Description

ALL in adults is the result of a clonal proliferation, survival, and impaired differentiation of immature lymphocytes. These early lymphoid cells take the place of normal hematopoietic cells in the bone marrow, affecting any organ.

• The World Health Organization (WHO) defines ALL as the presence of ≥25% lymphoblasts in the bone marrow; the US uses ≥20% as the cutoff.
• ALL and lymphoblastic lymphoma (LBL) can arise from the same precursor cell lineage and 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.

Pregnancy Considerations
Many chemotherapy (CTX) drugs are teratogenic.

Pediatric Considerations
ALL is the most common malignancy in children: accounts for 30% of all pediatric malignancies and 80% of pediatric leukemias (see “Acute Lymphoblastic Leukemia, Pediatric”) (1).

Geriatric Considerations
Patients aged >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.

Epidemiology

Bimodal distribution: early peak around age of 5 years, second peak at around age of 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 2021, 5,690 new cases of ALL in the United States
• Higher incidence in older age, males, whites, those with history of radiation, CTX, or certain genetic disorders

Prevalence
Prevalence of ALL can range from 15% to 50% and increases with age.

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, neutrophils, and platelets; therefore, resulting in anemia, neutropenia, and thrombocytopenia

Genetics

• Higher rates in monozygotic and dizygotic twins
• Increased risk of ALL with diseases related to chromosomal instability and inherited chromosomal abnormalities (2).

Risk Factors

• Age >70 years, radiation and CTX exposure, and infection with HIV (2).
• Human T-cell lymphotropic virus type 1 is associated with adult T-cell ALL.
• Epstein-Barr virus is associated with mature B-cell ALL.