Page 1212 - Hematology_ Basic Principles and Practice ( PDFDrive )

1058 Part VII Hematologic Malignancies

and is associated with deficiency of adenine nucleotides in the storage values of 0.1% or less. Alignment was achieved using laboratory-
pool. The hematocrit is decreased in most patients at diagnosis. Red specific conversion factors calculated by comparisons of results of
cells tend to show only mild alterations with increased variability of assays performed with patient samples against a reference method.
size and shape. Small numbers of nucleated red blood cells and mild A validation procedure was completed, and showed that there was
reticulocytosis may be seen. good agreement between the overall MMR rates between different
Chemical abnormalities seen in patients with untreated CML validated assays. 3
include hyperuricemia and hyperuricosuria. The formation of urate In any new patient whose blood count suggests the diagnosis of
stones is common, and patients with underlying susceptibility may a chronic MPD, the detection of BCR-ABL transcripts in a blood
develop acute gouty arthritis or urate nephropathy. Patients have specimen is probably the best way to confirm the diagnosis of CML.
increased serum levels of vitamin B 12-binding capacity related to Current guidelines recommend that circulating BCR-ABL transcript
release of transcobalamin I and II from mature neutrophils. The numbers be measured and marrow cytogenetics be studied in every
serum B 12 level in CML is an average of 10-fold higher than normal. new patient with CML before initiation of treatment. Marrow
Serum lactate dehydrogenase is elevated in CML. Pseudohyperkale- cytogenetics is essential to identify any unusual translocations or
mia may be seen related to release of potassium from WBCs during additional cytogenetic abnormalities, and RQ-PCR for BCR-ABL at
clotting. Spurious hypoglycemia or hypoxemia may result from diagnosis will identify whether the commonly observed e13a2 (b2a2)
consumption by neutrophils after a sample is drawn. or e14a2 (b3a2) transcripts are present or whether one of the less
Examination of the marrow usually reveals a very hypercellular common fusion transcripts that are not amplified by the standard
marrow, with 75% to 90% marrow cellularity (see Fig. 67.2C and primer sets is present. This can prevent confusion if a patient on
D). The granulocytic-to-erythroid ratio is increased to 10 : 1 to 30 : 1, therapy has undetectable BCR-ABL transcripts because their tran-
with increased granulopoiesis and reduced erythropoiesis. Eosinophils scripts were not amplified in the standard assay. If collection of
and basophils may be increased. Blasts usually represent fewer than marrow cells is not feasible, FISH performed on a blood specimen
5% of cells. The presence of more than 10% blasts indicates trans- using dual probes for the BCR and ABL genes is an alternate method
formation to AP. Megakaryocytes are typically smaller than usual and of confirming the diagnosis. FISH may also detect cytogenetically
may have hypolobated nuclei. Megakaryocyte numbers may be “silent” BCR-ABL rearrangements and deletions in the derivative 9q+,
normal or slightly decreased, but 40% to 50% of patients show which have prognostic significance, and may therefore be performed
moderate-to-extensive proliferation of megakaryocytes. Collagen type in conjunction with marrow cytogenetics and RQ-PCR for BCR-ABL
III detected by silver staining is typically increased (see Fig. 67.2E). transcripts.
Approximately half of patients demonstrate increased reticulin
fibrosis, which may be associated with increased megakaryocytes in
marrow. Increased fibrosis may be associated with larger spleen size, Natural History
anemia, and increased blasts in blood and marrow. Pseudo-Gaucher
cells and sea-blue histiocytes, secondary to increased marrow cell The natural history of CML, determined more than 75 years ago,
turnover, may be seen in 30% of specimens (see H5eC69, Fig. suggests a median survival from diagnosis of approximately 3 years.
67.2F). The spleen shows enlargement related to infiltration of the Without therapy, CML evolves from a CP to an AP, and eventually
cords of the red pulp with granulocytes at different stages of matura- to BC. In approximately 25% of patients, there is no intervening AP
tion. The liver may show infiltration with granulocytic cells in the between CP and BC (Table 67.1). Median survival times have been
portal areas and hepatic sinusoids. significantly prolonged with therapy (discussed later in the Therapy
Cytogenetic examination shows t(9;22)(q34;q11) and Ph chro- section). Following the introduction of imatinib treatment, a dra-
mosome in more than 90% of patients. Additional chromosomal matic decrease in CML deaths was seen in age-adjusted death data
abnormalities besides the Philadelphia chromosome are seen at from the US Surveillance Epidemiology and End Results (http://
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diagnosis in 20% of patients including –Y and +8, and have not seer.cancer.gov/statistics/). Long-term follow-up of CML patients
been shown to affect disease course. Variant Ph chromosomes are seen who achieved complete cytogenetic response (CCR) 2 years after
in 5% of patients, with complex rearrangement involving exchange starting imatinib treatment showed that CML-related deaths are
of material with an additional chromosome besides chromosomes uncommon and survival is not statistically significantly different from
9 and 22. In a small proportion of patients cryptic or complex that of the general population. 5
translocations can be detected by fluorescence in situ hybridization
(FISH) or PCR assays. The methodology used for identifying BCR-
ABL transcripts has evolved over the years. Initially it was possible Accelerated Phase
only to identify the presence or absence of BCR-ABL transcripts by
either single-step amplification or a two-step “nested” amplification In general, AP is characterized by symptoms of fever, night sweats,
with internal primers to increase the sensitivity. Real-time quanti- weight loss, and bone pain, difficulty in controlling counts using
tative PCR (RQ-PCR) provides an accurate measure of the total conventional therapy, increased numbers of blasts and early myeloid
leukemia cell mass, and the degree to which BCR-ABL transcripts cells in marrow and peripheral blood, and evidence of karyotypic
are reduced by therapy correlates with progression-free survival evolution (Fig. 67.3). The World Health Organization classification
(PFS). A consensus meeting at the National Institutes of Health in defines AP of CML as one or more of the following changes: (A)
October 2005 made suggestions for (A) harmonizing the different 10% to 19% myeloblasts in peripheral blood or bone marrow; (B)
methodologies for measuring BCR-ABL transcripts in patients with peripheral blood basophils higher than 20%; (C) persistent throm-
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CML undergoing treatment and using a conversion factor whereby bocytopenia, less than 100 × 10 /L; (D) persistent thrombocytosis,
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individual laboratories can express BCR-ABL transcript levels on an more than 1000 × 10 /L unrelated to therapy; (E) increasing WBC
internationally agreed scale; (B) using serial quantitative-PCR results count and increasing spleen size unresponsive to therapy; and/or (F)
rather than bone marrow cytogenetics or FISH for the BCR-ABL evidence of clonal evolution. The most common cytogenetic changes
gene to monitor individual patients responding to treatment; and associated with disease evolution are an additional Ph chromosome,
(C) detecting and reporting Ph-positive subpopulations bearing BCR- trisomy 8, isochrome I(17q), and trisomy 19.
ABL kinase domain mutations. An international scale for comparison
of BCR-ABL mRNA levels has been subsequently developed and
implemented to facilitate common interpretation of data derived Blast Crisis
from individual laboratories and comparison of clinical studies, as
well as to guide clinical decision. BCR-ABL values generated by The blast phase of CML resembles acute leukemia. BC is defined as
different laboratories were aligned to the international scale such having more than 20% blasts in the bone marrow or peripheral
that major molecular response (MMR) was defined as BCR-ABL blood, the presence of large aggregates and clusters of blasts in the