Leukaemia (Adult)

1. Overview

Leukaemia represents a heterogeneous group of clonal haematological malignancies characterised by the uncontrolled proliferation of abnormal white blood cells (WBCs) in the bone marrow and peripheral blood. These malignant cells disrupt normal haematopoiesis, leading to bone marrow failure with consequent anaemia, thrombocytopenia, and functional neutropenia. [1]

Leukaemias are fundamentally classified along two axes: cell lineage (myeloid vs lymphoid) and clinical tempo (acute vs chronic). This yields four principal categories: acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL), chronic myeloid leukaemia (CML), and chronic lymphocytic leukaemia (CLL). Each subtype has distinct molecular pathogenesis, clinical presentation, prognostic markers, and therapeutic strategies. [2]

The advent of molecular diagnostics and targeted therapies has revolutionised leukaemia management. Tyrosine kinase inhibitors (TKIs) have transformed CML from a fatal disease to one with near-normal life expectancy. All-trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) has made acute promyelocytic leukaemia (APL) one of the most curable malignancies. Novel agents targeting BTK, BCL-2, and FLT3 have significantly improved outcomes in CLL and AML. [3,4]

Acute leukaemias are medical emergencies requiring rapid diagnosis and initiation of chemotherapy. Complications such as neutropenic sepsis, tumour lysis syndrome, and disseminated intravascular coagulation (DIC) are life-threatening and demand immediate recognition and management. Chronic leukaemias may have indolent courses, with many CLL patients never requiring treatment, though disease transformation remains a concern. [5]

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2. Epidemiology

Incidence and Prevalence

Leukaemia accounts for approximately 3% of all cancers and 3.5% of cancer deaths globally. In the United Kingdom, approximately 10,000 new cases are diagnosed annually, with significant variation by subtype. [6]

Age Distribution

Leukaemia incidence increases with age, particularly for AML and CLL. The median age at diagnosis for AML is 68 years, with only 40% of patients under 60 years. In contrast, ALL shows a bimodal distribution with peaks in early childhood (2-5 years) and older adulthood (> 50 years). [7]

Ethnicity and Geography

CLL is more common in Western populations and extremely rare in East Asian populations, suggesting genetic predisposition. AML incidence is relatively uniform across ethnicities. CML incidence is slightly higher in Hispanic populations. ALL has higher incidence in Hispanic children compared to other ethnic groups. [8]

Temporal Trends

The incidence of acute leukaemias has remained relatively stable over the past three decades. However, CLL incidence has increased, potentially due to improved diagnostic capabilities and increased use of routine blood counts. Five-year survival has improved significantly: from 42% in 1990 to 65% in 2020 for all leukaemias combined, driven primarily by advances in AML and CML treatment. [6]

Risk Factors

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3. Aetiology & Pathophysiology

Fundamental Mechanisms

Leukaemogenesis is a multistep process involving the sequential accumulation of genetic and epigenetic alterations in haematopoietic stem or progenitor cells. These alterations confer a proliferative advantage, impair differentiation, and enable evasion of apoptosis. [1]

Key Pathogenic Events

1. Chromosomal Translocations: Generate fusion oncogenes (e.g., BCR-ABL1, PML-RARA, MLL rearrangements)
2. Point Mutations: Activate signalling pathways (FLT3-ITD, NPM1, KRAS, NRAS) or disrupt tumour suppressors (TP53, CDKN2A)
3. Epigenetic Dysregulation: Alter gene expression without DNA sequence changes (IDH1/2, TET2, DNMT3A mutations)
4. Aberrant Cell Signalling: Constitutive activation of growth pathways (PI3K/AKT, RAS/MAPK, JAK/STAT)
5. Apoptosis Evasion: Overexpression of anti-apoptotic proteins (BCL-2 in CLL)
6. Impaired Differentiation: Failure of myeloid or lymphoid maturation ("differentiation block")

Exam Detail: ### Molecular Pathophysiology by Subtype

Acute Myeloid Leukaemia (AML)

AML is characterised by clonal expansion of myeloid blasts (≥20% in bone marrow or blood) with impaired differentiation. The WHO 2022 classification emphasises recurrent genetic abnormalities and molecular markers. [9]

Major Genetic Categories:

1. AML with Recurrent Genetic Abnormalities:

   • t(8;21)(q22;q22); RUNX1-RUNX1T1: Accounts for 5-10% of AML; associated with favourable prognosis; often presents with granulocytic sarcomas
   • inv(16)(p13.1q22) or t(16;16); CBFB-MYH11: Core-binding factor AML; favourable prognosis; associated with abnormal eosinophils
   • t(15;17)(q24;q21); PML-RARA: Acute promyelocytic leukaemia (APL); unique management with ATRA + ATO
   • t(9;11)(p21.3;q23.3); MLLT3-KMT2A: MLL-rearranged AML; intermediate prognosis
   • t(6;9)(p23;q34.1); DEK-NUP214: Poor prognosis; basophilia
   • inv(3)(q21.3q26.2) or t(3;3); GATA2-MECOM: Very poor prognosis

2. AML with Gene Mutations:

   • NPM1-mutated AML (30% of AML): Favourable prognosis if FLT3-ITD absent; cytoplasmic NPM1 on immunohistochemistry
   • CEBPA-mutated AML: Biallelic mutations confer favourable prognosis
   • TP53-mutated AML: Very poor prognosis; often therapy-related or secondary

3. AML with Myelodysplasia-Related Changes: Prior MDS history, MDS-related cytogenetics, or multilineage dysplasia; poorer prognosis

4. FLT3-ITD Mutations (25-30% of AML): Internal tandem duplications in FLT3 gene cause constitutive tyrosine kinase activity; adverse prognostic marker; targetable with FLT3 inhibitors (midostaurin, gilteritinib). High FLT3-ITD allelic ratio (> 0.5) particularly unfavourable. [10]

5. IDH1/IDH2 Mutations (15-20% of AML): Produce oncometabolite 2-hydroxyglutarate causing epigenetic dysregulation; targetable with IDH inhibitors (ivosidenib, enasidenib)

Pathophysiological Consequences:

