Are ET and PV Patients Two Similar Populations As Concern Thrombotic Risk Factors?
Authors: Andriani Alessandro , Latagliata Roberto , Cedrone Michele , Di Veroli Ambra , Santoro Cristina , Spirito Francesca , Ruscio Carla , Crescenzi-Leonetti Sabrina , Porrini Raffaele , Di Giandomenico Jonny , Villivà Nicoletta , Spadea Antonio , Rago Angela , De Gregoris Cinzia , Cercola Paolo , Anaclerico Barbara , De Muro Marianna , Felici Stefano , Breccia Massimo , Montefusco Enrico , Bagnato Antonino , Cimino Giuseppe , Majolino Ignazio , Mazzucconi Maria Gabriella , Alimena Giuliana , Montanaro Marco 
Published: October 2019

Abstract
Thrombotic events are major complications in patients (pts) affected by Essential Thrombocytemia (ET) and Polycytemia Vera (PV). To compare thrombotic risk in these 2 groups, we evaluated retrospectively our database of 1249 ET and 623 PV pts diagnosed and followed in 11 hematological centers in the Latium region between 1/1980 and 12/2010: the diagnosis was done according to PVSG, WHO 2001 and 2008criteria based on the time of first observation. Baseline features of ET pts: 797F/452M,median age 62.9 yrs (range 19-96),median WBC count 8.8 x 109/L (range 1.2-57.7), median PLT count 812 x 109/L (range 457-3582), median Hb level 14.0 g/dl (range 6-20.5), JAK-2V617F positivity 59.7% with a median allele burden of 19,6% (range 0.2- 99.9), spleen enlargement in 18.7% of pts, previous thrombosis223/1239 evaluable pts (17.9%) [arterial 176/223 (14.1%), venous 47/223 (3.8%)]. Baseline features of PV pts: 289F/334M, median age 63.0yrs (range 21-91), median WBC count 10.1 x 109/L (range 3.5-37.6), median PLT count 457 x 109/L (range 169-1790), median Hb level 18.2 g/dl (range 10.5-24.8), JAK-2V617F positivity 94.3% with a median allele burden of 59.1% (range 0.3-99.9), spleen enlargement in 42% of patients, previous thrombosis 146/617 evaluable pts (23.7%)[arterial 114/617 (18.5%), venous 32/617 (5,2%)].in the ET cohort, after a median follow-up of 7.7 yrs, thrombotic complications were seen in 107/1141 evaluable pts (9.4%) [arterial60 (5.25%), venous 47 (4.11%)]; in the PV cohort, after a median follow-up of 8.5 yrs, thrombotic complications were seen in 107/623pts (17.2%) [arterial 67 (10.8%),venous 40 (6.4%)].All common risk factors for thrombosis were evaluated in multivariate analysis, searching the cut-off number for continuous variables with ROC curves. The significant variables at multivariate analysis for ET and PV pts are shown in the table; age, previous thromboses and spleen enlargement were risk factors in ET pts, while previous thromboses and JAK-2V617F allele burden were risk factors in PV pts. PLT count above ROC value seemed to be a protective factor in both cohorts. In conclusion, in contrast with the tendency to evaluate in a similar manner the thrombotic risk of PV and ET, data from our retrospective database showed that these 2 groups should be considered populations with different risk factors for thrombosis. Table 1.Putative prognostic factorsPolycythemia VeraEssential ThrombocythemiaHR95% C.I.pHR95% C.I .pPrevious thromboses2,311,13 - 4,740,021,871,08 -3,230,026Age ≥ 60 y1,540,79 - 2,990,211,901,18 - 3,060,009JAK2V617FPV: allelic burden ≥ 81% ET: pos1,951,03 - 3,710,040,760,48 - 1,210,25Plt countPV ≥ 452.109/L ET ≥ 944.109/L0,490,25 - 0,950,040,520,31 - 0,890,017Spleen enlargement0,670,34 -1,310,241,711,02 - 2,890,04CV risk factors (at least 1)0,920,41 - 2,030,830,870,51 - 1,490,62WBCPV ≥ 10,175.109/L ET ≥ 9,630.109/L1,090,57 - 2,080,801,410,89 -2,260,15

Disclosures
No relevant conflicts of interest to declare.