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Myelofibrosis (MF) is a complex hematologic disorder characterized by dysregulation of the bone marrow stroma developing a reticulin fibrosis. High-throughput sequencing has demonstrated the various functions of somatic nondriver mutations, or additional mutations, such as splicing, signalization, and transcription factors, and therefore ‘high-risk’ genes are now included in the new scoring systems in primary myelofibrosis (PMF).
Although the prognostic function of additional mutations has been confirmed in PMF, there is limited data on secondary myelofibrosis (SMF). A genomic analysis study by Paz et al. investigating the prognostic impact of the mutational landscape in PMF and SMF, was published in Blood Advances and co-authored by two MPN Hub Steering Committee members, Stéphane Giraudier and Jean-Jacques Kiladjian.1 The key findings are summarized below.
The MPN Hub has previously reported on the gene expression profile in MF subtypes.
This was a genomic analysis study analyzing DNAs from unselected patients (N = 479) with PMF or SMF, registered in the French Intergroup of Myeloproliferative Neoplasms (FIM) observatory of MF. Samples of whole blood, purified blood granulocytes, or whole bone marrow were collected. Clinical and biological data were extracted at diagnosis and follow-up.
Median time between diagnosis and sampling was 17 days (range, 0–88 months). Patient characteristics are summarized in Table 1. Of all the patients with SMF, 70 had post-polycythemia vera (post-PV) MF, and 104 had post-essential thrombocythemia (post-ET) MF.
Table 1. Baseline characteristics*
M, male; MF, myelofibrosis; F, female; PMF, primary myelofibrosis; SMF, secondary myelofibrosis. |
|||
Characteristic |
MF (N = 479) |
PMF (n = 305) |
SMF (n = 174) |
---|---|---|---|
Sex (M/F), % |
64/36 |
71/29 |
52/48 |
Age at diagnosis, mean, years (range) |
66 (18−89) |
68 (18−88) |
67 (31−89) |
Hemoglobin (g/dL), mean (range) |
11.1 (6.2−18) |
11.1 (6.3−17.2) |
11.1 (6.2−18) |
Platelets at diagnosis (109/L), mean (range) |
272 (16−999) |
250 (16−999) |
323 (19−980) |
Leukocytes at diagnosis (109/L), mean (range) |
9.7 (1.3−76) |
9.5 (1.7−76) |
9.8 (1.3−68) |
Driver mutations, % |
|||
JAK2 V617F |
65 |
61 |
70 |
CALR |
23 |
24 |
21 |
MPL |
5 |
6 |
3 |
Double mutation |
2 |
1 |
2 |
Triple negative |
6 |
7 |
3 |
Four prognostic groups based on their impact on overall survival (OS) were developed (Table 2).
Table 2. Prognostic groups*
*Adapted from Paz et al.1 |
||
Additional mutations |
Patients, n |
Risk group |
---|---|---|
TP53-mutated |
27 |
TP53 |
≥1 mutation in EZH2, CBL, U2AF1, SRSF2, IDH1, IDH2, NRAS, or KRAS |
150 |
High-risk |
ASXL1-only mutation (no associated mutation in TP53 or in high-risk genes) |
74 |
ASXL1-only mutation |
Mutations in NFE2, DNMT3A, TET2, and SF3B1 |
228 |
‘Other’ patients |
Table 3. Multistate model for AML and death*
AML, acute myeloid leukemia; HR, hazard ratio; MF, myelofibrosis; PMF, primary myelofibrosis. |
||||||
Characteristic |
MF to AML |
MF to death |
AML to death |
|||
---|---|---|---|---|---|---|
HR (95% CI) |
p value |
HR (95% CI) |
p value |
HR (95% CI) |
p value |
|
Age, years |
— |
— |
1.05 |
<0.0001 |
— |
— |
Sex, male |
— |
— |
1.41 |
0.077 |
— |
— |
Hemoglobin |
— |
— |
0.81 |
<0.0001 |
— |
— |
Leukocytes |
— |
— |
1.04 |
<0.0001 |
— |
— |
Platelets |
0.99 |
0.012 |
— |
— |
— |
— |
Driver mutation†: CALR |
0.21 |
0.011 |
— |
— |
— |
— |
Genomic‡ |
||||||
TP53 |
8.68 |
<0.0001 |
3.03 |
0.0003 |
1.21 |
0.784 |
High-risk |
3.24 |
0.0013 |
1.77 |
0.006 |
0.88 |
0.801 |
ASXL1-only |
2.45 |
0.063 |
1.17 |
0.579 |
1.22 |
0.767 |
The study demonstrated that mutations of TP53 and high-risk genes (including EZH2, SRSF2, IDH1, IDH2, U2AF1, CBL, NRAS, and KRAS) were adverse prognostic factors in MF. When the prognostic impact of each gene in the high-risk group was investigated, it showed that all genes were associated and improved the prognostic evaluation. CALR mutations were found to be associated with a lower risk of leukemic transformation. The study also showed that isolated mutations of ASXL1 had no prognostic value consistent with the findings from the validation cohort, and the impact on leukemic transformation was limited. However, when ASXL1 mutations were associated with the TP53 mutation or high-risk genes, they conversed a worse prognosis.
These results suggest that the exclusion of ASXL1 mutations from the prognostic classification of somatic mutations in MF may be discussed where high-risk mutations such as TP53, U2AF1, CBL, NRAS and KRAS may be included. The findings from this study warrant for a new molecular classification that will need to be validated in large multicenter cohorts.
References
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