• Bone marrow infiltration → cytopenias (anaemia, thrombocytopenia, neutropenia)
• Extramedullary disease → chloromas (myeloid sarcomas), gum hypertrophy (monocytic AML), CNS involvement
• Leukostasis (WCC > 100 × 10⁹/L) → microvascular occlusion causing stroke, pulmonary infiltrates, priapism
• Coagulopathy → DIC (especially APL due to release of procoagulants from promyelocyte granules)

Acute Lymphoblastic Leukaemia (ALL)

ALL results from clonal proliferation of lymphoid progenitors (B-cell or T-cell lineage) with maturation arrest. Adult ALL differs significantly from paediatric ALL in molecular profile and prognosis. [11]

B-cell ALL (85% of adult ALL):

1. Philadelphia chromosome-positive (Ph+) ALL (25-30% adult ALL):

   • t(9;22)(q34;q11); BCR-ABL1 fusion
   • Creates constitutively active tyrosine kinase
   • Historically poor prognosis; transformed by TKI therapy
   • Multiple BCR-ABL1 isoforms: p190 (common in ALL), p210 (common in CML)

2. BCR-ABL1-like ALL (15-20% adult ALL):

   • Gene expression signature similar to Ph+ ALL but lacks BCR-ABL1
   • Alterations in kinase signalling (CRLF2, JAK2, ABL1/2, PDGFRB)
   • Poor prognosis; potential targets for TKI or JAK inhibitors

3. Hyperdiploid ALL (> 50 chromosomes):

   • More common in children; favourable prognosis
   • Rare in adults

4. KMT2A (MLL) rearrangements (5-10% adult ALL):

   • t(4;11), t(11;19), others
   • Poor prognosis; associated with infants and secondary leukaemia

5. ETV6-RUNX1 (rare in adults):

   • Favourable in children; very uncommon in adults

T-cell ALL (15% of adult ALL):

• Often associated with mediastinal mass (thymic involvement)
• Higher CNS involvement risk
• NOTCH1 mutations common (50-60%)
• Early T-cell precursor (ETP) ALL subtype has very poor prognosis

Pathophysiological Consequences:

• Bone marrow failure → pancytopenia
• Lymphadenopathy and hepatosplenomegaly → lymphoid infiltration
• CNS involvement (5-10% at diagnosis) → meningeal leukaemia, cranial nerve palsies
• Mediastinal mass (T-ALL) → SVC obstruction, respiratory compromise
• Testicular involvement → sanctuary site for relapse

Chronic Myeloid Leukaemia (CML)

CML is defined by the presence of the Philadelphia chromosome [t(9;22)(q34;q11)], resulting in the BCR-ABL1 fusion oncogene. This encodes a constitutively active tyrosine kinase that drives uncontrolled myeloid proliferation. [12]

Molecular Mechanism:

• BCR-ABL1 activates multiple signalling pathways: RAS/MAPK, PI3K/AKT, JAK/STAT
• Promotes proliferation and inhibits apoptosis
• Impairs DNA repair, increasing genomic instability
• Over time, additional mutations accumulate (TP53, RUNX1, ASXL1), driving disease progression

Clinical Phases:

1. Chronic Phase (CP-CML) (85% at diagnosis):

   • Well-differentiated myeloid cells
   • Blasts less than 10% in blood and bone marrow
   • Asymptomatic or mild symptoms
   • Excellent response to TKI therapy

2. Accelerated Phase (AP-CML):

   • Blasts 10-19%
   • Basophils ≥20%
   • Persistent thrombocytopenia or thrombocytosis
   • Progressive splenomegaly
   • Clonal evolution (additional cytogenetic abnormalities)

3. Blast Crisis (BC-CML):

   • Blasts ≥20% (essentially acute leukaemia)
   • Extramedullary blastic infiltration
   • Myeloid blast crisis (70%), lymphoid blast crisis (30%)
   • Very poor prognosis despite therapy

TKI Resistance Mechanisms:

• BCR-ABL1 kinase domain mutations (especially T315I "gatekeeper" mutation)
• BCR-ABL1 amplification
• Activation of alternative signalling pathways
• Clonal evolution

Chronic Lymphocytic Leukaemia (CLL)

CLL is characterised by accumulation of mature but dysfunctional B lymphocytes in blood, bone marrow, lymph nodes, and spleen. Unlike acute leukaemias, CLL cells have a proliferative defect and primarily accumulate due to resistance to apoptosis. [13]

Molecular Pathogenesis:

1. BCL-2 Overexpression: Anti-apoptotic protein prevents programmed cell death; target for venetoclax

2. Immunoglobulin Heavy Chain Variable Region (IGHV) Mutation Status:

   • Unmutated IGHV (≥98% homology to germline): Poor prognosis, median survival 8-10 years
   • Mutated IGHV (less than 98% homology): Favourable prognosis, median survival 20-25 years
   • Reflects different cells of origin and disease biology

3. Chromosomal Abnormalities (FISH):

   • del(13q) (50%): Most common; favourable prognosis
   • Trisomy 12 (15%): Intermediate prognosis; atypical morphology
   • del(11q) (ATM deletion, 15%): Poor prognosis; bulky lymphadenopathy
   • del(17p) (TP53 deletion, 5-10%): Worst prognosis; chemo-refractoriness; requires novel agents

4. TP53 Mutations: Present in 5-10%; predict poor response to chemoimmunotherapy; mandate use of BCR pathway or BCL-2 inhibitors

5. NOTCH1, SF3B1, BIRC3 Mutations: Associated with adverse outcomes and disease progression

Key Pathophysiological Features:

• Immune dysfunction: Hypogammaglobulinaemia (recurrent infections), autoimmune phenomena (AIHA, ITP)
• Bone marrow infiltration: Progressive cytopenias
• Lymphadenopathy and organomegaly: Lymphoid tissue infiltration
• Richter transformation (2-10%): Transformation to aggressive diffuse large B-cell lymphoma (DLBCL); median survival 6-12 months

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4. Clinical Presentation

Symptoms

The clinical presentation varies dramatically between acute and chronic leukaemias, reflecting their different disease biology and tempo.

