CML Flashcards
epidemiology of CML
> male
40-60yrs at presentation
radiation exposure is a RF
Hx of CML
Lethargy/ hypermetabolism/ thrombotic event : monocular blindness CVA (plts may be increased), bruising bleeding
Massive splenomegaly +/- hepatomegaly
The spleen enlarged due to infiltration of cords and red pulp by granulocytes (which may even obliterate the white pulp)-the same process occurs in the liver hepatic sinusoids
In case of massive splenomegaly, splenic infarction may occur
if have massive liver adn spleen what disease thinking
myeloid so - CML or primary myelofibrosis
if massive liver, spleen and nodes what disease thinking
slow growing indolent lymphoid:
follicular lymphoma or CLL
blood in CML
Hb and platelets well preserved or raised (contrast acute leukaemia)
Massive leucocytosis 50-200x109/L
Blood film
* Neutrophils and myelocytes (precursers from marrow spilling into blood)
* Basophilia
* Leucocytosis between 50 – 500x109/l
* Mature myeloid cells
* No excess (<5%) myeloblasts
why do platelets fall in acute leukaemia
marrow is filled with primitive lineages
so all lineages fall
get immature cells leaking out
DNA of CML
philidelphia chr - t(9,22) - bcr-Abl
reciprocal translocation between chr 9 and 22 - move ABL oncogene to break point cluster region (Bcr) -> synthesis of abnormal protein (210kDa) with TK activity greater than normal ABL
ABL – tyrosine residue – important for signal translocation
New gene with constant activation of abl
site of bcr can influence the phenotype of the disease
In CML the breakpoint on the BCR gene is nearly always in the major breakpoint cluster region (M-BCR)
diagnostic technique to identify t(9,22)
- Conventional Karyotyping
- FISH metaphase or interphase karyotyping
- RT-PCR amplification and detection
Can do in metaphase: prepare karyotype and stain with probe – diff colour for 9 and 22
Then find philidlphia and changed chr 9 where translocation has occurred – this is the diagnosis of CML
normal has 2 green and 2 red signals
yellow = fusion gene
PCR for dx of CML
Reverse transcription is converting mRNA -> cDNA then probe for mRNA
In normal cell – find Bcr cDNA and Abl cDNA using 3’ and 5’ for both abl and bcr
If instead, you use 3’able and 5’bcr – will not be able to amplify the bcr gene or abl gene
In CML – will get product – cDNA that crosses translocation – so have bcr at one end and abl at other – it must be cml.
natural hx of CML
3-4 hx of CML chronic phase:
* well
* making more granulocytes, if V high could have stroke, blindness, priapism
* Could give hydroxycarbamide and would live fine
Endless proliferation of granulocyte precurser gives rise to mutations -> more problematic subclones -> accelerated phase (6-12mo)
-> acquire mutation in differentiation programming genes -> AML (Occasionally can go from CML -> ALL)
* surival 3-6mo
* cells don’t mature,
* retain proliferation,
* marrow overwhelmed, thrombocytopenia ->
* die from neutropenia and gram –ve sepsis
what is imatinib
an Abl tyrosine kinase inhibitor
CML No longer transforming into blast transformation
not everyone will survive on it
all CML get started on imatinib - if get molecular response in 12-18mo outlook is good - likely to survive
assess response to imatinib
Haematological response
Complete Haematological Response WBC<10x109/l
Cytogenetic response (on 20 metaphases)
Partial 1-35% Philadelphia positive
Complete 0% Ph positive – got rid of the response at this level of detection
Molecular ( reduction in % BCR-ABL transcripts ie looking for fusion gene on PCR )
Much more sensitive - so can determine what proportion of cells have gone
BCR-ABL transcripts reduce 100% > 10% > 1% > 0.1%
Major Molecular response (MMR) <0.1% (3 log reduction)
treatment of CML
start oral TKI (Imatinib (1Gen,) Dasatanib Nilotinib (2G) Bosutinib (3G))
Monitor response FBC, Cytogenetics, RQ-PCR
if good response at 1 yr -> good 5yr survival
if fail - switch to 2nd or 3rd generation TKI
if fail again - allogenic SCT - if inadequate response/intolerant of 2nd generation TKIs or progression to accelarated/blast crisis
why are tyrosine kinases not a panacea
Failure to achieve CCyR
Non compliance
Side effects; fluid retention pleural effusions
Loss of MMR
* Acquiring abl point mutations -> resistance
* Evolution to blast crisis
