1. ET vs. Prefibrotic myelofibrosis: Why does it matter
Tiziano BARBUI,MD Hematology and Research Foundation, Papa Giovanni XXIII Hospital Bergamo, Italy European Focus on Myeloproliferative Neoplasms and Myelodysplastic Syndromes 5-7 April 2013, Madrid, Spain

2. Distinguishing ET from PMF
WHO Classification
Distinguishing ET from PMF ET
“True ET”
“Prefibrotic
PMF”

3. Three important components to the process of developing classification of Hema Malignancies
First, use morphology, immunophenotype, genetic features, and clinical features to define diseases.
Second principle is that classification relies on building a consensus among as many experts as possible on the definition and nomenclature of the disease.
Third, while pathologists must take primary responsibility for developing a primary classification, involvement of clinicians is essential to ensure its usefulness and acceptance in daily practice.

4. Morphology in «true ET» and in prefibrotic myelofibrosis

5. ET and early PMF: different biology?
The molecular mechanisms underlying the development of histological features such as megakaryocyte clustering, are unclear.
The cellularity factor, correlates with whether the patient has the JAK2 V617 mutation (Wilkins et al Blood 2008;111:60-70)
JAK2V617F allele burden discriminates ET from early PMF (Hussein K et al.,Exp.Hematology 37,1186,2009)
About the molecular regulation of megakaryocyte location and clustering, it may be relevant that megakaryocyte clusters are observed in mice treated with SDF-1, the ligand for the CXCR4 receptor. (Avecill et al. Nat Med ;10:64-71)
Patients with pre-fibrotic PMF have a pattern of proplatelet formation similar to fibrotic PMF and different from that of «true» ET (Balduini A,PLoSOne, 2011)

6. Different presentation and outcomes?
Seven international centers
Inclusion criteria:
local ET diagnosis (from 1975 to 2008)
and pre-treatment Bone Marrow biopsy obtained at time of diagnosis (or within 1 year of diagnosis in untreated patients)
1,104 ET patients
WHO 2008 review by
WHO author (JT)
completely blinded to outcome data
True ET
PMF
Barbui et al, J Clin Oncol Aug 10;29(23):

7. Main characteristics at diagnosis
ET (n=891)
PMF (n=180)
P value
Age, years, median (range)
56 (13-91)
57 (21-88)
0.66
Male/Female
370/521
74/106
0.92
Follow-up, years
6.2 (0-27)
7.0 (0-27.2)
0.30
WBC, x 109/L, median (range)
8.6 ( )
9.7 ( )
< 0.001
Hb, g/dL, median (range)
14.1 ( )
13.8 ( )
0.01
PLT, x 109/L, median (range)
774 ( )
902 ( )
0.002
LDH (n=519), mU/mL median (range)
298 ( )
429 ( )
CD34+ (N=246) /mcL, median (range)
2 (0-15.2)
4.7 (0-60)
0.03
JAK2 (V617F)-pos (n=805)
422 (61%)
67 (58%)
0.56
Fibrosis (n=968)
23 (3%)
38 (22%)
Splenomegaly
146 (16%)
41 (23%)
0.04

8. Thrombosis Myelofibrosis Acute leukemia Survival
Disease complications during follow-up WHO ET: 6.2 yrs (range 0-27); WHO early prefibrotic PMF: 7 yrs (range 0-27)
Events
Thrombosis
Myelofibrosis
Acute leukemia
Survival
Barbui et al, JCO 2011

9. Thrombosis-free survival
0.00
0.25
0.50
0.75
1.00 5 10 15 20
Years from diagnosis
ET vs PMF ET
PMF
P-value = 0.69
Events
At risk
Barbui et al, JCO 2011

10. Does it matter to predict hematologic transformations?
Survival, Leukemic Transformation and Fibrotic Progression in Essential Thrombocythemia are significantly influenced by Accurate Morphologic Diagnosis
Incidence of AML OS
Incidence of MF
Barbui et al, J Clin Oncol Aug 10;29(23):

11. Barbui et al, JCO 2011 *EUROSTAT 2008
(crude death rates, all causes of death, EU 27 countries)
Barbui et al, JCO 2011

12. Survival in patients categorized by
different stages of primary myelofibrosis
Barosi et al, PlosOne 2012,7,4.

13. Three important components to the process of developing classification of Hema Malignancies
First, recognising that the underlying causes of the neoplasm are often unknown and may vary. So, we use morphology, immunophenotype, genetic features, and clinical features to define diseases.
Second principle is that classification relies on building a consensus among as many experts as possible on the definition and nomenclature of the disease.
Third, while pathologists must take primary responsibility for developing a primary classification, involvement of clinicians is essential to ensure its usefulness and acceptance in daily practice.

14. Poor reproducibility and debate on the nomenclature
Criticism to histopathology in early stage PMF and ET
Poor reproducibility and debate on the nomenclature
Morphological criteria are impaired by subjectivity their value in predicting clinical outcome is not yet consistently proven
In pathology, the typing and subtyping of most diseases should have a high degree of interobserver reliability and may be inadequate for routine clinical use
Classifications which cannot guarantee this reliability must be reconsidered.
Wilkins et al., Blood 2008; Brousseau et al Histopathology 2010; Buhr et al, Haematologica 2012;
Koopman et al,Am J Clin Pathol. 2011

15. Three important components to the process of developing classification of Hema Malignancies
First, recognising that the underlying causes of the neoplasm are often unknown and may vary. So, we use morphology, immunophenotype, genetic features, and clinical features to define diseases.
Second principle is that classification relies on building a consensus among as many experts as possible on the definition and nomenclature of the disease.
Third, while pathologists must take primary responsibility for developing a primary classification, involvement of clinicians is essential to ensure its usefulness and acceptance in daily practice.