Acute Leukaemias (AML, ALL)

Acute leukaemias typically present with symptoms of bone marrow failure and tissue infiltration, evolving over days to weeks:

Bone Marrow Failure Syndrome:

• Anaemia (fatigue, dyspnoea, pallor, tachycardia) – present in 80-90%
• Thrombocytopenia (bleeding, bruising, petechiae, mucosal bleeding) – 70-80%
• Neutropenia (fever, recurrent infections, mouth ulcers) – 50-60%

Systemic Symptoms:

• Fever (60-70%) – may indicate infection or disease itself
• Night sweats (30-40%)
• Weight loss (30-50%)
• Bone pain (20-30%) – due to marrow expansion; more common in ALL
• Fatigue and malaise (> 80%)

Tissue Infiltration:

• Lymphadenopathy (40-60% in ALL, 10-20% in AML)
• Hepatosplenomegaly (30-50%)
• Gum hypertrophy (10-15% in monocytic AML – M4/M5 subtypes)
• Skin infiltration (5-10%) – leukaemia cutis
• Testicular swelling (ALL)

CNS Involvement (5-10% at diagnosis in ALL, rare in AML):

• Headache, vomiting, visual disturbance
• Cranial nerve palsies
• Meningism

Hyperleukocytosis Syndrome (WCC > 100 × 10⁹/L):

• Respiratory distress (pulmonary leukostasis)
• Neurological symptoms (confusion, visual changes, stroke)
• Priapism
• Requires urgent leukapheresis and chemotherapy

Chronic Leukaemias (CML, CLL)

Chronic leukaemias have indolent onset, often asymptomatic at diagnosis (40-50% discovered incidentally on routine blood tests).

CML Presentation:

Chronic Phase (85% at diagnosis):

• Asymptomatic (30-40%) – incidental finding on FBC
• Fatigue (50-60%)
• Weight loss and night sweats (30-40%)
• Early satiety and abdominal fullness (40-50%) – due to splenomegaly
• Left upper quadrant pain (20-30%) – splenic infarction
• Gout/hyperuricaemia (10-15%) – high cell turnover
• Hyperviscosity symptoms (rare) – if very high WCC

Accelerated Phase/Blast Crisis:

• Progressive symptoms
• Worsening cytopenias
• Fever, bone pain
• Extramedullary disease (chloromas, CNS)

CLL Presentation:

• Asymptomatic (50-80%) – incidental lymphocytosis
• Lymphadenopathy (50-70%) – painless, generalised
• Fatigue (30-50%)
• Recurrent infections (25-40%) – hypogammaglobulinaemia
• Early satiety (20-30%) – splenomegaly
• Autoimmune phenomena (10-20%):
  • Autoimmune haemolytic anaemia (AIHA)
  • Immune thrombocytopenia (ITP)
  • Pure red cell aplasia

Signs

Red Flags and Emergencies

[!CAUTION] ONCOLOGICAL EMERGENCIES:

1. Neutropenic Sepsis (Febrile Neutropenia)
   • Temperature ≥38°C with neutrophils less than 0.5 × 10⁹/L
   • Medical emergency: mortality 10-20% without prompt antibiotics
   • Immediate broad-spectrum antibiotics (e.g., piperacillin-tazobactam)
   • Blood cultures, but DO NOT delay antibiotics
2. Tumour Lysis Syndrome (TLS)
   • Massive cell death releases intracellular contents
   • Hyperuricaemia, hyperkalaemia, hyperphosphataemia, hypocalcaemia
   • Acute kidney injury, arrhythmias, seizures
   • Prophylaxis: IV hydration, allopurinol/rasburicase
   • Monitor: U&Es, Ca, PO₄, urate, LDH 4-6 hourly
3. Disseminated Intravascular Coagulation (DIC)
   • Especially APL (APML, M3 subtype)
   • Bleeding + thrombosis
   • Prolonged PT/APTT, low fibrinogen, elevated D-dimer
   • Immediate ATRA initiation (even before confirmation)
   • Supportive: FFP, cryoprecipitate, platelet transfusion
4. Hyperleukocytosis (WCC > 100 × 10⁹/L)
   • Leukostasis: microvascular occlusion
   • CNS: confusion, stroke, visual changes
   • Respiratory: dyspnoea, hypoxia, infiltrates on CXR
   • Urgent cytoreduction: leukapheresis + chemotherapy
   • Avoid RBC transfusion (increases viscosity)
5. Superior Vena Cava Obstruction (SVCO)
   • T-ALL with anterior mediastinal mass
   • Facial swelling, dyspnoea, dilated chest wall veins
   • Urgent steroids + chemotherapy
   • Avoid GA/sedation (airway compromise)
6. CNS Leukaemia
   • Headache, vomiting, cranial nerve palsies
   • Raised ICP, seizures
   • LP (if safe: no raised ICP, platelets > 40 × 10⁹/L)
   • Intrathecal chemotherapy
7. Blast Crisis in CML
   • Transformation to acute leukaemia
   • Rapid clinical deterioration
   • Poor prognosis despite therapy
   • Urgent haematology referral

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5. Differential Diagnosis

Leukaemia must be distinguished from other causes of cytopenias, lymphocytosis, or constitutional symptoms.

Differential Diagnoses by Presentation

For Pancytopenia/Cytopenias

For Lymphocytosis

For Leucocytosis/High WCC

For B Symptoms (Fever, Night Sweats, Weight Loss)

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6. Investigations

Initial Investigations

The diagnostic approach follows a systematic pathway from screening blood tests to definitive bone marrow examination.

Full Blood Count (FBC) with Differential

Pathognomonic Findings:

• WCC: Markedly elevated (> 50 × 10⁹/L in many cases) or low
• Haemoglobin: Low (anaemia in 70-90%)
• Platelets: Low (less than 100 × 10⁹/L in 60-80%)
• Blast cells in peripheral blood (acute leukaemias)

Subtype Patterns:

Blood Film

Essential for morphological assessment:

AML:

• Myeloblasts: Large cells, high nucleus:cytoplasm ratio, nucleoli, fine chromatin
• Auer rods: Crystalline azurophilic granules (pathognomonic for AML)
• Monocytic features (M4/M5): Large nuclei, abundant cytoplasm

APL (M3):

• Abnormal promyelocytes with heavy azurophilic granulation
• Faggot cells: bundles of Auer rods
• Bilobed nuclei

ALL:

• Lymphoblasts: Small to medium size, scant cytoplasm, indistinct nucleoli
• High nucleus:cytoplasm ratio

CML:

• Left shift: Entire myeloid maturation spectrum (blasts → neutrophils)
• Basophilia: Characteristic feature
• Eosinophilia

