Revised classification/ prognostication Myelofibrosis

RAYMOND WONG, MDHong Kong

• Consultant of the Department of Medicine & Therapeutics, Prince of Wales Hospital

• Dr. Wong received his medical degree from the Chinese University of Hong Kong and received his training in Haematology, Internal Medicine as well as Clinical Pharmacology and Therapeutics at the Prince of Wales Hospital, Hong Kong. He also obtained his Doctor of Medicine from the Chinese University of Hong Kong. He joined the Prince of Wales Hospital Poison Treatment Centre since its establishment in 2005 which is a tertiary referral centre for the management of patients with poisoning. Dr. Wong has published over 70 articles in peer-reviewed journals including Blood, Circulation, JAMA and the New England Journal of Medicine in various areas of haematology and therapeutics.

Myeloproliferative Neoplasms Revised Classification/Prognostication

Dr. Raymond SM Wong

Department of Medicine & Therapeutics

The Chinese University of Hong Kong

BTG 2015

Ph- Myeloproliferative Neoplasms (MPNs)

2008 WHO diagnostic criteria for Ph- MPNs

Diagnosis:

Both major + 1 minor OR

1st major + 2 minor

All 4 majors All 3 major + 2 minor

Incidence of JAK2 mutations

JAK2 V617F

JAK2 ex12

?

JAK2 V617F JAK2 V617F

PV ET MF

N Cross. Hematology Am Soc Hemat Educ Program 2011: 208-14

Alternative mechanisms of JAK2 activations

97% JAK2 V617F

2% JAK2 ex12

1% ?

60% JAK2 V617F

3% MPL ex10

3% SH2B3 (LNK)

34% ?

60% JAK2 V617F

5% MPL ex10

3% SH2B3 (LNK)

5% CBL

27% ?

PV ET MF

N Cross. Hematology Am Soc Hemat Educ Program 2011: 208-14

Calreticulin (CALR)

• In December 2013, two groups reported the occurrence of novel calreticulin (CALR) mutations in JAK2/MPL-unmutated PMF or ET

• CALR is a multi-functional Ca2+-binding protein chaperone mostly localized in the endoplasmic reticulum (ER)

• CALR is located on chromosome 19p13.2, contains 9 exons and its protein three domains

Ellgaard, L. & Helenius, A. Nature Reviews Molecular Cell Biology 4, 181–191 (2003)

Klampfl et al. NEJM 2013

Somatic Mutations of Calreticulin in MPNs

• Among patients with nonmutatedJAK2 or MPL, CALR mutations were detected in

• 67% of those with ET

• 88% of those with PMF

• A total of 36 types of insertions or deletions were identified: all cause a frameshift to the same alternative reading frame and generate a novel C-terminal peptide in the mutant calreticulin


CALR, compared with JAK2 mutations:

ET

• ↓ hemoglobin level

• ↓ leukocyte count

• ↑ platelet count

• ↓ risk of thrombosis

• Better survival (P = 0.04)

MF

• ↓ leukocyte count (P = 0.03)

• ↑ platelet count (P<0.001)

• Better survival (P<0.001)

P<0.001


The clinical course in patients with CALR mutation was more indolent than that in patients with the JAK2 V617F mutation

Nangalia J, et al. NEJM 2013

CALR Mutations According to Diagnosis




Somatic CALR Mutations in MPNs with Non-mutated JAK2

• In ET, an association between CALR mutations and

• higher platelet count

• lower hemoglobin level

• In addition, the study also suggested an increased incidence of fibrotic transformation in CALR-mutated ET without apparent survival difference


• 168 MPN patients (PV = 36, ET = 114, PMF = 18)

Ann Lab Med 2015;35:22-27

CALR Exon 9 Mutations in MPNs

• ET patients with CALR mutation had lower leukocyte counts and ages compared with JAK2-mutated ET patients

Ann Lab Med 2015;35:22-27

• 576 patients with WHO-defined ET

• In JAK2/MPL-unmutated cases, CALR mutational frequency was 49%

Blood. 2014;123(10):1552-1555

CALR+ JAK2 V617F+ MPL W515+ CALR, JAK2, MPL wt

% of patients 15.5% 64.1% 4.3% 16.1%

CALR+ vs JAK2 V617F+ CALR+ vs MPL W515+ CALR+ vs. triple negative

• Male• Younger age• Lower leukocyte count• Lower hemoglobin level• Higher platelet count

