29th May 2023

Acute lymphoblastic leukaemia (ALL)

Overview

Acute lymphoblastic leukaemia is similar to AML, but the progenitor cells are lymphoid blast cells rather than myeloid. Mostly, these cells are B-cells in origin, but they can also be T-cells. In contrast to AML, most cases present in childhood, and it is the most common cancer in children. The peak age is between 2-4 years old.

Like AML, as the blast clone increases in size it causes progressive cytopenia. However, in ALL it is more common to see lymphadenopathy and extramedullary tissue infiltration, especially testicular. Central nervous system (CNS) disease is also significantly more common in ALL.

Investigations

• Full panel of bloods, especially
  • FBC – often anaemia and thrombocytopenia. WCC may be raised (due to blasts), normal or low. Neutropenia is common
  • Coagulation screen – to look for DIC
  • Blood film – often shows circulating blasts. Can be hard to distinguish from AML but cytoplasm is more basophilic and less granular, and Auer rods will not be present
  • It may be possible to perform flow cytometry (immunophenotyping) on peripheral blood to confirm the diagnosis, plus cytogenetics and molecular genetic analysis
• Bone marrow aspirate and trephine are essential to confirm the presence of blasts – diagnosis usually requires 20% blast percentage in the marrow. Flow, cytogenetics, and molecular studies are also performed on this sample
• Lumbar puncture – CNS disease is more common at presentation than with AML

Further tests can include echo/MUGA scan pre-chemo.

Treatment

Treatment consists of intense chemotherapy, with much of it being delivered as an inpatient. It consists of an induction phase, a consolidation phase and then maintenance treatment. This also incorporates treatment that can penetrate the blood brain barrier (for CNS disease prophylaxis). The regimens differ depending on the age of the patient and the results of cytogenetic analysis. In children over the age of 1, cure rates are up to 90%, but this is considerably lower in adults and infants. Higher WCC at diagnosis is associated with poor outcomes. Also, certain cytogenetic abnormalities confer a worse prognosis, such as t(9;22) Philadelphia chromosome.