CLL:

• Mature small lymphocytes: Clumped chromatin
• Smudge cells (smear cells): Fragile lymphocytes disrupted during film preparation (pathognomonic)

Coagulation Screen

• PT, APTT, fibrinogen, D-dimer: Essential in acute leukaemias
• DIC: Especially in APL (prolonged PT/APTT, low fibrinogen, ↑ D-dimer)

Biochemistry

• Urate: Elevated (high cell turnover); risk of tumour lysis syndrome
• LDH: Elevated (marker of cell turnover and disease burden)
• Urea, creatinine, electrolytes: Baseline renal function; TLS monitoring
• Calcium, phosphate: TLS monitoring
• Liver function tests: Hepatic infiltration, baseline for chemotherapy

Definitive Diagnostic Investigations

Bone Marrow Aspiration and Trephine Biopsy

Indications: All suspected leukaemias

Findings:

Note: WHO 2022 classification defines acute leukaemia as ≥20% blasts in bone marrow or blood (exception: APL and core-binding factor AML diagnosed regardless of blast count if characteristic genetic abnormality present).

Immunophenotyping (Flow Cytometry)

Determines cell lineage (myeloid vs lymphoid) and maturation stage; essential for classification.

AML Markers:

• Myeloid: CD13, CD33, CD117, MPO (myeloperoxidase)
• Monocytic: CD14, CD64

ALL Markers:

• B-cell: CD10, CD19, CD20, CD22, CD79a
  • "Pre-B ALL: CD10⁺ (CALLA positive)"
  • "Mature B-ALL: Surface immunoglobulin⁺"
• T-cell: CD1a, CD2, CD3, CD4, CD5, CD7, CD8

CLL Immunophenotype (diagnostic):

• CD5⁺ CD23⁺ B cells (aberrant co-expression)
• CD19⁺ CD20^dim^
• Clonal light chain restriction (κ or λ)
• Score ≥4 on Matutes score (CD5, CD23, FMC7, sIg, CD79b)

Cytogenetics (Karyotyping)

Identifies chromosomal abnormalities; critical for diagnosis, prognosis, and treatment selection.

Key Abnormalities:

Molecular Genetics

Identifies gene mutations; essential for risk stratification and targeted therapy.

AML:

• FLT3-ITD and FLT3-TKD: Risk stratification; FLT3 inhibitor therapy
• NPM1: Favourable if FLT3-ITD negative
• CEBPA: Biallelic mutations favourable
• IDH1/IDH2: IDH inhibitor therapy (ivosidenib, enasidenib)
• TP53: Very poor prognosis

ALL:

• BCR-ABL1 (PCR): Confirms Ph⁺ ALL; TKI therapy
• BCR-ABL1-like signature: Consider kinase inhibitors

CML:

• BCR-ABL1 (quantitative PCR): Diagnostic; monitors treatment response
• BCR-ABL1 kinase domain mutations: Detects TKI resistance (e.g., T315I)

CLL:

• IGHV mutation status: Prognostic (unmutated = poor prognosis)
• TP53 mutation/del(17p): Mandates novel agents
• NOTCH1, SF3B1, BIRC3: Adverse prognostic markers

FISH (Fluorescence In Situ Hybridisation)

Faster than karyotyping; detects specific abnormalities even in non-dividing cells.

CLL FISH Panel (standard):

• del(13q), del(11q), del(17p), trisomy 12

CML:

• BCR-ABL1 fusion

ALL:

• BCR-ABL1, MLL rearrangements, TEL-AML1

Staging and Risk Stratification

CLL Staging

Binet Staging (Europe):

Lymphoid areas: cervical, axillary, inguinal LNs (bilateral = 1 area each); liver; spleen

Rai Staging (USA):

AML Risk Stratification (ELN 2022)

Based on cytogenetics and molecular genetics; guides treatment intensity and transplant decisions.

Imaging

CT Chest/Abdomen/Pelvis:

• Lymphadenopathy (ALL, CLL)
• Organomegaly
• Mediastinal mass (T-ALL)
• Extramedullary disease

PET-CT:

• Richter transformation (CLL → DLBCL)
• Lymphoma staging

Lumbar Puncture (CNS Assessment)

Indications:

• ALL (high risk): WCC > 30 × 10⁹/L, T-cell phenotype, mature B-ALL
• CNS symptoms
• Testicular involvement

Requirements:

• Platelets > 40 × 10⁹/L (transfuse if necessary)
• No raised ICP

CSF Analysis:

• Cell count and cytospin (blasts?)
• Biochemistry

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7. Management

The treatment of leukaemia is highly subtype-specific, ranging from immediate intensive chemotherapy (acute leukaemias) to prolonged observation (many CLL patients). Modern management incorporates molecular risk stratification, targeted therapies, and allogeneic stem cell transplantation.

General Principles

1. Confirm diagnosis urgently: Bone marrow examination within 24-48 hours
2. Risk assessment: Cytogenetics and molecular genetics
3. Supportive care: Blood product support, infection prophylaxis
4. MDT discussion: Haematology, oncology, transplant teams
5. Clinical trial consideration: Where available

Supportive Care (All Leukaemias)

Blood Product Support

Note: Irradiated blood products required (prevent transfusion-associated GVHD in immunocompromised patients)

Caution: Avoid RBC transfusion in hyperleukocytosis (increases viscosity)

Infection Prophylaxis and Management

• Neutropenic sepsis protocol: Immediate broad-spectrum antibiotics (piperacillin-tazobactam or meropenem)
• G-CSF: Consider if prolonged neutropenia expected
• Antimicrobial prophylaxis:
  • "Antibacterial: Fluoroquinolone (ciprofloxacin, levofloxacin)"
  • "Antifungal: Fluconazole or posaconazole"
  • "Antiviral: Aciclovir (HSV/VZV prophylaxis)"
  • "PCP prophylaxis: Co-trimoxazole (especially ALL, high-dose steroids)"

Tumour Lysis Syndrome (TLS) Prophylaxis

High-risk patients (high WCC, bulky disease, high LDH):

• IV hydration: 3 L/day minimum
• Allopurinol: 300-600 mg/day (xanthine oxidase inhibitor)
• Rasburicase: Recombinant urate oxidase (if very high urate or renal impairment)
• Monitor: U&Es, Ca, PO₄, urate, LDH every 4-6 hours initially

