18.06.16 ALL Flashcards
(39 cards)
What is ALL?
ALL is a neoplasm characterised by clonal expansion of leukemic cells in the BM, lymph nodes, thymus or spleen.
ALL accounts for 75% of childhood leukaemia (85% B-cell, 15% T-cell) and 6% of adult leukaemia (75% B-cell, 25% T-cell).
What are the features of Adult ALL?
ncidence 0.9-1.6/100,000 (> 60yo) and 0.4-0.6/100,000 (25-50yo). Males are more often affected than females.
Clinical features variable and depend on extent of disease; fever, fatigue, bone/joint pain, headache, weight loss, Shortness of breath, Swollen lymph nodes, particularly lymph nodes in the neck, armpit, or groin, which are usually painless, Swelling or discomfort in the abdomen, bruising, infections, lymphadenopathy, hepato/splenomegaly, and commonly haematological abnormalities including anaemia, leucocytosis, neutropenia, thrombocytopenia.
Why is genetic testing useful at diagnosis in Adult ALL?
Genetic testing at diagnosis allows prognostic classification, which can help determine intensity of treatment regimen (along with other factors including age WCC at presentation, sex, immunophenotype, MRD response), in order to avoid over or under treating (risk adapted therapy). NB cytogenetics stratification is less important in T-ALL, no current protocols use this info.
Cytogenetic testing can also dictate the use of a particular drug e.g. TKI added to therapy in cases with t(9;22) and can aid diagnosis e.g. distinguish between B-ALL and Burkitt lymphoma where therapies differ.
What are the most significant genetic prognostic factors for adult B-cell ALL?
t(9;22)(q34;q11) BCR-ABL1 Philadelphia chromosome.
t(4;11)(q21;q23) KMT2A (MLL)-AFF1
Complex karyotype
Hyper hyperdiploidy (51-65 chr)
Hypodiplody (<44 chromosomes) and near triploidy
TCF3 rearrangements
IGH@ rearrangements
Describe t(9;22)(q34;q11) BCR-ABL1 Philadelphia chromosome in B-cell ALL
Poor prognosis (9% 5 year survival)
25-30% of adult ALL (most common rearrangement in adult ALL)
Use of TKI therapy has been shown to enhance the long-term outcomes in Ph+ve ALL (Fielding et al Blood 2014, 123:843-850) and allo BMT may not be mandatory.
Recent paper from the Leuk Res Cyto Group (Chilton et al Leukaemia 2014, 28:1511-1518) indicates that the co-existence of HeH ameliorates the adverse effect of Ph positivity (1232 patients 15-65 yo).
Common secondary abnormalities include: +Ph, -7/7q-,del(9p), +8, +X, and HeH.
~25% of Ph +ve ALLs p210 BCR-ABL1 fusion; 75% p190 (minor BCR breakpoint). p190 is only found in de novo ALL, while p210 s seen in de novo ALL and CML in lymphoid blast crisis (can determine by RT-PCR).
Recent studies have shown that the majority of Ph+ve ALLs and lymphoid BC CMLs show a deletion if IKZF1 (7p21) [significance unclear].
Describe t(4;11)(q21;q23) KMT2A (MLL)-AFF1 in B-cell AML.
Poor prognosis (33% 3 year survival)
KMT2A rearrangements are seen in ~10% adult ALL [most common t(4;11)].
KMT2A rearrangements may occur in B or T-ALL.
The KMT2A gene encodes a 430 kd nuclear protein thought to be a positive regulator of gene expression in early embryonic development and haematopoiesis. HOX genes are a prominent downstream target dysregulated by the fusion protein.
> 80 partners identified so far.
Prognosis of other KMT2A rearrangements is not certain therefore important to distinguish t(4;11) (commericially available dual-fusion FISH probes).
Other KMT2A rearrangements frequently seen in ALL are t(9;11) (KMT2A-MLLAT3) and t(11;19) (KMT2A-ENL), t(10;11) (KMT2A-MLLT10).
What is the significance of a complex karyotype in adult B-cell ALL?
Poor prognosis (28% 5 year survival)
What is the significance of high hyperdiploidy in adult B-cell ALL?
Good prognosis.
