Acute Lymphoblastic Leukemia

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DESCRIPTION

  • Acute lymphoblastic leukemia (ALL) is a hematopoietic malignancy that results from a malignant proliferation of immature white blood cells (WBCs) (B cells and T cells).
  • Risk group classification for B-cell ALL:
    • Infant ALL: age <1 year
    • Standard risk ALL: age 1 to <10 years; initial WBC count <50,000/μL
    • High-risk ALL: age ≥10 years; WBC ≥50,000/μL
  • Further risk stratification for B-cell ALL is based on multiple factors including National Cancer Institute (NCI) criteria (age and WBC count), biologic, cytogenetic characteristics, and response to initial therapy. This classification determines the intensity of therapy and prognosis.
  • T-cell ALL does not have a standard risk stratification. The key prognostic determination is minimal residual disease (MRD) response at the end of induction and the end of consolidation therapy.
  • Other poor prognostic factors
    • Corticosteroid pretreatment
    • Evidence of central nervous system (CNS) or testicular disease

EPIDEMIOLOGY

  • ALL is the most common childhood malignancy.
  • Accounts for approximately 35% of cancer in children
  • More common in White and male children
  • ALL incidence: 3 to 4 cases per 100,000 per year
  • Peak incidence is between ages 2 and 5 years

RISK FACTORS

  • Prior cancer therapy (chemotherapy or radiation)
  • Monozygotic twin with ALL
  • Specific genetic syndromes

Genetics

  • Associated genetic syndromes
    • Trisomy 21 (Down syndrome)
    • Fanconi anemia
    • Bloom syndrome
    • Shwachman-Diamond syndrome
    • Ataxia telangiectasia
    • Diamond-Blackfan anemia
  • Neurofibromatosis type 1
  • Li-Fraumeni syndrome (a familial cancer syndrome due to P53 gene mutation)
  • Congenital immunodeficiencies (Wiskott-Aldrich syndrome)

PATHOPHYSIOLOGY

  • Leukemia arises from lymphoid progenitor cells that have sustained multiple specific genetic damages that lead to malignant transformation and proliferation, lack of cell maturation, and resistance to normal cell death processes (apoptosis).
  • This lymphoblastic proliferation replaces the normal bone marrow precursor cells, causing ineffective hematopoiesis and infiltration of lymphatic tissue and end organs.

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