Avoid:

• Potassium supplementation
• Loop diuretics (unless fluid overload)

Acute Myeloid Leukaemia (AML)

Induction Chemotherapy (Aim: Achieve Complete Remission)

Standard "7+3" Regimen (fit patients less than 60-65 years):

• Cytarabine (ara-C): 100-200 mg/m² IV continuous infusion for 7 days
• Anthracycline (daunorubicin or idarubicin): 3 days
  • Daunorubicin 60-90 mg/m² IV days 1-3
  • Idarubicin 12 mg/m² IV days 1-3

Outcomes:

• Complete remission (CR): 60-80% in younger patients (less than 60 years)
• CR: 40-60% in older patients (> 60 years)

Older/Unfit Patients:

• Hypomethylating agents (HMA): Azacitidine or decitabine
• Venetoclax + HMA: Combination approved; improved CR rates (60-70% vs 20-30% HMA alone)
• Low-dose cytarabine (LDAC): 20 mg SC twice daily for 10 days

Targeted Therapies:

Consolidation Chemotherapy (Post-Remission Therapy)

High-dose cytarabine (HiDAC):

• Cytarabine 3 g/m² IV over 3 hours every 12 hours on days 1, 3, 5 (total 6 doses)
• Typically 3-4 cycles
• Reduces relapse risk

Allogeneic Stem Cell Transplantation (Allo-SCT):

Indications:

• Intermediate or adverse-risk AML in CR1 (first complete remission)
• Favourable-risk AML: Only if relapse or no CR with first-line therapy
• Relapsed/refractory AML: If CR achieved

Requirements:

• Fit patient (less than 70 years typically; up to 75 with RIC conditioning)
• HLA-matched donor (sibling or unrelated)
• Disease control (CR or minimal disease)

Outcomes:

• 5-year survival post-transplant: 40-60% (depends on risk category, donor type)
• Graft-versus-leukaemia (GvL) effect: Allogeneic immune cells attack residual leukaemia

Acute Promyelocytic Leukaemia (APL) – Unique Management

APL is a medical emergency with high early mortality from DIC but is highly curable (85-90% cure rate).

Immediate Treatment (start even before confirmation):

• ATRA (all-trans retinoic acid): 45 mg/m² PO daily in divided doses

  • Induces differentiation of promyelocytes
  • Reduces DIC risk
  • Continue until molecular remission

• Arsenic trioxide (ATO): 0.15 mg/kg IV daily

  • Induces apoptosis
  • Synergistic with ATRA

ATRA + ATO Regimen (now standard for non-high-risk APL):

• Induction: ATRA + ATO until CR
• Consolidation: ATRA + ATO cycles
• Outcomes: 90-95% molecular remission, 85-90% cure rate
• No chemotherapy required (unless high-risk: WCC > 10 × 10⁹/L)

High-risk APL (WCC > 10 × 10⁹/L at presentation):

• Add idarubicin to ATRA + ATO

Complications:

• DIC: Supportive care (FFP, cryoprecipitate, platelets)
• Differentiation syndrome (ATRA/ATO syndrome): Fever, dyspnoea, pulmonary infiltrates, pleural effusion; treat with dexamethasone 10 mg IV BD immediately
• QTc prolongation with ATO: Monitor ECG; correct electrolytes

Monitoring:

• Minimal residual disease (MRD) by PCR for PML-RARA: Every 3 months post-treatment
• Molecular relapse: Detectable PML-RARA transcript

Acute Lymphoblastic Leukaemia (ALL)

ALL requires intensive multi-agent chemotherapy with CNS prophylaxis over 2-3 years.

Phases of Treatment

1. Induction (Aim: CR, typically 4-6 weeks)

Multi-agent regimen:

• Vincristine
• Corticosteroids (dexamethasone or prednisolone)
• Asparaginase (PEGylated)
• Anthracycline (daunorubicin)
• Intrathecal chemotherapy (methotrexate ± cytarabine ± hydrocortisone) – CNS prophylaxis

Philadelphia-positive ALL (Ph⁺ ALL):

• Add TKI (imatinib, dasatinib, or ponatinib) to chemotherapy
• Dramatically improves outcomes (CR rates > 90%)

Outcomes:

• CR rate: 85-90% (adults)
• Higher in children (> 95%)

2. Consolidation (Intensification)

High-dose chemotherapy cycles (e.g., high-dose methotrexate, high-dose cytarabine)

3. CNS Prophylaxis

• Intrathecal chemotherapy: Regular throughout treatment
• Cranial radiotherapy: Reserved for CNS-positive disease or very high-risk patients (due to neurotoxicity)

4. Maintenance (2-3 years)

• Mercaptopurine (6-MP) daily
• Methotrexate weekly
• Vincristine and steroids pulses monthly
• Intrathecal chemotherapy every 3 months

Allogeneic Stem Cell Transplantation:

Indications:

• Ph⁺ ALL in CR1 (debate ongoing with excellent TKI results)
• High-risk ALL (Ph-like ALL, hypodiploidy, poor early response, MRD-positive)
• Relapsed ALL in CR2

Novel Therapies (Relapsed/Refractory ALL)

CAR-T cell therapy has shown remarkable responses (80-90% CR) in relapsed/refractory ALL, though with significant toxicities (cytokine release syndrome, neurotoxicity).

Chronic Myeloid Leukaemia (CML)

CML management has been revolutionised by TKI therapy, transforming a fatal disease to a chronic condition with near-normal life expectancy.

