MPNs Flashcards
CML Chronic Phase
<10% blasts (usually less than 2%)
Often anemia and thrombocytosis
Paratrabecular cuff immature grans 5-10
Megas tend to cluster, unlike AML t(3;3), inv(3)
40% have mildly increased reticulin fibrosis
CML Accelerated Phase
One or more of the following:
Persistent or increasing WBC (>10 x 109/L) or splenomegaly
Persistant thrombocytosis (>1000 x 109/L)
Persistant thrombocytopenia (<100 x 109/L)
Cytogenetic evidence of clonal evolution
PB basophils ≥ 20%
10-19% blasts in PB or BM
CML Blast Phase
One or more of the following:
PB or BM blasts ≥ 20% (70% AML, 25% B-ALL, rare T-ALL)
Extramedullary blast proliferation (i.e. myeloid sarcoma)
Large foci or clusters of blasts in the BM bx (entire intertrabecular region)
*Still continue to treat with TKIs, not chemo*
CML vs Leukemoid Rxn
CML:
decreased alkaline phosphatase (decreased LAP score)
myelocyte bulge
Leukemoid Rxn:
increased alkaline phosphatase (increased LAP score)
no myelocyte bulge
BCR-ABL1
- 90-95% have the Ph (del22) chromosome
- Most of the remaining cases have variant genetic abnormalities that resutl in the BCR-ABL1 fusion gene but involve other chromosomes in addition to 9 and 22
- Very few have cryptic BCR-ABL1 translocations that cannot be identified by routine karyotyping and requite molecular or FISH
- Remember BCR is on chr.22 and ABL1 is on chr.9
Sensitivities of Techniques for BCR-ABL1
karyotype= 90-95%
RT-PCR= 99%
FISH= >99%
p210
BCR exons 12-16
Transcripts:
b2a2
b3a2 (most common translocation)
p230
BCR exons 17-20
Transcript: e19a2
Marked thrombocytosis or neutrophilia (resembling CNL)
p190
BCR exons 1-2
Transcript: e1a2 (less commonly e1a3)
B-ALL
CML with increased monocytes (resembling CMML)
***A small amount of the p190 transcript can be detectedin >90% of pts with p210 CML due to alternative splicing of the BCR gene***
Cytogenetic changes seen in transformation
extra Ph
+8
+19
i(17q)
Which pts should have kinase domain mutation testing?
1) all high risk pts
2) standard risk pts who fail to achieve complete cytogenetic response by 6mos
3) pts showing loss of response to imatinib, relapse to Ph+, or increased BCR-ABL1 transcript by ≥1 log
4) at time of progression to accelerated or blast phase
Complete Hematologic Response
PB counts completely return to normal, including plt count
No blasts or immature cells circulating
No signs/sx of disease including no enlarged spleen
Complete Cytogenetic Response
No Ph chromosome detected with BM cytogenetics
Partial Cytogenetic Response
1-35% of cells have the Ph chromosome on BM cytogenetics
Major Cytogenetic Response
0-15% of cells have the Ph chromosome on BM cytogenetics
(complete + partial response)
Complete Molecular Response
No BCR-ABL1 copies detectable by QPCR using the IS
Major Molecular Response
≥3 log reduction in BCR-ABL1 levels
OR
BCR-ABL1 0.1% by QPCR using IS
Relapse
- Any sign of loss of response: defined as hematologic or cytogenetic relapse
- A 1-log increase in BCR-ABL1 levels with loss of major molecular response should prompt BM evaluation (but is not alone defined as relapse)
Most important prognostic indicator
Response to TKI at the hematologic, cytogenetic, and molecular level
Minor Cytogenetic Response
>35% of cells have the Ph chromosome on BM cytogenetics
Cytogenetic Response Rate to Imatinib
70-90%, with 5 year progression free survival/overall survival 80-95%
BCR gene
25 exons, including two putative alternative first (e1’) and second (e2’) exons
ABL1 breakpoints
Almost invariably occur:
1) upstream of exon Ib
2) b/w exon Ib and Ia
3) b/w Ia and a2
Mechanisms of Drug Resistance
- kinase domain mutations
- BCR-ABL1 gene amplification or protein overexpression
- alterations in drug efflux kinetics
- upregulation of other kinase pathways
- rare BCR-ABL1 mutations outside of the kinase domain
Drugs for pts with Imatinib resistance
dasatinib
nilotinib
bosutinib
Relapsed Ph+ ALL
80-90% will have a BCR-ABL kinase domain mutation
Kinase Domain Mutation Testing
- Direct sequencing of BCR-ABL1 gene by Sanger method (because detection of low level mutant clones may not be clinically significant)- detects a mutation in 1 in 5 BCR/ABL1 transcripts
