If platelets are not a prognostic factor in ET, what is? Carles Besses Hospital del Mar–IMIM, Barcelona

Factors associated with risk of vascular complications in ET patients Host factors Advanced age History of thrombosis Cardiovascular risk factors ET-specific factors Thrombocytosis Leukocytosis Mutations (JAK2 V617F, CALR) MPN-associated prothrombotic state

Main points Thrombocytosis as a risk factor for vascular complications Other factors associated with thrombotic risk Clinical assessment of thrombotic risk How to deal with thrombocytosis in ET patients

Thrombocytosis and risk of vascular complications in ET An unpredictable connection? What the studies say?

Extreme thrombocytosis is associated with bleeding diathesis Study Patients no. Risk factor for bleeding Platelet count at diagnosis P Fenaux et al.1 147 >2000x109/L <0.02 Bellucci et al.2 94 >1000x109/L <0.01 Alvarez-Larrán et al.3 # 300 >800x109/L Palandri 4 565 0.003 #patients <60 years 1 Cancer 1990;66:549 2 Cancer 1986;58:2440 3 Blood 2010;116:1205 4 Br J Haematol 2012;156:281 van Genderen & Michiels, Presse Med 1994;23:73

The level of the platelet count per se does not correlate with thrombotic incidence or symptoms at diagnosis Lengfelder et al, Br J Haematol 1998;100:15

Thrombocytosis at diagnosis is not a predictive factor for thrombosis Patients no. Risk factors for thrombosis (RR or P) Age >60 Previous thrombosis Platelet count Leukocytosis CRF Cortelazzo et al. (1990) 100 10.3 (2.05-51.5) 13 (4.1-41.5) NS ─ Colombi et al. (1991) 103 P<0.001 Besses et al. (1999) 148 3.3 (1.5-7.4) 3.0 (1.5-6.0) 4.7 (1.8-11.8) Bazzan et al. (1999) 187 NS (>55) Jantunen et al. (2001) 132 P=0.01 Wolanskyj et al. (2006) 322 1.51 (1.05-2.18) 2.3 (1.25-4.24)1 1.74 (1.15-2.66)2 Carobbio et al. (2007) 439 2.3 (1.3-3.9)3 2.3 (1.4-3.9)4 Passamonti et al. (2008) 605 P=0.03 Carobbio et al. (2008) 657 2.1 (1.2-3.4)3 3.0 (1.3-6.9)5 Girodon et al. (2010) 311 P<0.05 Palandri et al. (2011) 532 2.2 (1.07-4.85)3 1.76 (1.95-2.97)6 Campbell (2012) 776 Montanaro et al. (2014) 1144 2.36 (1.48-3.79) 2.98 (1.07-8.32) CRF: cardiovascular risk factors; 1arterial only; 2WBC ≥15x109/L; 3age >60 and previous thrombosis evaluated together; 4WBC ≥8.7x109/L; 5WBC ≥10.4x109/L; 6WBC ≥11x109/L;

Thrombocytosis at diagnosis is not a predictive factor for thrombosis Patients no. Risk factors for thrombosis (RR or P) Age >60 Previous thrombosis Platelet count Leukocytosis CRF Cortelazzo et al. (1990) 100 10.3 (2.05-51.5) 13 (4.1-41.5) NS ─ Colombi et al. (1991) 103 P<0.001 Besses et al. (1999) 148 3.3 (1.5-7.4) 3.0 (1.5-6.0) 4.7 (1.8-11.8) Bazzan et al. (1999) 187 NS (>55) Jantunen et al. (2001) 132 P=0.01 Wolanskyj et al. (2006) 322 1.51 (1.05-2.18) 2.3 (1.25-4.24)1 1.74 (1.15-2.66)2 Carobbio et al. (2007) 439 2.3 (1.3-3.9)3 2.3 (1.4-3.9)4 Passamonti et al. (2008) 605 P=0.03 Carobbio et al. (2008) 657 2.1 (1.2-3.4)3 3.0 (1.3-6.9)5 Girodon et al. (2010) 311 P<0.05 Palandri et al. (2011) 532 2.2 (1.07-4.85)3 1.76 (1.95-2.97)6 Campbell (2012) 776 Montanaro et al. (2014) 1144 2.36 (1.48-3.79) 2.98 (1.07-8.32) CRF: cardiovascular risk factors; 1arterial only; 2WBC ≥15x109/L; 3age >60 and previous thrombosis evaluated together; 4WBC ≥8.7x109/L; 5WBC ≥10.4x109/L; 6WBC ≥11x109/L;

