Chronic Myeloid Leukemia

Amer Rassam, M.D.

Learning Objectives

Myeloproliferative disorders (MPDs) Molecular genetics of chronic myeloid

leukemia Clinical manifestations and diagnosis of

chronic myeloid leukemia Overview of the treatment of chronic myeloid

leukemia Initial treatment of chronic myeloid leukemia in

chronic phase

Explain how to define and identify a relapse Treatment of CML in chronic phase after

failure of initial therapy Clinical use of tyrosine kinase inhibitors for

chronic myeloid leukemia Treatment of CML in accelerated phase and

blast crisis Prognosis

Learning Objectives

Myeloproliferative Disorders

Chronic Myeloid Leukemia (CML) Polycythemia Vera (PCV) Essential Thrombocythemia (ET) Primary Myelofibrosis (PMF)

Myeloproliferative Disorders

Clonal disorders of hematopoiesis that arise in hematopoietic stem or early progenitor cell.

Characterized by the dysregulated production of particular lineage of mature myeloid cells with fairly normal maturation.

Exhibit a variable tendency to progress to acute leukemia

Share abnormalities of hemostasis and thrombosis Overlap between the clinical features

Introduction

CML is a clonal myeloproliferative neoplasm Dysregulated production and uncontrolled proliferation

of mature and maturing granulocyte with fairly normal differentiation

Fusion of 2 genes: BCR (or chromosome 22) and ABL1 (on chromosome 9), resulting in BCR-ABL1 fusion gene

Final result: Abnormal chromosome 22 called Philadelphia (Ph) chromosome

Final product: BCR-ABL1 fusion protein, a dysregulated tyrosine kinase

Uncontrolled production of mature and maturing granulocytes

Predominantly neutrophils, but also basophils and eosinophils

Triphasic or biphasic clinical course Chronic phase, accelerated phase, blast crisis

Introduction

Phases of CML (before Imatinib)

Chronic phase

Median duration5–6 years

Accelerated phase

Median duration6–9 months

Blast crisis

Median survival3–6 months

Advanced phases

Epidemiology

Annual incidence: 1 to 2 cases per 100,000 15% – 20% of all adult leukemias Incidence increases significantly with age

– Median age: ~ 55 years

– Prevalence increasing due to current therapy

– Most patients present in CP, 85%• Majority of CML-related deaths due to progression to AP/BC

– 50% of CML patients are asymptomatic at diagnosis

Risk factors – Exposure to ionizing radiation, the only known

Molecular Genetics of CML

The Philadelphia chromosome was originally detected by workers in Philadelphia.

The first genetic abnormality to be associated with a human cancer.

The result of a balanced translocation between chromosomes 9 and 22.

Derivative chromosome 22 is significantly smaller Ph chromosome is present in hematopoietic cells from

patients with CML. Therefore, the Ph chromosome is acquired and NOT

inherited through the germline.

Molecular Genetics of CML

The development of chronic phase CML appears to be a direct result of the BCR-ABL1 activity, which promotes its development by allowing:

I. Uncontrolled proliferation of transformed cells

II. Discordant maturation

III. Escape from apoptosis

IV. Altered interaction with the cellular Matrix

The progression of CML from chronic phase to accelerated face or blast crisis is a complex, multistep process (may be related to GMP).

Also, it appears to involve the constitutive expression of the BCR-ABL1 tyrosine kinase.

Molecular Genetics of CML

BCR

ABL

BCRABL

BCR{q11

Ph

9q+

22

9

{q34 ABL

Ph chromosome and bcr-abl gene

bcr-abl

ablFUSION

PROTEINWITH

TYROSINEKINASE

ACTIVITY

22

bcr

Ph (or 22q-)

99 q+

1

p210Bcr-Abl

p190Bcr-Abl2-11

2-11

Chromosome 9

c-bcr

Chromosome 22

c-abl

2-11

Exons

Introns

CML Breakpoints

ALL Breakpoints

t(9;22) translocation bcr-abl gene structure

Philadelphia chromosome t(9;22)(q34;q11)

22q- = Philadelphia chromosome

Clinical Manifestations

Asymptomatic in 20-50% of patients Fatigue 34%, weight loss 20%, excessive sweating

15%, abdominal fullness 15%, bleeding episodes 21% (platelet dysfunction).

Abdominal pain in the LUQ (enlarged spleen) Tenderness over the lower sternum. Acute gouty arthritis Findings: Splenomegaly, anemia, WBC > 100,000,

platelet count > 600,000

Peripheral Blood Pathology

Leukocytosis (median of 100,000) Differentiation shows virtually all cells of neutrophilic

series Blasts < 2% Myelocytes more than metamyelocytes (a classic

finding in CML) Neutrophils cytochemistry is abnormal – low LAP score Basophilia in 90% of cases Thrombocytosis. If low platelets – consider an other

CML Peripheral Blood Smear

CML Peripheral Blood Smear

Bone Marrow Pathology

Granulocytic maturation pattern same as in the peripheral blood

Increased reticulin fibrosis and vascularity Erythroid islands are reduced in number and size Dwarf megakaryocytes Pseudo-Gaucher’s cells and Sea Blue histiocytes