~7% adult ALL
Commonly gained: 4, 6, 10, 14, 17,18 , 21 (often 2 copies gained) and X.
Structural abnormalities: dup(1q), del(6q), abn 9p, abn 12p.
HeH not a mutually exclusive event. If a structural rearrangement such as t(9;22), t(4;11) or t(1;19) is also present the hyperdiploidy is thought to be a secondary event- reported to ameliorate the effects of t(9;22), see above.
What is the difference between doubled up near haploid/low hypodipoloidy karyotype and a true hyperdiploid?
Important to distinguish between a doubled up near haploid/low hypodiploidy karyotype and a true hyperdiploid.
True hyperdiploid: gained chromosome tend to be trisomic (other than 21 and X)
Doubled up near haploid/low hypodiploid: usually 4 copies of gained chromosomes.
If the presence of two clones cannot be demonstrated by FISH/G-banding then flow cytometry to measure DNA index or STR zygosity testing (most duplicated chromosomes will be homozygous).
What is the significance of Hypodiplody (<44 chromosomes) and near triploidy in adult B-cell ALL?
Poor prognosis
Incidence = 4% 15-29 years, 16% >60 years. 22% 5 year overall survival). In Moorman et al’s study (2007) these two entities were classified as one subgroup as these karyotypes have been shown to represent a single distinct subtype of adult ALL.
Commonly retained: 1, 4, 5, 6, 8, 10, 11, 18, 19, 21, 22 and sex chromosomes (common losses of 3 and 7).
Low hypodiploidy more common than near haploidy (converse is true for infants).
What is the significance of TCF3 rearrangements in adult B-cell ALL?
Adult incidence is <5% of B-ALL. The t(1;19), which can occur in a balanced or unbalanced form [der(19)t(1;19)] is the most common rearrangement resulting in TCF3-PBX1 gene fusion. The fusion protein has an oncogenic role as a transcriptional activator. Important to characterise a TCF3 break-apart FISH result or equivocal cyto result as the t(1;19) has in intermediate prognosis and the rare t(17;19) (TCF3-HLF fusion) has a poor prognosis.
What proportion of adult T-cell ALL have a detected cytogenetic abnormality?
50-70%
What are the common rearrangements detected in adult t-ALL?
Approximately 35% of cases show rearrangements involving the TCR loci at 7q34 (TCRB) or 14q11 (TCRA/D).
The lack of trial data means that the prognostic significance of most T-ALL rearrangements remains uncertain; however, a complex karyotype (5 or more abnormalities) is associated with a poor prognosis in adult ALL. Numerical abnormalities are less common than in B-ALL.
TLX1-TRA/TRD t(10;14) recognised finding; prognostic significance under debate. According to data from UKALL XII/ECOG 2993 trial (Marks et al Blood 2009 114:5136-45) TLX1 rearrangements are not associated with a good prognosis as previously reported.
No FISH testing is mandatory as at present patients with T-ALL are not stratified on the basis of genetic findings.
NOTCH1 receptor activating mutations are also common in T-ALL (60%). More rarely NOTCH1 is activated by the t(7;9) translocation where is juxtaposed with TRB. Patients with mutation in NOTCH pathway may have a higher event free survival than those without.
Some AL patients cannot be assigned to a particular cell lineage. What is a common abnormality detected in these patients?
t(9;22)
KMT2A rearrangements
trisomy 13
What are the disadvantages of karyotyping of bone marrow samples?
normal marrow outgrowing leukemic clone apoptosis of leukemic cells high failure rate poor quality metaphases cryptic/subtle rearrangements. Growth factor supplements e.g. SCF, interleukins, FLT3 ligand can be added during incubation of B-ALL to improve QA. (or PHA for T-cell cultures.
How can multiplex RT-PCR be applied to ALL and AML patients?
Multiplex RT (reverse transcription)-PCR can be used as a molecular technique to identify the most common fusion transcripts in ALL or AML. This method also allows identification of the exact breakpoint so that molecular monitoring of disease can be undertaken during treatment
Other techniques are now playing an increasingly important role e.g. MLPA or arrays to detect prognostically relevant deletions such as IKAROS (IKZF1) and sequencing can be used to detect point mutations. Future trials are likely to incorporate some exome and MLPA screening. This will allow improved risk stratification.
