laboratory studies cml

8/7/2019 Laboratory Studies cml

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Laboratory Studies

Peripheral blood findings in patients with chronic myelogenous leukemia (CML)

show a typical leukoerythroblastic blood picture, with circulating immature cellsfrom the bone marrow (see image below).

o

Bone marrow film at 400X magnificationdemonstrates clear dominance ofgranulopoiesis. The number ofeosinophils and megakaryocytes isincreased. Courtesy of U. Woermann, MD,Division of Instructional Media, Institutefor Medical Education, University of Bern,Switzerland.

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Bone marrow film at 400X magnificationdemonstrates clear dominance of granulopoiesis.The number of eosinophils and megakaryocytes isincreased. Courtesy of U. Woermann, MD, Division ofInstructional Media, Institute for Medical Education,University of Bern, Switzerland.

The increase in mature granulocytes and normal lymphocyte counts (low

percentage due to dilution in the differential count) results in a total WBC count

of 20,000-60,000 cells/L. A mild increase in basophils and eosinophils is presentand becomes more prominent during the transition to acute leukemia.

o These mature neutrophils, or granulocytes, have decreased apoptosis

(programmed cell death), resulting in accumulation of long-lived cellswith low or absent enzymes, such as alkaline phosphatase (ALP).

Consequently, the leukocyte alkaline phosphatase stains very low to

absent in most cells, resulting in a low score.

o Early myeloid cells such as myeloblasts, myelocytes, metamyelocytes, and

nucleated red blood cells are commonly present in the blood smear,

mimicking the findings in the bone marrow. The presence of the different

midstage progenitor cells differentiates this condition from the acute

myelogenous leukemias, in which a leukemic gap (maturation arrest) orhiatus exists that shows absence of these cells.

o A mild to moderate anemia is very common at diagnosis and is usually

normochromic and normocytic.

o The platelet counts at diagnosis can be low, normal, or even increased in

some patients (>1 million in some).

The bone marrow is characteristically hypercellular, with expansion of the

myeloid cell line (eg, neutrophils, eosinophils, basophils) and its progenitor cells.


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Megakaryocytes (see image below) are prominent and may be increased. Mild

fibrosis is often seen in the reticulin stain.

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The Philadelphia chromosome, which is adiagnostic karyotypic abnormality forchronic myelogenous leukemia, is shown

in this picture of the bandedchromosomes 9 and 22. Shown is theresult of the reciprocal translocation of22q to the lower arm of 9 and 9q (c-abl toa specific breakpoint cluster region [bcr]of chromosome 22 indicated by thearrows). Courtesy of Peter C. Nowell, MD,Department of Pathology and ClinicalLaboratory of the University ofPennsylvania School of Medicine.

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The Philadelphia chromosome, which is a diagnostickaryotypic abnormality for chronic myelogenousleukemia, is shown in this picture of the bandedchromosomes 9 and 22. Shown is the result of the

reciprocal translocation of 22q to the lower arm of 9and 9q (c-abl to a specific breakpoint cluster region[bcr] of chromosome 22 indicated by the arrows).Courtesy of Peter C. Nowell, MD, Department ofPathology and Clinical Laboratory of the Universityof Pennsylvania School of Medicine.

Cytogenetic studies of the bone marrow cells, and even peripheral blood, should

reveal the typical Ph1 chromosome, which is a reciprocal translocation of

chromosomal material between chromosomes 9 and 22. This is the hallmark ofchronic myelogenous leukemia (CML), found in almost all patients with the

disease, and is present in CML throughout its entire clinical course.o The Ph translocation is the translocation of the cellular oncogene c-abl

from the 9 chromosome, which encodes for a tyrosine protein kinase, with

a specific breakpoint cluster region (bcr) of chromosome 22, resulting in a

chimeric bcr/c-ablmessenger RNA that encodes for a mutation proteinwith much greater tyrosine kinase activity compared with the normal

protein (see image above). The latter is presumably responsible for the

cellular transformation in chronic myelogenous leukemia (CML). This m-


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RNA can be detected by polymerase chain reaction (PCR) in a sensitive

test that can detect it in just a few cells. This is useful in monitoring

minimal residual disease (MRD) during therapy.o Karyotypic analysis of bone marrow cells requires the presence of a

dividing cell without loss of viability because the material requires that the

cells go into mitosis to obtain individual chromosomes for identificationafter banding, which is a slow, labor-intensive process.