(markers of increased cell turnover) Iron-laden macrophages are reduced or absent

Pseudo-Gaucher cells

Pseudo-Gaucher cells

Sea Blue Histiocyctes

CML – Bone Marrow

Diagnosis of CML

Typical findings in the blood and bone marrow Requires the detection of the Ph chromosomal or its

product, the BCR-ABL1 fusion mRNA and the BCR-ABL1 protein. Conventional cytogenetic analysis (karyotyping) – The first

method Florence and in situ hybridization (FISH) analysis RT-PCR (The BEST) Southern blot techniques – rarely used Western Blotting – low sensitivity and labor intensive

BCR-ABL (FISH)

RT-PCR for BCR-ABL

Qualitative RT-PCR allow for the diagnosis of CML

Quantitative RT-PCR is used to quantify the amount of disease

Allows for the identification of cryptic BCR-ABL translocations

Does not require a bone marrow aspirate for optimal results

Cycle 1 yields 2

molecules

Cycle 2 yields 4

molecules

Cycle 3 yields 8 molecules; 2 molecules

(in white boxes)

match target sequence

Denaturation: Heat briefly to separate DNA strands

Annealing: Cool to allow primersto form hydrogen bond with ends of target sequence

2

1

Extension: DNA polymerase adds nucleotides to the 3” end of each primer

3New nucleo-tides

Primers

Target sequence

Most CML patients are diagnosed in the chronic phase

Chronic phase Blastic phase

Differential Diagnosis

Leukemoid reaction Juvenile myelomonocytic leukemia (JMML) Chronic myelomonocytic leukemia (CMML) Atypical CML Chronic eosinophilic leukemia Chronic neutrophilic leukemia Other myeloproliferative neoplasms Other Ph chromosome positive malignancies

Accelerated Phase CML

10-19% blasts in the peripheral blood or bone marrow

Peripheral blood basophils ≥20% Platelets < 100,000/microL, unrelated to therapy Platelets > 1,000,000/microL, unresponsive to

therapy Progressive splenomegaly and increasing WBC,

unresponsive to therapy Cytogenic evolution

Blastic Phase CML

Blasts in the peripheral blood ≥20% or in the bone marrow ≥30%

Large foci or clusters of blasts on the bone marrow biopsy

Presence of extramedullary blastic infiltrate (e.g., myeloid sarcoma, also known as granulocytic sarcoma or chloroma)

Blast crisis is generally refractory to treatment, occurs approximately 3-5 years after the diagnosis of CML and 18 months after the onset of accelerated face

Blast Phase CML – Bone Marrow

Blast Phase CML – Bone Marrow

Clinical Debate

What is the optimal frontline therapy for CML?

Principles of CML treatment

Relieve symptoms of hyperleukocytosis, splenomegaly and thrombocytosis. Hydration Chemotherapy (Busulfan, hydroxyurea)

Control and prolonging the chronic phase (non-curative) Tyrosine kinase inhibitors Alpha-interferon + chemotherapy Chemotherapy (hydroxyurea)

Treatment Options

Potential cure with allogeneic hematopoietic stem cell transplantation

Disease control without cure using tyrosine kinase inhibitors (TKIs)

Palliative therapy with cytotoxic agents

Treatment decisions for patients with CML are complex, due to the variety of available options, many of which are conflicting.

Factors influencing choice of therapy

Phase of CML Availability of a donor for allogeneic stem cell

transplant Patient age Presence of medical co-morbidities Response to treatment with TKIs

IRIS Study Design: Imatinib Mesylate Versus IFN- + ara-C

S

Imatinib Mesylate

IFN-a + ara-C

R Crossover

IF:· Loss of MCR or CHR· Increasing WBC count· Intolerance of treatment· Failure to achieve MCR at 12 months*· Failure to achieve CHR at 12 months*· Request to discontinue IFN-*

Progression· Increasing WBC count· Loss of MCR or CHR· Accelerated phase or blast crisis· Death

S = screening.R = randomization.

1106 patients enrolled from June 2000 to January 2001

Hematologic Responses

96%

67%

0

10

20

30

40

50

60

70

80

90

100

0 3 6 9 12 15 18 21

% R

esp

ond

ing

Months Since Randomization

Imatinib mesylate

IFN- + ara-C

Cytogenic Responses

Imatinib mesylate

IFN- + ara-C

Months Since Randomization

% R

esp

ond

ing

83%

20%

0

10

20

30

40

50

60

70

80

90

100

0 3 6 9 12 15 18 21

Overall Survival on First-Line Imatinib (IRIS Study)

Resistance to Imatinib occurs predominantly during advanced phase CML

Advanced stage cancers are characterized by multiple genetic changes

Patients in advanced phase often relapse with the development of chemotherapy resistance

