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), whereas the National Comprehensive Cancer Network (NCCN) 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 patientsGenetics
- 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.