Leukemia, Acute Lymphoblastic (ALL) in Adults

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Acute lymphoblastic leukemia (ALL) results from abnormal proliferation of hematopoietic stem cells in the bone marrow or extramedullary tissue.

Description

ALL in adults is the result of a clonal proliferation, of lymphocyte progenitor cells which are also known as lymphoblasts.

  • ALL is defined by the presence of ≥20% lymphoblasts in the bone marrow (1).
  • ALL subdivided based on the type of white blood cell (WBC) affected: T cell ALL or B cell ALL.
  • B cell ALL is further separated into two major categories based on Philadelphia chromosome status:
    • Philadelphia chromosome negative (Ph−) ALL: further defined by molecular characteristics and subdivided into an additional category called Philadelphia chromosome-like (Ph-like) ALL which carries a poor prognosis.
    • Philadelphia chromosome positive (Ph+) ALL: characterized by the presence of Philadelphia chromosome and classically carried a poor prognosis but now has significant improvement in survival with the advent of treatment regimens incorporating tyrosine kinase inhibitors (TKIs) (often used in chronic myeloid leukemia) (1).
  • Acute lymphoblastic lymphoma (LBL) is a related disease, arising from lymphoblasts. ALL and acute LBL are often managed similarly.
    • LBL presents as a mass, often in the mediastinum, with <20% blasts in the bone marrow.
    • ALL may present with a mass lesion but contains ≥20% blasts in the bone marrow (2).

Pregnancy Considerations
Many chemotherapy (CTX) drugs are teratogenic. Risk/benefit discussions are necessary if diagnosis is made during pregnancy.Pediatric Considerations
ALL is the most common malignancy in children: accounting for 30% of all pediatric malignancies and 80% of pediatric leukemias (See “Acute Coronary Syndromes: NSTE-ACS [Unstable Angina and NSTEMI]; Acute Coronary Syndromes: STEMI.”) (2).Geriatric Considerations

  • Geriatric-aged patients can experience decreased tolerance for classic CTX-based regimens, often have high-risk disease features, and have higher rates of developing treatment-related myeloid neoplasms such as myelodysplastic syndrome and acute myeloid leukemia.
  • Recent advancements in chemo-immunotherapy treatment options for ALL have dramatically improved the tolerability of treatment and survival rates for patients aged >60 years. 4-year survival rates have improved to 80–85% among patients able to receive newer chemo-immunotherapy-based treatments (1).

Epidemiology

Bimodal distribution: early peak around age 5 years, second peak at around age 50 years (2). 80% of cases occur in children, 20% in adults.

Incidence

  • Incidence of ALL is 1.7/100,000 per year (2).
  • In 2024, there were 6,800 new cases of ALL in the United States (1).
  • Higher incidence in older age, males, whites, those with history of radiation, CTX, or certain genetic disorders.

Etiology and Pathophysiology

The pathophysiology of ALL involves the abnormal proliferation and differentiation of clonal lymphoid cells. These malignant cells proliferate and replace the bone marrow cells that would normally create red blood cells, normal WBCs, and platelets. Therefore, resulting in anemia, neutropenia, and thrombocytopenia.

Genetics

There is increased risk of ALL in patients with genetic disorders such as trisomy 21, Klinefelter syndrome, and Fanconi anemia (2).

Risk Factors

  • Age >70 years
  • History of ionizing radiation exposure
  • Human T-cell lymphotropic virus (HTLV) type 1 is associated with adult T-cell ALL.
  • Epstein-Barr virus (EBV) is associated with mature B-cell ALL (2).

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