Acute lymphoblastic leukemia (ALL) is a malignant disorder of hematopoietic progenitor cells characterized by uncontrolled proliferation and accumulation of immature lymphoid precursor cells (lymphoblasts) in the bone marrow, peripheral blood, and extramedullary tissues.

ALL results in failure of normal blood cell production causing:

• Anaemia

• Neutropenia

• Thrombocytopenia

The disease may also occur due to infiltration of leukemic cells into:

• Lymph nodes

• Liver

• Spleen

• Central nervous system

• Testes

• Other organs

ALL is the most common childhood cancer and also occurs in adults, where it generally has a more aggressive course.

Epidemiology

ALL occurs worldwide and affects all age groups.

Epidemiological characteristics include:

• Most common acute leukemia in children

• Represents approximately 75–80% of childhood acute leukemias

• Occurs less frequently in adults

• Has a peak incidence between 2–5 years of age

• Adult ALL has poorer prognosis compared with childhood disease

• Slight male predominance

Risk factors

Genetic abnormalities

Associated genetic conditions include:

• Down syndrome

• Other inherited chromosomal disorders

• Genetic abnormalities affecting lymphoid development

Previous chemotherapy or radiotherapy

Therapy-related ALL may occur following exposure to:

• Cytotoxic chemotherapy

• Radiation therapy

Radiation exposure

Exposure to high levels of ionizing radiation increases risk.

Viral infections

Some cases are associated with:

• Human T-cell lymphotropic virus type 1 (HTLV-1), particularly adult T-cell leukemia/lymphoma

Immunodeficiency states

Increased risk occurs with:

• Congenital immunodeficiency

• HIV infection

• Immunosuppressive therapy

Pathophysiology

ALL results from malignant transformation of lymphoid precursor cells.

The process involves:

1. Genetic mutations affecting lymphoid cell development

2. Uncontrolled proliferation of lymphoblasts

3. Replacement of normal bone marrow cells

4. Reduced production of normal blood cells

5. Infiltration of tissues by leukemic cells

ALL is classified according to cell lineage:

• B-cell ALL (most common)

• T-cell ALL

Bone marrow replacement causes:

• Reduced red cell production → anaemia

• Reduced neutrophil production → infection risk

• Reduced platelet production → bleeding tendency

Clinical presentation

Clinical features result from:

1. Bone marrow failure

2. Leukemic cell infiltration

3. Increased tumour burden

Presentation may be acute and rapidly progressive.

Symptoms

Symptoms due to anaemia

• Fatigue

• Weakness

• Shortness of breath

• Dizziness

• Reduced exercise tolerance

Symptoms due to neutropenia

• Fever

• Recurrent infections

• Mouth ulcers

• Sore throat

Symptoms due to thrombocytopenia

• Easy bruising

• Petechiae

• Bleeding gums

• Nose bleeding

• Heavy menstrual bleeding

Symptoms due to leukemic infiltration

Lymph node involvement

• Enlarged lymph nodes

Hepatosplenic involvement

• Abdominal discomfort

• Abdominal fullness

Bone involvement

• Bone pain

• Joint pain

Central nervous system involvement

• Headache

• Vomiting

• Seizures

• Altered consciousness

Testicular involvement

• Testicular enlargement or discomfort

Clinical signs

General examination

• Pallor

• Fever

• Weight loss

• Reduced performance status

Lymphatic system

• Cervical lymphadenopathy

• Generalized lymphadenopathy

Abdominal examination

• Hepatomegaly

Splenomegaly

Musculoskeletal examination

• Bone tenderness

• Joint tenderness

Neurological examination

Findings may include:

• Cranial nerve palsies

• Focal neurological deficits

• Signs of raised intracranial pressure

Differential diagnosis

• Acute myeloid leukemia (AML)

• Chronic lymphocytic leukemia

• Chronic myeloid leukemia blast crisis

• Lymphoma with bone marrow involvement

• Aplastic anaemia

• Severe viral infections causing cytopenias

• Myelodysplastic syndrome

Diagnostic criteria

Diagnosis of ALL requires:

• Presence of increased lymphoblasts in bone marrow or peripheral blood

• Usually ≥20% lymphoblasts in bone marrow

Confirmation requires:

• Bone marrow aspiration and biopsy

• Flow cytometry immunophenotyping

• Cytogenetic and molecular evaluation

Investigations

Laboratory investigations

Full blood count (FBC)

May show:

• Anaemia

• Thrombocytopenia

• Abnormal white cell count

Peripheral blood film

May demonstrate:

• Circulating lymphoblasts

Renal function tests

• Urea

• Creatinine

• Electrolytes

Required before chemotherapy.

Liver function tests

Assess baseline hepatic function.

Coagulation profile

Performed to assess bleeding risk.