o The new technique of fluorescence in situ hybridization (FISH) uses

labeled probes that are hybridized to either metaphase chromosomes orinterphase nuclei, and the hybridized probe is detected with

fluorochromes. This technique, a rapid and sensitive means of detecting

recurring numerical and structural abnormalities, is illustrated below.

Fluorescence in situ hybridizationusing unique-sequence, double-fusion DNA probes for bcr (22q11.2)in redand c-abl (9q34) gene regionsin green. The abnormal bcr/ablfusion present in Philadelphiachromosomepositive cells is inyellow (right panel) compared with acontrol (left panel). Courtesy ofEmmanuel C. Besa, MD.

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Fluorescence in situ hybridization usingunique-sequence, double-fusion DNA probesfor bcr (22q11.2) in redand c-abl (9q34) generegions in green. The abnormal bcr/abl fusionpresent in Philadelphia chromosomepositivecells is in yellow (right panel) compared with acontrol (left panel). Courtesy of Emmanuel C.Besa, MD.

o Two forms of the BCR/ABL mutation are present, depending on the

location of their joining regions onbcr

3' domain. Approximately 70% ofpatients who have the 5' DNA breakpoint have a b2a2 RNA message, and30% of patients have a 3' DNA breakpoint and a b3a2 RNA message. The

latter is associated with a shorter chronic phase, shorter survival, and

thrombocytosis.

o Chronic myelogenous leukemia (CML) should be differentiated from Ph-

negative diseases with negative PCR results forBCR/ABL m-RNA. These

diseases include othermyeloproliferative disorders and chronic
http://emedicine.medscape.com/article/204714-overviewhttp://emedicine.medscape.com/article/204714-overview


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myelomonocytic leukemia, which is now classified with the

myelodysplastic syndromes.

o Additional chromosomal abnormalities, such as an additional or double

Ph-positive chromosome or trisomy 8, 9, 19, or 21; isochromosome 17; or

deletion of the Y chromosome, have been described as the patient enters a

transitional form or accelerated phase of the blast crisis as the Phchromosome persists.

o Patients with conditions other than chronic-phase chronic myelogenous

leukemia (CML), such as newly diagnosed acute lymphocytic leukemia(ALL) or nonlymphocytic leukemia, may also be positive for the Ph

chromosome. Some consider this the blastic phase of CML without a

chronic phase. The chromosome is rarely found in patients with othermyeloproliferative disorders, such as polycythemia veraoressential

thrombocythemia, but these are probably misdiagnosed chronic

myelogenous leukemia (CML). It is rarely observed in myelodysplastic

syndrome.

Other laboratory abnormalities include hyperuricemia, which is a reflection ofhigh bone marrow cellular turnover and markedly elevated serum vitamin B-12

binding protein (TC-I). The latter is synthesized by the granulocytes and reflectsthe degree of leukocytosis.

Imaging Studies

Typical hepatomegaly and splenomegaly may be imaged by using a liver/spleen

scan. Most often, these are so obvious that radiologic imaging is not necessary.

Histologic Findings

The diagnosis of chronic myelogenous leukemia (CML) is based on thehistopathologic findings in the peripheral blood and the Ph1chromosome in the bone marrow cells.