First-Line Treatment: TKI Therapy

TKI Options (all target BCR-ABL1 tyrosine kinase):

Initial Choice:

• Imatinib: Standard first-line (cost-effective, long-term safety data)
• 2nd-generation TKIs (dasatinib, nilotinib): May be preferred for faster/deeper responses or high-risk patients

Monitoring Treatment Response

BCR-ABL1 Quantitative PCR (international scale, IS):

Responses Defined:

• Complete haematological response (CHR): Normal FBC, no splenomegaly
• Complete cytogenetic response (CCyR): 0% Ph⁺ metaphases on karyotype
• Major molecular response (MMR): BCR-ABL1 ≤0.1% IS (3-log reduction)
• MR4.5 (deep molecular response): BCR-ABL1 ≤0.0032% IS (4.5-log reduction)

TKI Resistance

Causes:

• BCR-ABL1 kinase domain mutations (especially T315I)
• BCR-ABL1 amplification
• Poor compliance

Management:

• Switch to alternative TKI:
  • If imatinib failure → dasatinib or nilotinib
  • If 2nd-generation TKI failure → ponatinib (especially T315I)
• Mutation testing (BCR-ABL1 kinase domain sequencing)
• Allogeneic SCT: Consider if multiple TKI failures or blast crisis

Treatment-Free Remission (TFR)

Patients achieving sustained deep molecular response (MR4.5 for ≥2 years) may attempt TKI discontinuation under close monitoring:

• 50-60% remain in remission off therapy
• Molecular recurrence usually occurs within 6 months
• Restart TKI if loss of MMR
• Safe strategy with monthly monitoring

Management of Blast Crisis

• Restart/escalate TKI (ponatinib if T315I)
• Chemotherapy (AML or ALL regimens depending on phenotype)
• Allogeneic SCT if CR achieved (only potentially curative option)
• Prognosis: Poor (median survival 6-12 months)

Chronic Lymphocytic Leukaemia (CLL)

CLL has a highly variable course. Many patients never require treatment ("watch and wait"), while others progress rapidly and need intensive therapy.

Indications for Treatment (Initiate When Symptomatic or Progressive)

International Workshop on CLL (iwCLL) Criteria:

• Progressive bone marrow failure: Worsening anaemia (Hb less than 100 g/L) or thrombocytopenia (platelets less than 100 × 10⁹/L)
• Massive or progressive lymphadenopathy (> 10 cm or increasing > 50% in 2 months)
• Massive or progressive splenomegaly (> 6 cm below costal margin or increasing > 50% in 2 months)
• Progressive lymphocytosis: > 50% increase over 2 months or lymphocyte doubling time less than 6 months
• Autoimmune cytopenias refractory to steroids
• Constitutional symptoms: Unintentional weight loss > 10% in 6 months, fevers > 38°C for ≥2 weeks, night sweats > 1 month

Watch and Wait:

• Asymptomatic, stable disease (Binet A/B, Rai 0-II)
• 30-50% of CLL patients never require treatment
• Monitor: FBC, clinical examination every 3-6 months

First-Line Treatment

1. TP53-disrupted CLL (del(17p) or TP53 mutation) – AVOID CHEMOIMMUNOTHERAPY:

2. Fit Patients, TP53 Wild-Type:

IGHV-mutated (favourable):

• FCR (fludarabine, cyclophosphamide, rituximab): Traditional chemoimmunotherapy; high cure rates in young, fit patients with mutated IGHV
• Venetoclax + obinutuzumab: Increasingly preferred (fixed duration, high MRD negativity)

IGHV-unmutated (unfavourable):

• Venetoclax + obinutuzumab: Preferred
• Ibrutinib/acalabrutinib ± obinutuzumab: Alternative

3. Unfit/Elderly Patients:

• Venetoclax + obinutuzumab: Preferred (fixed duration)
• Ibrutinib: Continuous therapy
• Chlorambucil + obinutuzumab: If unable to tolerate intensive regimens

Relapsed/Refractory CLL

Options:

• Alternative BTK inhibitor (if relapsed on ibrutinib → acalabrutinib; or vice versa)
• Venetoclax (if not used first-line)
• PI3K inhibitors (idelalisib, duvelisib): Reserved for relapsed disease; significant toxicities
• Allogeneic SCT: Consider in young, fit patients with refractory disease or multiple relapses

Richter Transformation (CLL → DLBCL)

• Occurs in 2-10% of CLL patients
• Suspect if: Rapid lymph node enlargement, B symptoms, elevated LDH
• Diagnosis: Lymph node biopsy (PET-CT to identify active node)
• Treatment: R-CHOP or clinical trial
• Prognosis: Poor (median survival 6-12 months)

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8. Complications

Acute Complications

Treatment-Related Complications

Transplant-Related Complications

Late Complications

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9. Prognosis

Prognosis varies enormously by leukaemia subtype, molecular profile, age, and treatment response.

Acute Myeloid Leukaemia (AML)

Overall 5-year Survival:

• Younger patients (less than 60 years): 40-50%
• Older patients (> 60 years): 10-20%

By Risk Category (ELN 2022):

Acute Promyelocytic Leukaemia (APL):

• Cure rate: 85-90% with ATRA + ATO (remarkable for an acute leukaemia)
• Early mortality: 10-15% (from DIC/bleeding)
• Long-term molecular remission: 90%

Prognostic Factors:

Acute Lymphoblastic Leukaemia (ALL)

Overall 5-year Survival:

• Children: 90% (one of paediatric oncology's great successes)
• Adolescents/Young Adults (15-39 years): 60-70%
• Older Adults (> 60 years): 20-30%

By Subtype:

Prognostic Factors:

Chronic Myeloid Leukaemia (CML)

With TKI Therapy:

• Overall survival: Near-normal life expectancy (approaching age-matched controls)
• 10-year survival: 80-90%
• Transformation to blast crisis: less than 5% with optimal TKI therapy (was 10-20% per year historically)

Sokal Score (prognostic at diagnosis):

• Low risk (40%): 10-year survival 95%
• Intermediate risk (40%): 10-year survival 85%
• High risk (20%): 10-year survival 75%

Blast Crisis:

• Median survival: 6-12 months (very poor despite therapy)

Chronic Lymphocytic Leukaemia (CLL)

Overall 5-year Survival: 70-80% (highly variable)

By Binet Stage:

By Molecular Risk:

Richter Transformation: Median survival 6-12 months

With Novel Agents (venetoclax, BTK inhibitors):

• Outcomes significantly improved, even in high-risk disease
• Treatment-free intervals extended
• Overall survival improving (long-term data awaited)

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10. Prevention & Screening

Primary Prevention

Modifiable Risk Factors:

• Smoking cessation: Reduces AML risk by 30-50%
• Occupational safety: Minimize benzene exposure (chemical industry, petroleum workers)
• Limit ionising radiation: Appropriate use of medical imaging

Genetic Counselling:

• Familial CLL (first-degree relatives have 2-7× risk)
• Inherited cancer syndromes (Li-Fraumeni, Fanconi anaemia)

Screening

No population-based screening exists for leukaemia (low incidence, no validated screening test).