Bone marrow examination

Bone marrow aspiration and trephine biopsy

Required for:

• Diagnosis

• Classification

• Assessment of remission

Immunophenotyping

Flow cytometry

Determines:

• B-cell or T-cell lineage

• Expression of leukemia-associated markers

Cytogenetic and molecular investigations

Used for:

• Risk classification

• Prognosis assessment

• Treatment selection

Central nervous system assessment

Lumbar puncture and cerebrospinal fluid examination

Performed to detect CNS involvement and guide CNS-directed therapy.

Cardiac assessment

ECG and echocardiography

Performed before anthracycline-containing chemotherapy.

Staging and classification

ALL is classified according to:

• WHO classification of hematological malignancies

• Immunophenotype

• Cytogenetic and molecular abnormalities

Unlike solid tumours, ALL does not use TNM staging.

Risk classification is based on:

• Age

• White cell count at diagnosis

• Genetic abnormalities

• Response to treatment

• Minimal residual disease status

Management

Treatment of ALL is complex and requires specialist hematology care.

The goals of treatment are:

• Achieve complete remission

• Prevent relapse

• Eradicate residual leukemia cells

• Prevent CNS relapse

Management consists of:

1. Induction therapy

2. Consolidation/intensification therapy

3. Maintenance therapy

4. CNS prophylaxis

5. Stem cell transplantation in selected patients

Treatment selection depends on:

• Patient age

• Disease risk group

• Immunophenotype

• Molecular abnormalities

• Response to initial therapy

Non-pharmacological treatment

Supportive care

Includes:

• Blood transfusion support

• Infection prevention and treatment

• Nutritional support

• Psychological support

Tumour lysis syndrome prevention

Includes:

• Adequate hydration

• Monitoring renal function and electrolytes

• Uric acid monitoring

• Use of urate-lowering therapy when indicated

CNS prophylaxis

Because ALL frequently involves the central nervous system, preventive CNS therapy is required.

Methods include:

• Intrathecal chemotherapy

• Systemic chemotherapy with CNS penetration

Hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation may be considered in:

• High-risk ALL

• Relapsed ALL

• Patients with poor response to chemotherapy

Pharmacological treatment

Intensive chemotherapy

Treatment regimens vary according to age and risk category.

The recommended intensive regimen includes:

Hyper-CVAD/MTX-ARA-C regimen

This regimen combines alternating chemotherapy cycles.

Components include:

Hyper-CVAD phase

• Cyclophosphamide

• Mesna

• Vincristine

• Doxorubicin

• Dexamethasone

MTX-ARA-C phase

• Methotrexate

• Cytarabine

• Leucovorin rescue

All administered intravenously according to specialist chemotherapy protocols.

Treatment phases

Induction phase

Aim:

• Achieve complete remission

• Reduce leukemic burden

Consolidation/intensification phase

Aim:

• Eliminate residual leukemic cells

• Reduce relapse risk

Maintenance phase

Aim:

• Maintain remission

• Prevent recurrence

Usually involves prolonged oral chemotherapy according to protocol.

Management according to disease characteristics

Philadelphia chromosome-positive ALL

Patients with BCR-ABL1 positive disease require addition of targeted therapy with tyrosine kinase inhibitors according to specialist protocols.

CNS involvement

Management includes:

• Intrathecal chemotherapy

• Intensified systemic therapy

• Specialist neurological monitoring

Relapsed ALL

Management options include:

• Salvage chemotherapy

• Targeted therapies where indicated

• Allogeneic stem cell transplantation

Referral

All suspected or confirmed ALL patients require urgent referral to specialized hematology services.

Urgent referral indications

• Abnormal blood counts with circulating blasts

• Severe infection with neutropenia

• Active bleeding

• Suspected CNS involvement

• Hyperleukocytosis

• Tumour lysis syndrome

Complications

Disease-related complications

• Severe infection

• Anaemia

• Bleeding

• Tumour lysis syndrome

• CNS involvement

• Organ infiltration

Treatment-related complications

Chemotherapy complications

• Febrile neutropenia

• Mucositis

• Infertility

• Cardiotoxicity

• Hepatotoxicity

• Secondary malignancies

Prognosis

Prognosis depends on:

• Age at diagnosis

• Initial white blood cell count

• Immunophenotype

• Cytogenetic abnormalities

• Response to induction therapy

• Minimal residual disease status

Children generally have excellent outcomes with modern therapy.

Adults have more variable outcomes, particularly older patients and those with high-risk genetic abnormalities.

Prevention

Primary prevention

• Avoid unnecessary exposure to ionizing radiation

• Reduce occupational exposure to carcinogenic chemicals

• Prevention and treatment of immunodeficiency states

Secondary prevention

• Early evaluation of unexplained cytopenias

• Prompt investigation of persistent fever, bleeding, or lymphadenopathy

Tertiary prevention

• Regular hematology follow-up

• Monitoring for relapse

• Management of long-term treatment complications