Correlation of thrombocytosis and leukocytosis with vascular complications during cytoreductive treatment in ET patients Author Patient no. Cytoreductive drug Thrombosis Bleeding Cortelazzo et al.1 100 Busulfan Platelet count <600x109/L for <70% of follow-up (P<0.025) Carobbio et al.2 416 HU ± ASA Platelet count <400x109/L (P=0.95) WBC >10x109/L (P<0.015) Hernández-Boluda et al.3 166 Patients in mantained CR according ELN criteria (2009) (P=0.8)* Campbell et al.4 776 HU + ASA AG + ASA Platelet count >450x109/L (P=0.4) High WBC (P=0.03) Platelet count >450x109/L (P=0.001) High WBC (P=0.01) Hernández-Boluda et al.5 154 AG ± ASA Patients in mantained CR according ELN criteria (2009) (P=0.59)# Patients in mantained CR according ELN criteria (2009) (P=0.23)Δ 1J Clin Oncol 1990;8:556; 2Blood 2010;116:1051; 3Br J Haematol 2011;152:81; 4Blood 2012;120:1409; 5Ann Hematol 2013;92:771 *cumulative incidence of thrombosis, #incidence rate of major thrombosis, Δincidence rate of major bleeding HU: hydroxyurea, AG: anagrelide, ASA: acetylsalycilic acid

Risk of major bleeding in the PT-1 cohort according to platelet counts during follow-up Campbell et al, Blood 2012;120:1409

Main points Thrombocytosis as a risk factor for vascular complications Other factors associated with thrombotic risk Clinical assessment of thrombotic risk How to deal with thrombocytosis in ET patients

Leukocytosis at diagnosis: controversial results Patients no. Risk factors for thrombosis (RR or P) Age >60 Previous thrombosis Platelet count Leukocytosis CRF Cortelazzo et al. (1990) 100 10.3 (2.05-51.5) 13 (4.1-41.5) NS ─ Colombi et al. (1991) 103 P<0.001 Besses et al. (1999) 148 3.3 (1.5-7.4) 3.0 (1.5-6.0) 4.7 (1.8-11.8) Bazzan et al. (1999) 187 NS (>55) Jantunen et al. (2001) 132 P=0.01 Wolanskyj et al. (2006) 322 1.51 (1.05-2.18) 2.3 (1.25-4.24)1 1.74 (1.15-2.66)2 Carobbio et al. (2007) 439 2.3 (1.3-3.9)3 2.3 (1.4-3.9)4 Passamonti et al. (2008) 605 P=0.03 Carobbio et al. (2008) 657 2.1 (1.2-3.4)3 3.0 (1.3-6.9)5 Girodon et al. (2010) 311 P<0.05 Palandri et al. (2011) 532 2.2 (1.07-4.85)3 1.76 (1.95-2.97)6 Campbell (2012) 776 Montanaro et al. (2014) 1144 2.36 (1.48-3.79) 2.98 (1.07-8.32) CRF: cardiovascular risk factors; 1arterial only; 2WBC ≥15x109/L; 3age >60 and previous thrombosis evaluated together; 4WBC ≥8.7x109/L; 5WBC ≥10.4x109/L; 6WBC ≥11x109/L;

Leucocytosis and thrombocytosis at diagnosis as risk factors for vascular complications in 891 WHO-defined ET patients Bleeding Arterial thrombosis Venous thrombosis Finazzi et al 1* Higher risk WBC ≥11x109/L HR: 1.74 (1.02-2.97) P=0.04 No increased risk PLT ≥800, ≥1000, ≥1200, ≥1500, ≥2000x109/L Carobbio et al 2 WBC ≥11x109/LΔ HR: 1.66 (1.01-2.72) P=0.044 Lower risk PLT>1000x109/L# HR: 0.42 (0.22-0.78) P=0.007 Male sex HR: 1.99 (1.03-3.83) P=0.039) 1Leukemia 2012;26:716; 2Blood 2011;117:5857 *Including early-PMF patients; #in the entire study population and in JAK2V617F-positive patients; Δnot significant when retricted to JAK2V617F-positive patiens