Microarrays and NGS have discovered new genes associated with ALL?. Give examples.
IKZF1 (7p21)
Other genes frequently deleted in B-ALL include PAX5, EBF1 and BTG1.
Recently mutations or deletions of CREBBP (histone acetyltransferase) have been shown to be present in 20% of cases of relapsed ALL. It is thought that these mutations may influence response of leukemic cells to chemotherapy and therefore the use of histone deacetylase inhibitors may be an important therapeutic approach in the treatment of high risk and relapsed ALL.
What is the significance of IKZF1 in ALL?
a master regulator of lymphocyte development and differentiation. Alterations (deletions/mutations) are seen in ~15% of B-ALL and are associated with a poor outcome. Deletions/mutations of IKZF1 are found in 80% of Ph+ve ALL. Deletions can be detected by MLPA (or SNP array) and may be incorporated into childhood risk stratification within the next few years. Other genes frequently deleted in B-ALL include PAX5, EBF1 and BTG1.
Why might interphase FISH be useful in ALL patients?
Chromosome analysis in remission is not mandatory.
Due to the difficulty of detecting a potentially low number of poor quality ALL metaphases, interphase FISH may be helpful.
MRD is best monitored by molecular means (e.g. q-PCR or PCR analysis of Immunoglobulin and TCR gene rearrangements) or flow cytometry.
At relapse cytogenetic analysis may identify karyotype evolution or secondary malignancy.
What are the symptoms of ALL?
symptoms of ALL include bruising or bleeding due to thrombocytopenia, pallor and fatigue from anemia, and infection caused by neutropenia. Leukemic infiltration of the liver, spleen, lymph nodes, and mediastinum is common at diagnosis
Describe paediatric ALL
It is the most common malignancy in children (25% of pediatric cancer). Incidence in childhood 3~4/100,000 per year (in adults it is <1). The peak age in children is at 2-5 years.
ALL accounts of 75% of childhood leukaemia (85% B-cell, 15% T-cell)
What is infant ALL?
Infant ALL (<1year) is rare. The biological features are different from ALL in older children, with infant ALL having an immature B phenotype lacking CD10 expression, with a higher tumour load at presentation. Overall survival is considerably worse for infant ALL than for older children. 15-20% of children with ALL will relapse.
What are the most signifiant prognostic rearrangements in paediatric infant/childhood B-ALL
t(9;22)(q34;q11) BCR-ABL1 rearrangement;
KMT2A (MLL) rearrangements
t(12;21) ETV6-RUNX1 rearrangement
iAMP21 (intrachromosomal amplification of chrm 21)
High Hyperdiploidy (51-65 chromosomes).
Describe t(9;22)(q34;q11) BCR-ABL1 rearrangement; in paed B-ALL
Seen in 2-4% of childhood ALL, associated with poor prognosis.
The BCR-ABL1 fusion protein shows constitutive ABL1 kinase activity, conferring a growth and survival advantage.
~25% of Ph +ve ALLs p210 BCR-ABL1 fusion; 75% p190 (minor BCR breakpoint). p190 is only found in de novo ALL, while p210 s seen in de novo ALL and CML in lymphoid blast crisis (can determine by RT-PCR).
The prognosis of Ph+ve ALL was dire until the advent of TKIs. Initially imatinib was combined with intensive chemotherapy. 3 year EFS rates as high as 80% in children and 60% in adults The introduction of 2nd generation TKIs has raised the possibility that less intensive chemo may be used and allo BMT may not be mandatory.
Recent paper from the Leuk Res Cyto Group (Chilton et al Leukaemia 2014, 28:1511-1518) indicates that the co-existence of HeH ameliorates the adverse effect of Ph positivity independent of age; however, study only included patients 15-65 yo therefore effect on children <15 not clear. Currently, in these patients poor prognosis of the 9;22 overrules the favourable prognosis of the hyperdiploidy.
Recent studies have shown that the majority of Ph+ve ALLs and lymphoid BC CMLs show a deletion if IKZF1 (7p21) [significance unclear].