High-Risk Surveillance:

• Prior chemotherapy (alkylating agents, topoisomerase II inhibitors): Annual FBC
• Genetic predisposition syndromes: Specialist haematology follow-up
• Antecedent haematological disorders (MDS, MPN): 3-6 monthly FBC, bone marrow surveillance

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11. Key Guidelines

International Guidelines

1. National Comprehensive Cancer Network (NCCN)

   • AML Guidelines (2025)
   • ALL Guidelines (2025)
   • CML Guidelines (2025)
   • CLL/SLL Guidelines (2025)
   • Evidence-based, updated annually

2. European LeukemiaNet (ELN)

   • AML Risk Stratification and Management (2022)
   • CML Management Recommendations (2020)
   • Standardises molecular monitoring and response criteria

3. British Society for Haematology (BSH)

   • Guidelines for AML (2023)
   • Guidelines for ALL (2021)
   • Guidelines for CML (2022)
   • Guidelines for CLL (2022)

4. European Society for Medical Oncology (ESMO)

   • Clinical Practice Guidelines for Leukaemias (updated regularly)

Key Recommendations Summary

AML:

• Induction: "7+3" (cytarabine + anthracycline) for fit patients; HMA + venetoclax for unfit
• Consolidation: High-dose cytarabine ± allogeneic SCT (risk-dependent)
• APL: ATRA + ATO (no chemotherapy for low/intermediate risk)
• FLT3-ITD: Add midostaurin to induction/consolidation

ALL:

• Multi-agent chemotherapy over 2-3 years
• CNS prophylaxis mandatory (intrathecal chemotherapy ± cranial RT)
• Ph⁺ ALL: TKI + chemotherapy; consider transplant in CR1

CML:

• First-line: TKI (imatinib or 2nd-generation TKI)
• Monitoring: BCR-ABL1 PCR every 3 months initially
• TKI switch: If suboptimal response or resistance
• TFR: Consider discontinuation if sustained MR4.5 for ≥2 years

CLL:

• Watch and wait for asymptomatic, stable disease
• First-line (TP53-disrupted): BTK inhibitor or venetoclax + obinutuzumab
• First-line (TP53 wild-type, fit, IGHV-mutated): FCR or venetoclax + obinutuzumab
• First-line (unfit): Venetoclax + obinutuzumab or ibrutinib

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12. Common Exam Questions

Viva/Oral Examination Questions

1. "Describe the classification of leukaemia."

   • Classify by lineage (myeloid vs lymphoid) and tempo (acute vs chronic)
   • Four main types: AML, ALL, CML, CLL
   • Mention WHO 2022 classification for AML/ALL (genetic abnormalities)

2. "A 65-year-old presents with fatigue, bruising, and WCC 2.5 × 10⁹/L. Blood film shows 40% blasts with Auer rods. What is the diagnosis and immediate management?"

   • Diagnosis: AML (blasts ≥20%, Auer rods pathognomonic)
   • Immediate: FBC, coagulation (DIC?), bone marrow biopsy, cytogenetics/molecular
   • Supportive: Blood products, antibiotics if febrile
   • Specific: Urgent haematology referral, induction chemotherapy (7+3)
   • If APL suspected (promyelocytes, DIC): Start ATRA immediately

3. "What is the Philadelphia chromosome, and what is its significance?"

   • t(9;22)(q34;q11) translocation → BCR-ABL1 fusion oncogene
   • Defines CML (100% of cases)
   • Present in 25-30% adult ALL (Ph⁺ ALL)
   • Creates constitutively active tyrosine kinase
   • Therapeutic significance: Target for TKI therapy (imatinib, dasatinib, nilotinib, ponatinib)
   • Transformed CML prognosis (5-year survival from 20% → 90%)

4. "How would you manage a patient with CLL, Binet stage A, asymptomatic?"

   • Watch and wait (no treatment indicated)
   • Explain: Many CLL patients never require treatment
   • Monitoring: FBC and clinical examination every 3-6 months
   • Initiate treatment if: Progressive cytopenias, symptomatic lymphadenopathy/splenomegaly, constitutional symptoms, autoimmune complications
   • Check TP53 status and IGHV mutation for prognostication

5. "What are the complications of tumour lysis syndrome, and how do you prevent it?"

   • Complications: Hyperuricaemia → AKI; hyperkalaemia → arrhythmias; hyperphosphataemia + hypocalcaemia → seizures
   • Prevention:
     • IV hydration (3 L/day minimum)
     • Allopurinol 300-600 mg/day (or rasburicase if high-risk)
     • Monitor U&Es, Ca, PO₄, urate, LDH 4-6 hourly
     • Avoid potassium supplementation
   • High-risk patients: High WCC, bulky disease, elevated LDH, pre-existing renal impairment

SBA/MCQ High-Yield Topics

• Auer rods → AML (pathognomonic)
• Smudge cells → CLL
• t(15;17) PML-RARA → APL → ATRA + ATO
• t(9;22) BCR-ABL1 → CML → TKI therapy
• FLT3-ITD mutation → Adverse prognosis in AML → FLT3 inhibitor
• del(17p)/TP53 mutation in CLL → Avoid chemoimmunotherapy → BTK inhibitor or venetoclax
• Hyperleukocytosis → Leukostasis → Avoid RBC transfusion → Leukapheresis
• Neutropenic sepsis → Immediate broad-spectrum antibiotics → Piperacillin-tazobactam
• DIC in APL → Start ATRA immediately (even before confirmation)
• Philadelphia-positive ALL → Add TKI to chemotherapy

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13. Patient/Layperson Explanation

What is Leukaemia?

Leukaemia is a type of blood cancer that starts in the bone marrow, where blood cells are made. In leukaemia, the bone marrow produces too many abnormal white blood cells that don't work properly. These abnormal cells crowd out the normal blood cells, causing problems.