Some patients in blast crisis CML respond to Imatinib but then tends to relapse

Chronic Phase

Blast Crisis Relapse

Ph+

Ph+ blastsPh-negative

Ph+ Imatinib mesylate-resistant blasts

Hem

atop

oiet

icdi

ffere

ntia

tion

Bone m

arrow to

peripheral blood

Initial Treatment

Imatinib (Gleevec) Dasatinib (Sprycel) Nilotinib (Tasigna)

Tyrosine kinase inhibitors are for first-line therapy in chronic phase CML

1. All 3 agents are considered to be (category 1) based on the NCCN guidelines and recommendations.

2. Second-generation TKIs (dasatinib or nilotinib) produce faster and deeper response than imatinib

Treatment of CML after failure of initial therapy

No randomized trials have directly compared the efficacy of second-generation TKIs in patients with chronic phase CML who experience failure of an initial TKIs

A trial of another TKI. Dasatinib preferred in patients with pancreatitis, elevated

bilirubin or hyperglycemia Dasatinib crosses the blood brain barrier and would

therefore be preferred in patients with CNS involvement Nilotinib might be chosen for patients with a history of

pleural or pericardial effusion or disease Dasatinib and Nilotinib can result in QT prolongation

Other Options

Bosutinib – toxicity is a limiting factor Ponatinib – toxicity is a limiting factor Increase the dose of Imatinib Omacetaxine mepesuccinate – SQ Injection

Approved by the FDA for patients resistant or intolerant to 2 or more TKIs

Hematopoietic cell transplant – the only cure Clinical trials

Other Options

Interferon alfa plus cytarabineHydroxyureaBusulfan

Patients who are ineligible for HCT but have either a contraindication to a second-generation TKI or have failed to respond to treatment with available TKI

Response Criteria

Hematologic response Cytogenic response Molecular response

Resistance to treatment

Primary resistance – patient fails to achieve a desired response to initial treatment

Secondary resistance – patient with an initial response to a TKI ultimately relapses

Loss of ResponsePatients should be re-evaluated with a bone marrow biopsy with cytogenetics, and BCR-ABL kinase mutation analysis

T315I mutation Resistant to all TKIs, except Ponatinib Patient should be evaluated for SCT

Y253H, E255k/V and F359V/C/I mutations Resistant to Imatinib and Nilotinib but sensitive to Dasatinib

F317L/V/I/C, V299L and T315A mutations Sensitive to Nilotinib but with intermediate sensitivity to

Imatinib and Dasatinib

Mechanisms of action TKIs

They block the initiation of bcr-abl pathway Many TKIs also affect other signaling pathways Dasatinib and Bosutinib inhibit both Bcr-Abl and Src

kinases. Nilotinib inhibits Bcr-Abl, c-kit and platelet derived

growth factor receptor (PDGFR) These differences in targeted pathways may be

responsible for their varied clinical effects in tumors

Mechanisms of Action, Imatinib

Competitively inhibits the inactive configuration of the Bcr-Abl protein tyrosine kinase

Blocking the ATP binding site and thereby preventing a conformational switch to the active form

Inhibits cellular proliferation and tumor formation Produces 95% decrease in CML colony growth Inhibits platelet-derived growth factor and c-kit

GLEEVEC (Imatinib)

GLEEVEC (Imatinib)

Molecular consequence of the t(9;22) is the fusion protein BCR–ABL, which has increased in tyrosine kinase activity

BCR-ABL protein transform hematopoietic cells so that their growth and survival become independent of cytokines

It protects hematopoietic cells from programmed cell death (apoptosis)

TASIGNA (Nilotinib)

Drug Interaction with TKIs

They are metabolized by the CYP3A4 system – can inhibit other cytochrome P450 pathways

Therefore, they compete with Coumadin Low TKIs levels – St. John’s wort, rifampin,

carbamazepine, phenobarbital and phenytoin High TKIs levels – diltiazem, verapamil,

itraconazole, ketoconazole, clarithromycin, erythromycin and grapefruit juice

Side Effects of TKIs

Imatinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects; heart failure; hepatotoxicity

Dasatinib - Bone marrow suppression; pleural/pericardial effusions; pulmonary arterial hypertension; QT prolongation; aspirin like effect

Bosutinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects

Side Effects of TKIs

Nilotinib - Bone marrow suppression; atherosclerosis-related events; electrolyte imbalance; hepatotoxicity Black box: QT prolongation (screening required)

Ponatinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects; heart failure; hypertension; pancreatitis; aspirin-like effect Black box: Arterial thrombosis; hepatic toxicity

Pregnancy and TKIs

All TKIs could be teratogenic during pregnancyWomen are advised not to become pregnant

while on TKIs (any TKI)Best effective contraception is the barrierWoman taking TKIs are advised to avoid to

breast-feeding

Prognosis

Improved dramatically since the incorporation of tyrosine kinase inhibitors into the initial treatment

SEER database. 5138 patient’s, year 2000 and 2005 15-44 years – OS 72 versus 86% 45-64 years – OS 68 versus 76% 65-74 years – OS 38 versus 51% 75-84 years – OS 19 versus 36%

Stage of disease at the time of diagnosis is the strongest single predictor of outcome.

www.tallahasseecancer.com

www.tallahasseecancer.com