16. Risk factors for thrombosis in ET (PVSG diagnosis)
Cox Multivariable Analysis HB
HCT
PLT
WBC
* Reference categories:
Bergamo centre; Females; Low risk factors; HB < 13 g/dL; HCT < 39.5 %; PLT < 650 (x109/L);
WBC <7.2 (x109/L); Absence of JAK2V617F
Carobbio et al, JCO 2008; Carobbio et al, Blodd 2008, Barbui et al, Blood 2009
Carobbio A et al., Blood 2007; JCO 2008 Barbui T et al,Blood 20010

17. PT-1 randomized clinical trial in high risk ET (Hydroxyurea+asa ) WCC & major hemorrhage p=0.01 WCC & thrombosis p=0.05 Plts & major hemorrhage p = Plts & thrombosis p= 0.4 (not significant)

18. RISK FACTORS FOR THROMBOSIS
in WHO-ET (n=891) (inception cohort)
Risk factor HR scores
Age >
CV risk factors
Previous thrombosis
JAK2 V617F
* Multivariate model adjusted for: sex, hemoglobin ,leukocyte and platelet counts, Hydroxyurea and aspirin use.
Score: low-risk
Score: intermediate risk
Score => high risk
Barbui et al, J Clin Oncol Aug 10;29(23): ; Barbui et al,Blood 2012.
Carobbio et al, Blood Jun 2;117(22): Epub 2011 Apr 13.

19. The IPSET thrombosis model in WHO-ET
LOW
INTERMEDIATE
HIGH
p=0.0001
Barbui et al, Blood 2012

20. Early prefibrotic PMF: Multivariate analysis (metric variables) for risk factors predicting fatal and nonfatal thrombotic events in the follow-up of 264 patients
Major thrombosis AT DVT
HR (95% CI) p HR (95% CI) p HR (95% CI) p
Female gender ( ) ( ) ( )
Age ( ) ( ) ( )
Prev. thrombosis ( ) ( ) ( )
Hb (higher) ( ) ( ) ( )
Plt count (higher) ( ) ( ) ( )
WBC (higher) ( ) ( ) ( )
JAK2 V617F ( ) ( ) ( )
CV risk factors ( ) ( ) ( )
Buxhofer et al., AJH ,2012

21. Hazard ratio (HR) for disease complications in patients treated
with Anagrelide (+ asa) vs Hydroxyurea (+asa) in PT1 trial
Bone marrow in PT1 trial
Fiber grade 0-1
135
Fiber grade 2
146
Fiber grade 3-4 80
Venous thromboembolism occurred less frequently in Anagrelide group (HR 0.27)

22. ANAHYDRET-Study vs. PT1-Trial PVSG-ET e.g. prefibrotic PMF and PMF1
Difference in the patient cohorts may explain the difference in study-results
ANAHYDRET-Study PT1-Trial
„true-ET“
PVSG-ET e.g. prefibrotic PMF and PMF1
Gisslinger et al, Blood Harrison et al, NEJM 1995

23. Bleeding is more frequent in early PMF and suggests caution on the use of aspirin in primary prophylaxis of thrombosis
ET (n=891)
PMF (n=180)
P value
Aspirin (%)
602 (68)
131 (73)
0.20
Bleeding in the follow-up, n (%)
55 (6)
21 (12)
0.009
Rate of bleeding (% pts/year)
0.79
1.39
Incidence Rate Ratio
1 (ref.)
1.76
0.039
Finazzi G, et al, Leukemia 2011

24. Multivariate analysis of risk factors for bleeding
HR (95% CI)
p-value
early/prefibrotic PMF
1.74 ( )
0.050
WBC ≥11 x109/L
1.74 ( )
0.041
Previous bleeding
2.35 ( )
0.025
Aspirin use
3.16 ( )
0.001
Finazzi et al,Leukemia 2011

25. PT-1 randomized clinical trial in high risk ET (Hydroxyurea+asa ) WCC & major hemorrhage p=0.01 WCC & thrombosis p=0.05 Plts & major hemorrhage p = Plts & thrombosis p= 0.4 (not significant)

26. Way does this distinction matter
WHO-ET vs. EARLY- PMF
Way does this distinction matter
Different clinico-hematological presentation
Different overall survival
Different myelofibrosis-free survival
Different leukemia-free survival
No difference in thrombosis-free survival,
but different risk factors for total thrombosis
Different risk of bleeding
There is a difference in the risk for thrombosis and bleeding

27. CONCLUSION :The limited reproducibility of this distinction precludes its use in clinical practice
Proposed solution: a scientific project, including the pathologists and hematologists
Aim
to select a small set of robust diagnostic criteria
to assess the reproducibility
to evaluate the corresponding clinical outcomes

28. ACKNOWLEDGEMENT