Hematologic and clinical features at diagnosis of 214 ET patients Age, years, median (range) 64 (9-93) Sex (male/female) 57/157 Splenomegaly, no. (%) 15 (7) Cardiovascular risk factors, no. (%) 116 (54.5) Hemoglobin, g/L, 140 (82-167) WBC count, x109/L, >10x109/L, no. (%) 8.6 (4.4-23.7) 63 (29.9) Platelet count, x109/L, ≥1000x109/L, no. (%) ≥1500x109/L, no. (%) 691 (450-2814) 36 (16.8) 7 (3.3) Angona et al, Med Clin (Barc) (in press)

Thrombosis-free survival of 214 ET patients according to initial WBC count 62% at 10 years 86% at 10 years WBC  10x109/L WBC > 10x109/L Median follow-up 6.9 years (0-27) Angona et al, Med Clin (Barc) (in press)

JAK2 V617F mutation and clinical outcomes in ET patients Author Patients no. Overall risk of thrombosis Arterial thrombosis Venous thrombosis Thrombosis at presentation Evolution to PV Ziakas1 2905 1.84 (1.40-2.43) 1.96 (1.43-2.67) 2.09 (1.44-3.05) 1.88 (1.38-2.56) ─ Dahabreh et al 2 2436 1.83 (1.32-2.53) 1.68 (1.31-2.15) 2.50 (1.71-3.66) 2.05 (1.53-2.74) 7.67 (2.04-28.87) Lussana et al 3 3150 1.92 (1.45-2.53) 1.77 (1.29-2.43) 2.49 (1.71-3.61) 1Haematologica 2008;93:1412; 2Leuk Res 2009;33:67; 3Thromb Res 2009;124:409 Results are expressed in Odds Ratios and 95% CI

Chao & Gotlib, Blood 2014;123:1438 Professional illustration by Debra T, Dartez

CALR-mutated ET A distinct disease entity from JAK2V617F-mutated ET CALR-mutated vs JAK2V617F-mutated Younger age Higher number of male patients Higher platelet count Lower risk of thrombosis Lower hemoglobin level Lower WBC count Higher serum erythropoietin level No difference in major bleeding No polycythemic transformation Higher mutant allele burden No difference in the risk of MF transformation No difference in the risk of AL transformation Higher number of patients in low-risk group (classical and IPSET) No difference in overall survival* Clinical/Biological Phenotype Clinical Outcomes Rumi et al, Blood 2014;123:1544 Rotunno et al, Blood 2014;123:1552 * Longer overall survival according to Klampfl et al, N Engl J Med 2013;369:2379

ET CALR-pos: 10 cases per 1000 person - years Cumulative incidence of thrombotic events in patients with CALR mutated ET, JAK2 mutated ET and PV ET CALR-pos: 10 cases per 1000 person - years ET JAK2-pos: 25 cases per 1000 person - years PV: 30 cases per 1000 person - years P=0.001 P=0.314 Rumi et al, Blood 2014;123:1544

Vannucchi & Guglielmelli, Semin Thromb Hemost 2013;39:496

Main points Thrombocytosis as a risk factor for vascular complications Other factors associated with thrombotic risk Clinical assessment of thrombotic risk How to deal with thrombocytosis in ET patients

Risk factors for thrombosis (RR or P) Advanced age and previous thrombosis at diagnosis as predictive factors for thrombosis Patients no. Risk factors for thrombosis (RR or P) Age >60 Previous thrombosis Platelet count Leukocytosis CRF Cortelazzo et al. (1990) 100 10.3 (2.05-51.5) 13 (4.1-41.5) NS ─ Colombi et al. (1991) 103 P<0.001 Besses et al. (1999) 148 3.3 (1.5-7.4) 3.0 (1.5-6.0) 4.7 (1.8-11.8) Bazzan et al. (1999) 187 NS (>55) Jantunen et al. (2001) 132 P=0.01 Wolanskyj et al. (2006) 322 1.51 (1.05-2.18) 2.3 (1.25-4.24)1 1.74 (1.15-2.66)2 Carobbio et al. (2007) 439 2.3 (1.3-3.9)3 2.3 (1.4-3.9)4 Passamonti et al. (2008) 605 P=0.03 Carobbio et al. (2008) 657 2.1 (1.2-3.4)3 3.0 (1.3-6.9)5 Girodon et al. (2010) 311 P<0.05 Palandri et al. (2011) 532 2.2 (1.07-4.85)3 1.76 (1.95-2.97)6 Campbell (2012) 776 Montanaro et al. (2014) 1144 2.36 (1.48-3.79) 2.98 (1.07-8.32) CRF: cardiovascular risk factors; 1arterial only; 2WBC ≥15x109/L; 3age >60 and previous thrombosis evaluated together; 4WBC ≥8.7x109/L; 5WBC ≥10.4x109/L; 6WBC ≥11x109/L;