- low level imatinib resistance in M351T, with probable response to dose escalation
- high level resistance T315I, Y253H, E255K, with need for change in therapy
- T315I mutation is relatively common and the worst (resistant to almost all TKIs)
Diagnostic Criteria for CNL
- WBC ≥25 x 109/L (>80% PMNs & bands, <10% pros/myelos/metas, <1% blasts)
- hypercellular BM
- hepatosplenomegaly (most have splenomegaly)
- no BCR-ABL1 fusion gene
- no rearrangement of PDGFRA, PDGFRB, FGFR1
- no evidence of PV, ET, or PMF
- no evidence of MDS or MDS/MPN (no dysplasia, monos<1 x 109/L)
- no physiologic cause for neutrophilia or if so, demonstration of myeloid clonality
Morphology of CNL
- Marked increase in PMNs and bands, almost never myeloblasts
- PMNs appear toxic
- Up to 20% of cases are associated with another neoplasm, usually myeloma (where CNL is thought to be 2º to abnormal cytokine release from neoplastic plasma cells)
- If plasma cell dyscrasia is present, clonality of PMN lineage shoudl be proven by cytogenetics or molecular studies before diagnosing CNL
Mutation Associated with CNL
- many cases show a mutation of the CSF3R gene
- cytogenetics normal in 90% cases
- JAK2 mutations have also been described
- ?SETBP1?
3 Phases of Polycythemia Vera
1) Prodromal (prepolycythemic) phase: symptoms suggestive of PV, borderline-mild erythrocytosis
2) Overt polycythemic phase: significant ↑ RBC mass
3) “Spent”/post-polycythemic phase: cytopenias (including anemia), PB leukoerythroblastosis, BM fibrosis, splenomegaly, and extramedullary hematopoiesis
Signs and Symptoms of PV
HTN
vascular abnormalities (venous/arterial thrombosis, MI/stroke, Budd-Chiari)
plethora/pruritis
HA/dizziness
visual changes
gout (hyperuricemia from high cell turnover)
hepatosplenomegaly (usually mild)
PV Diagnostic Criteria
Requires both major + 1 minor OR first major + 2 minor
Major:
- Hgb >18.5 g/dL in men, >16.5 g/dL in women (or other evidence of ↑ red cell volume)
- JAK2 V617F or JAK2 exon 12 mutation
Minor:
1. Hypercellular marrow showing panmyelosis
- Low serum EPO
- Endogenous erythroid colony formation in vivo
Pre-polycythemic and Polycythemic Stages
PB shows increase in all 3 lineages (thrombocytosis in about 50%)
BM shows:
- left shifted granulocytes
- pleomorphic megas (less than PMF, more than ET) dispersed or loosely clustered
- enlarged erythroid islands that tend to form sheets
- absent stainable iron***
“Spent”/Post-polycythemic Phase
PB shows leukoerythroblastosis, poikilocytosis with frequent dacrocytes
BM shows reticulin & collagen fibrosis
↑ splenomegaly 2º/2 EMH
***Lymphoid aggregates are seen in 20%***
JAK2
- cytoplasmic tyrosine kinase acts through JAK-STAT family of nuclear receptors
- V617F is most common mutation, due to G→T point mutation in exon 12 (valine to phenylalanine)
- mutation happens in pseudokinase domain (usually turns of TK activity), leads to constitutive activation of JAK2
- mutually exclusive with CALR mutations
Cytogenetic Abnormalities PV
10-20% of patients
+8
+9
del(20q)
del(13p)
del(1p)
PV Treatment & Prognosis
Phlebotomy
Pegylated interferon effective in reducing risk of thrombosis and progression to fibrosis
Most pts die from thrombosis/hemorrhage (median survival 10yrs)
Up to 20% pts develop MDS or AML
Primary Myelofibrosis Clinical
90% of patients have splenomegaly
BCR/ABL1 Drug Resistance Mutations- General
- among pts with chronic phase CML, who develop secondary resistance to imatinib, 30-50% will have one or more BCR/ABL1 kinase domain mutations detectable by DNA sequencing
- mutation frequency higher in those with accelerated/blast phase (especially lymphoid blast phase)
- 80-90% pts w/relapsed Ph+ ALL will have BCR/ABL1 KD mutation
- absence of mutation does not exclude resistance by other mechanisms
BCR/ABL1 Drug Resistance Mutations- Indications for Testing
- chronic phase for those with inadequate initial response to TKIs or those with evidece of loss of response (10-fold or greater increase in transcript levels)
- at time of progression to accelerated or blast phase