Medical Care

The 3-fold goals of treatment of chronic myelogenous leukemia (CML)have changed markedly in the past 10 years. They are: (1) to achievea hematologic remission (normal complete blood cell [CBC] count andphysical examination [ie, no organomegaly]), (2) to achieve

cytogenetic remission (normal chromosome returns with 0% Ph-positive cells), and, most recently, (3) to achieve molecular remission(negative PCR result for the mutational BCR/ABL m-RNA). The last is anattempt for cure and prolongation of patient survival.A new approach to treatment of chronic myelogenous leukemia (CML)is to directly inhibit the molecular cause of the disease, that is, using aprotein-tyrosine kinase inhibitor that inhibits the bcr-abl tyrosine
http://emedicine.medscape.com/article/207347-overviewhttp://emedicine.medscape.com/article/205114-overviewhttp://emedicine.medscape.com/article/205114-overviewhttp://emedicine.medscape.com/article/206697-overviewhttp://emedicine.medscape.com/article/206697-overviewhttp://emedicine.medscape.com/article/207347-overviewhttp://emedicine.medscape.com/article/205114-overviewhttp://emedicine.medscape.com/article/206697-overviewhttp://emedicine.medscape.com/article/206697-overview


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cytogenetic response rate. Overall survival data comparing it with interferon are

shown below.

o A study comparing the efficacy of imatinib with that of interferon alfa

combined with low-dose cytarabine in newly diagnosed, chronic-phase

CML randomly assigned 1106 subjects to receive imatinib (553 subjects)

or interferon alfa plus low-dose cytarabine (553 subjects).16

o After a median follow-up of 19 months, the estimated rate of a major

cytogenetic response (0-35% of cells in metaphase positive for the Ph

chromosome) at 18 months was 87.1% in the imatinib group and 34.7% inthe group given interferon alfa plus cytarabine (P


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and the dose is adjusted depending on the WBC and platelet counts.Most patients achieve hematologic remission within 1-2 months. Thismedication causes only a short duration of myelosuppression; thus,even if the counts go lower than intended, stopping or decreasingdoses usually controls the blood counts. Maintenance with hydroxyurea

rarely results in cytogenetic or molecular remissions.Busulfan (Myleran) is an alkylating agent that has traditionally beenused to keep the WBC counts less than 15,000 cells/L. However, themyelosuppressive effects may occur much later and persist longer,making maintaining the numbers within normal limits more difficult.Long-term use can cause pulmonary fibrosis, hyperpigmentation, andprolonged marrow suppression lasting for months.Leukapheresis using a cell separator can lower WBC counts rapidly andsafely in patients with WBC counts greater than 300,000 cells/L, andit can alleviate acute symptoms of leukostasis, hyperviscosity, andtissue infiltration. Leukapheresis usually reduces the WBC count only

temporarily and is often combined with cytoreductive chemotherapyfor more lasting effects.Interferon alfa was the treatment of choice for most patients withchronic myelogenous leukemia (CML) who are too old for bone marrowtransplantation (BMT) or who do not have a matched bone marrowdonor. Interferon alfa is given at an average of 3-5 million IU/dsubcutaneously after hematologic remission with hydroxyurea.

The cytogenetic response is monitored every 3-6 months by karyotyping or by

fluorescence in situ hybridization to count the percentage of bone marrow cells

with Ph-positive cells.

The goal is 100% normal cells after 1-2 years of therapy. Patients with MRDBCR/ABL positive) should be kept on maintenance therapy as long as they

continue to have MRD.

Cytogenetic improvement has been observed in 70% of patients treated for longer

than 3 months, with the median of Ph'-positive cells declining from 100% to 65%

(range 0-95%). Complete suppression of the Ph' chromosome was observed in

20% of patients.

BMT should be considered early in young patients (


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Most patients with MRD after transplantation require interferon maintenance

therapy anyway, or they may require a reinfusion of T cells collected from the

donor.

