution: Acquiring new cytogenetic or molecular mutations, which often increases the risk of transformation and worsens survival.
2. AML Treatment Failure or Relapse
In the context of AML, progression typically means:
- Induction Failure: The disease does not respond to initial intensive chemotherapy, and the patient fails to achieve a complete remission (CR).
- Relapse: The reappearance of leukemic cells in the marrow or blood after a patient has already achieved a remission.
A major goal of therapy, particularly for higher-risk MDS, is to delay this progression to improve quality of life and prolong survival.
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