Conventional risk stratification in ET patients Low-risk Age 60 years No history of thrombosis Platelet count <1500x109/L High-risk Age >60 years* History of thrombosis* Platelet count 1500x109/L† * High-risk of thrombosis; † High-risk of bleeding modified from Cervantes, Hematology Am Soc Hematol Educ Program 2011:215

International Prognostic Score for ET IPSET IPSET-survival* Age ≥60 years Leukocyte count ≥11x109/L History of thrombosis : 2 points : 1 point IPSET-thrombosis* Age >60 years History of thrombosis Cardiovascular risk factors JAK2V617F : 1 point : 2 points Score Median survival Low-risk Intermediate High-risk 1-2 ≥3 not reached 24.5 years 13.8 years Score Thrombosis risk (patients/year) Low-risk Intermediate High-risk <2 2 >2 1.03% 2.35% 3.56% * based on 867 WHO-defined ET patients * based on 891 WHO-defined ET patients Passamonti et al, Blood 2012;120:1197 Barbui et al, Blood 2012;120:5128

International Prognostic Score for ET IPSET IPSET-survival* Age ≥60 years Leukocyte count ≥11x109/L History of thrombosis : 2 points : 1 point IPSET-thrombosis* Age >60 years History of thrombosis Cardiovascular risk factors JAK2V617F : 1 point : 2 points Score Median survival Low-risk Intermediate High-risk 1-2 ≥3 not reached 24.5 years 13.8 years Score Thrombosis risk (patients/year) Low-risk Intermediate High-risk <2 2 >2 1.03% 2.35% 3.56% * based on 867 WHO-defined ET patients * based on 891 WHO-defined ET patients Passamonti et al, Blood 2012;120:1197 Barbui et al, Blood 2012;120:5128

Main points Thrombocytosis as a risk factor for vascular complications Other factors associated with thrombotic risk Clinical assessment of thrombotic risk How to deal with thrombocytosis in ET patients

Treatment targets of cytoreductive therapy in ET Clinical setting Platelet count <400x109/L <600x109/L History of thrombosis and/or major bleeding Intolerance to cytoreductive drugs Leukocyte count (normal) No consensus Leukocytosis in the setting of thrombosis? bleeding?

Control of cardiovascular risk factors (CRF) Management of ET HIGH RISK LOW RISK Age ≥60 years History of thrombosis/ serious hemorrhage Thrombocytosis >1500x109/L Age <60 years No history of thrombosis/ serious hemorrhage Control of cardiovascular risk factors (CRF) JAK2V617F-negative AND no CRF JAK2V617F-positive OR CRF First-line therapy Second-line therapy Resistance Thrombosis2 Hemorrhage3 MD not responding to ASA Hydroxyurea1 + Low-dose ASA Watch & Wait Low-dose ASA Anagrelide Interferon alfa-2 Intolerance Microvascular disturbances (MD) Special situations Pregnancy  Interferon alfa-2 Very elderly  Busulphan 1 use with caution if <40 years 2 oral anticoagulation in venous thrombosis 3 ASA contraindicated

General recommendations in the treatment of ET patients Follow the policy of risk-adapted therapy Preferentially use non-leukemogenic drugs as first-line therapy in high-risk young patients Avoid alkylating agents after hydroxyurea exposure Use acetylsalycilic acid on an individual basis Do not treat pediatric patients with cytoreductive drugs unless it is absolutely necessary Include patients in clinical trials

Take-home messages In most ET patients the degree of thrombocytosis per se should not be the only criterion to start cytoreductive therapy Risk stratification is the best strategy to decide when to treat or not a patient WHO-defined ET diagnosis is essential to assess risk of vascular complications and survival The role of CALR mutations in the current treatment approach of ET patients has to be defined