Leukemia, Acute Lymphoblastic (all) in Adults
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- Acute lymphoblastic leukemia (ALL) in adults is the result of a clonal proliferation, survival, and impaired differentiation of immature lymphocytes. The World Health Organization (WHO) defines ALL as the presence of ≥25% lymphoblasts in the bone marrow (1). Nevertheless, the National Comprehensive Cancer Network uses a ≥20% as cutoff (2).
- ALL and lymphoblastic lymphoma (LBL) can arise from the same precursor cell line, and therefore can be considered diseases along the same spectrum:
- LBL presents as a mass, possibly but not limited to the mediastinum, with <25% blasts in the bone marrow.
- ALL may present with a mass lesion but contains ≥25% bone marrow involvement.
- Any organ can be affected
Many chemotherapy (CTX) drugs are teratogenic.
ALL is the most common malignancy in children—it accounts for 30% of all pediatric malignancies, and 80% of pediatric leukemias (see “Acute Lymphoblastic Leukemia, Pediatric”).
Patients >60 years with ALL have a 42% mortality during induction CTX. The cause of death is usually CTX related complications or relapse. Survival is often reduced due to poor tolerance of CTX, thus leading to dose reductions and ineffective medication delivery.
- Incidence of ALL is 1.7/100,000 per year.
- Higher incidence in males, whites, those with history of radiation, CTX, or certain genetic disorders
- Bimodal distribution: early peak at 4 to 5 years of age, second peak at ~50 years
- 80% of cases occur in children, 20% in adults.
Etiology and Pathophysiology
Unknown in most patients
- Higher rates in monozygotic and dizygotic twins
- Increased risk of ALL with diseases related to chromosomal instability: Bloom syndrome, Fanconi anemia, ataxia-telangiectasia, neurofibromatosis
- Increased risk with inherited chromosomal abnormalities: Down syndrome, Klinefelter syndrome, etc.
- See “Follow-Up Tests & Special Considerations.”
- Age >70 years, radiation exposure, and infection with HIV are risk factors for developing ALL.
- Human T-cell lymphotropic virus type 1 is associated with adult T-cell ALL.
- Epstein-Barr virus is associated with mature B cell ALL.