• Male • Male

CALR mutations in ET

• CALR-mutated and triple-negative cases displayed superior thrombosis-free survival

• CALR mutation had no impact on survival or transformation to post-ET myelofibrosis

Blood. 2014;123(10):1552-1555

Blood. 2014;123(10):1544-1551

JAK2 or CALR mutation in ET

• Compared with JAK2-mutated cases, CALR-mutated patients were:

• younger

• ↓ leukocyte count

• ↓ hemoglobin

• ↑ platelet count

Blood. 2014;123(10):1544-1551

JAK2 or CALR mutation in ET

CALR- vs JAK2-mutated patients

• No difference in OS, risk of leukemic or fibrotic transformation

• Better thrombosis-free survival

CALR exon 9 frameshift mutations in patients withthrombocytosis (not confirmed ET)

• In 289 patients referred for evaluation of persistent thrombocytosis

Chi J, et al. Leukemia 2014

CALR vs JAK2 vs MPL-mutated or triple-negative MF

• 254 MF patients who were cytogenetically characterized and screened for several MPN-characteristic mutations including ASXL1, EZH2, IDH and spliceosome mutations (SF3B1, SRSF2 and U2AF1)

• In JAK2/MPL-unmutated cases, CALR mutational frequency was 74%

• Patients with CALR mutations:

• younger


• lower DIPSS-plus score

• less likely to be anemic, require transfusions or display leukocytosis

Tefferi A, et al. Leukemia (2014) 28, 1472–1477

CALR+ JAK2 V617F+ MPL W515+ CALR, JAK2, MPL wt

% of patients 25% 58% 8% 9%

CALR vs JAK2 vs MPL-mutated or triple-negative MF• CALR mutations had a favorable survival

independent of DIPSS-plus risk and ASXL1 mutation status

• Triple-negative patients displayed inferior leukemia-free survival

• “CALR–ASXL1+” and “triple-negative” mutation profiles are prognosticallydetrimental

Tefferi A, et al. Leukemia (2014) 28, 1472–1477

CALR-mutated patients (vs. JAK2)

Essential Thrombocythemia

• younger age

• male sex

• higher platelet count,

• lower hemoglobin level

• lower leukocyte count

• lower incidence of thrombotic events

Primary Myelofibrosis

• younger


• better risk profile

• higher hemoglobin

• lower leukocyte count

• less spliceosome mutations

Tefferi A, et al. AJH 2015

Frequency of JAK2, CALR, and MPL mutations in MPNs

96%

3%

55% 65%

4%8%

15-24% 25-35%

Nanglia J and Green R, Hematology 2014; Tefferi A and Barbui T, AJH 2015

Diagnostic algorithm for BCR-ABL1-negative MPNs

• Genotyping for CALR could be a useful diagnostic tool for JAK2-or MPL-negative ET or PMF patients in conjunction with BM morphology

Tefferi A, et al. AJH 2015

Proposed Revised ET Diagnostic Criteria

2008 (Current) Proposed Revision

Tefferi A, et al. Leukemia 2014

All 4 major or first 3 major + 1 minorAll 4 major criteria

Proposed Revised MF Diagnostic Criteria



All 4 major or first 2 major + all minorAll 3 major criteria + 2 minor criteria

“Masked PV”

• JAK2-mutated patients who display PV-characteristic BM morphology but display hemoglobin levels 16-18.5 g/dl for men and 15-16.5 g/dl for women

Barbui T, et al. AJH 2013

A. Thrombosis-free survival

B. Myelofibrosis / leukemia-free survival

C. overall survival

in masked and overt PV

“Masked PV”

Proposed Revised PV Diagnostic Criteria



Both major + 1 minor1st major + 2 minor

All 3 major OR first 2 major + minor

Summary

• The molecular diagnostic gap in JAK2/MPL-unmutated ET/PMF is now partially addressed by the recent discovery of calreticulin (CALR) mutations in the majority of such cases

• Genotyping for CALR could be a useful diagnostic tool for JAK2-or MPL-negative ET or PMF patients. BM marrow morphology remains the central diagnostic platform

• CALR mutation may be a distinct disease group, with different clinical and hematological characteristics than that of JAK2-mutated patients

• Inclusion of CALR mutations in the WHO classification system for ET/PMF has been proposed

The End

Thank you

Education

Revised classification/ prognostication Myelofibrosis