Transplantation has been relegated to patients who do not achieve

molecular remissions or show resistance to imatinib and failure tosecond-generation bcr-abl kinase inhibitors such as dasatinib.Mechanisms for resistance to imatinib are: (1) BCR-ABL amplification,and (2) BCR-ABL independent mechanisms such as: (A) Src family ofkinase activation and (B) additional molecular events.Previous exposure to imatinib before transplantation does notadversely effect posttransplant outcomes such as overall survival andprogression-free survival with 90% engraftment, higher relapsedmortality (24%) and lower graft versus host disease (GVHD) (acute,42%; chronic, 17%).20

Treatment decisions involving the use of interferon, BMT, or

investigative options for younger patients with chronic myelogenousleukemia (CML) are extremely complex and in constant flux.Individualized decisions should be made in conjunction withconsultation with physicians familiar with the recent literature.

Surgical Care

Splenectomy and splenic irradiation have been used in patients with large and

painful spleens, usually in the late phase of chronic myelogenous leukemia

(CML).o This is rarely needed in patients whose disease is well controlled.

o Some authors believe that splenectomy accelerates the onset of myeloidmetaplasia in the liver. Splenectomy is associated with high perioperativemorbidity and mortality rates because of bleeding or thrombotic

complications.

Consultations

Patients with chronic myelogenous leukemia (CML) should be underthe care of hematologists and oncologists. Selected patients should beseen by experts in a BMT program in a tertiary care center.

Medication

Cortes et al studied the efficacy of dasatinib as initial therapy for earlychronic phase chronic myeloid leukemia.21Fifty patients wererandomized to receive dasatinib 100 mg qd or 50 mg bid for at least 3months. No difference was noticed between treatment arms regardingoutcome. Of the 50 patients, 49 (98%) achieved a complete
http://emedicine.medscape.com/article/429037-overviewhttp://emedicine.medscape.com/article/429037-overview


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cytogenetic response (CCyR), and 41 (82%) achieved a majormolecular response (MMR).21The projected event-free survival rate at24 months was 88%, and all patients were alive after a median follow-up time of 24 months.The medications used for patients with chronic-phase chronic

myelogenous leukemia (CML) include a myelosuppressive agent toachieve hematologic remission, which requires 1-2 months oftreatment. Once the patient goes into hematologic remission, the goalof treatment is to suppress the Ph-positive hematopoietic clone in thebone marrow for a cytogenetic remission and, hopefully, a molecularremission. This entails the use of interferon alfa or BMT.Treatment is determined by (1) the age of the patient, (2) the presenceof an HLA-matched donor willing to donate bone marrow, and (3) theSokal score. The 3 categories of the Sokal score are (1) low risk, whichis less than 0.8; (2) intermediate risk, which is 0.8-1.2; and (3) highrisk, which is greater than 1.2.

The Sokal score is calculated for patients aged 5-84 years by hazardratio = exp (0.011 (age - 43) + 0 .0345 (spleen - 7.5 cm) + 0.188[(platelets/700)2 - 0.563] + 0.0887 (% blasts in blood - 2.1).The choice of treatment is determined by the prognosis and the age ofthe patient. Most patients have no matched donor or are too old forBMT; interferon alfa is the drug of choice in these patients.

Antineoplastic Agents

To control the underlying hyperproliferation of the myeloid elements, amyelosuppressive agent is necessary to bring down WBC counts and,

occasionally, elevated platelet counts. Spleen size correlates with WBCcounts, and it shrinks as WBC counts approach the reference range.Also, intermediate and myeloblast cells disappear from the circulation.

Hydroxyurea (Hydrea)

Inhibitor of deoxynucleotide synthesis and DOC for inducinghematologic remission in CML. Less leukemogenic than alkylatingagents such as busulfan, melphalan (Alkeran), or chlorambucil.Myelosuppressive effects last a few days to a week and are easier to

control than with alkylating agents; busulfan is associated withprolonged marrow suppression and can cause pulmonary fibrosis.

laboratory studies cml

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