Types of Leukaemia

There are four main types of leukaemia:

1. Acute Leukaemias (develop quickly):

   • Acute Myeloid Leukaemia (AML): Most common acute leukaemia in adults
   • Acute Lymphoblastic Leukaemia (ALL): Most common cancer in children; less common in adults

2. Chronic Leukaemias (develop slowly):

   • Chronic Myeloid Leukaemia (CML): Usually affects middle-aged adults
   • Chronic Lymphocytic Leukaemia (CLL): Most common leukaemia overall; usually affects older adults

Symptoms

Symptoms depend on the type but may include:

• Feeling very tired and weak
• Getting infections easily
• Bruising or bleeding easily
• Pale skin
• Swollen glands (lymph nodes) in the neck, armpits, or groin
• Feeling full quickly (from an enlarged spleen)
• Fever and night sweats
• Weight loss

Acute leukaemias develop quickly over days to weeks and need urgent treatment.

Chronic leukaemias develop slowly and may not cause symptoms for years.

Diagnosis

Your doctor will:

• Take a blood sample (blood test)
• Look at the blood under a microscope
• Take a bone marrow sample (small needle into the hip bone)
• Do genetic tests to determine the exact type

Treatment

Treatment depends on the type of leukaemia:

Acute Leukaemias (AML, ALL):

• Chemotherapy: Strong medications to kill leukaemia cells
• Stem cell transplant: In some cases, to replace the bone marrow
• Targeted drugs: For certain genetic types

Chronic Leukaemias:

• CML: Tablet medications called tyrosine kinase inhibitors (TKIs) that target the leukaemia cells specifically. These have transformed CML from a fatal disease to a manageable condition.
• CLL: Many patients don't need treatment immediately ("watch and wait"). When treatment is needed, options include targeted drugs or chemotherapy.

Outlook

The outlook varies greatly by type:

• APL (a type of AML): 85-90% cure rate with modern treatment
• ALL in children: 90% cure rate
• CML: Near-normal life expectancy with TKI tablets
• CLL: Many patients live for 10-20 years or more

Your doctor will discuss your specific situation and prognosis with you.

Living with Leukaemia

• Attend all follow-up appointments
• Report fever or infections immediately (especially during chemotherapy)
• Avoid people with infections
• Eat a healthy diet
• Ask about vaccinations (some are safe; others are not during treatment)
• Seek support from family, friends, or support groups

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14. References

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2. Arber DA, Orazi A, Hasserjian R, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127(20):2391-2405. doi:10.1182/blood-2016-03-643544

3. Kantarjian H, O'Brien S, Jabbour E, et al. Improved survival in chronic myeloid leukemia since the introduction of imatinib therapy: a single-institution historical experience. Blood. 2012;119(9):1981-1987. doi:10.1182/blood-2011-08-358135

4. Lo-Coco F, Avvisati G, Vignetti M, et al. Retinoic acid and arsenic trioxide for acute promyelocytic leukemia. N Engl J Med. 2013;369(2):111-121. doi:10.1056/NEJMoa1300874

5. Tallman MS, Wang ES, Altman JK, et al. Acute Myeloid Leukemia, Version 3.2019, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2019;17(6):721-749. doi:10.6004/jnccn.2019.0028

6. Office for National Statistics. Cancer Registration Statistics, England: 2020. Available at: https://www.ons.gov.uk

7. Shallis RM, Wang R, Davidoff A, Ma X, Zeidan AM. Epidemiology of acute myeloid leukemia: Recent progress and enduring challenges. Blood Rev. 2019;36:70-87. doi:10.1016/j.blre.2019.04.005

8. Teras LR, DeSantis CE, Cerhan JR, Morton LM, Jemal A, Flowers CR. 2016 US lymphoid malignancy statistics by World Health Organization subtypes. CA Cancer J Clin. 2016;66(6):443-459. doi:10.3322/caac.21357

9. Döhner H, Wei AH, Appelbaum FR, et al. Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN. Blood. 2022;140(12):1345-1377. doi:10.1182/blood.2022016867

10. Stone RM, Mandrekar SJ, Sanford BL, et al. Midostaurin plus Chemotherapy for Acute Myeloid Leukemia with a FLT3 Mutation. N Engl J Med. 2017;377(5):454-464. doi:10.1056/NEJMoa1614359

11. Jabbour E, O'Brien S, Konopleva M, Kantarjian H. New insights into the pathophysiology and therapy of adult acute lymphoblastic leukemia. Cancer. 2015;121(15):2517-2528. doi:10.1002/cncr.29383

12. Hochhaus A, Baccarani M, Silver RT, et al. European LeukemiaNet 2020 recommendations for treating chronic myeloid leukemia. Leukemia. 2020;34(4):966-984. doi:10.1038/s41375-020-0776-2

13. Hallek M, Cheson BD, Catovsky D, et al. iwCLL guidelines for diagnosis, indications for treatment, response assessment, and supportive management of CLL. Blood. 2018;131(25):2745-2760. doi:10.1182/blood-2017-09-806398

14. Fischer K, Al-Sawaf O, Bahlo J, et al. Venetoclax and Obinutuzumab in Patients with CLL and Coexisting Conditions. N Engl J Med. 2019;380(23):2225-2236. doi:10.1056/NEJMoa1815281

15. Maude SL, Laetsch TW, Buechner J, et al. Tisagenlecleucel in Children and Young Adults with B-Cell Lymphoblastic Leukemia. N Engl J Med. 2018;378(5):439-448. doi:10.1056/NEJMoa1709866

16. Burnett AK, Russell NH, Hills RK, et al. Arsenic trioxide and all-trans retinoic acid treatment for acute promyelocytic leukaemia in all risk groups (AML17): results of a randomised, controlled, phase 3 trial. Lancet Oncol. 2015;16(13):1295-1305. doi:10.1016/S1470-2045(15)00193-X

17. Cortes JE, Kantarjian H, Shah NP, et al. Ponatinib in Refractory Philadelphia Chromosome-Positive Leukemias. N Engl J Med. 2012;367(22):2075-2088. doi:10.1056/NEJMoa1205127

18. Mahon FX, Réa D, Guilhot J, et al. Discontinuation of imatinib in patients with chronic myeloid leukaemia who have maintained complete molecular remission for at least 2 years: the prospective, multicentre Stop Imatinib (STIM) trial. Lancet Oncol. 2010;11(11):1029-1035. doi:10.1016/S1470-2045(10)70233-3

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Medical Disclaimer: This content is for educational purposes only and does not replace professional medical advice. Leukaemia requires specialist haematology care. Always consult a qualified healthcare provider for diagnosis and treatment decisions.