Abstract
In 2012, the International Working Group for Myeloproliferative Neoplasms (MPN) Research and Treatment (IWG-MRT) reported an associations between mild bone marrow (BM) fibrosis (⩾grade 1) in polycythemia vera (PV) and a lower incidence of thrombosis during the clinical course and a higher risk of fibrotic progression. The objective in the current study of 262 patients with PV was to validate these observations and also identify other risk factors for myelofibrosis-free survival (MFFS). About 127 (48%) patients displayed ⩾grade 1 reticulin fibrosis at the time of diagnosis; presenting clinical and laboratory features were not significantly different between patients with or without BM fibrosis. In univariate analysis, BM fibrosis had no significant impact on overall, leukemia-free or thrombosis-free survival, whereas a significant association was noted for MFFS (P=0.009, hazard ratio 2.9; 95% confidence interval 1.32–6.78); other risk factors for MFFS included leukocytosis ⩾15 × 109/l, presence of palpable splenomegaly and abnormal karyotype. During multivariable analysis, leukocytosis ⩾15 × 109/l, palpable splenomegaly and ⩾grade 1 BM reticulin fibrosis remained significant. The current study validates the previously observed association between ⩾grade 1 BM reticulin fibrosis in PV and subsequent fibrotic progression, and identifies leukocytosis and palpable splenomegaly as additional risk factors for fibrotic progression; additional studies are required to clarify the impact of BM fibrosis on thrombosis and that of abnormal karyotype on MFFS.
Highlights
Polycythemia Vera (PV) is a BCR-ABL1 negative myeloproliferative neoplasm (MPN) characterized by clonal erythrocytosis and a JAK2 mutation, either JAK2V617F or an exon 12 mutation, in 96% and 3% of cases, respectively.[1]
Thrombosis-free survival for 262 patients with Polycythemia Vera stratified by the presence of grade 1 or greater bone marrow reticulin fibrosis. 1 p=0.9 0.8
Other risk factors found to be prognostically significant for myelofibrosis-free survival (MFFS) in univariate analysis were leukocytosis ⩾ 15x109/l (P = 0.02, hazard ratio (HR) 2.8; 95% confidence interval (CI) 1.17–6.48), presence of palpable splenomegaly (P = 0.02, HR 2.6; 95% CI 1.14–6.08) and abnormal karyotype (P = 0.008, HR 6.3; 95% CI 1.62–24.84); on multivariable analysis, leukocytosis ⩾ 15 × 109/l (P = 0.04, HR 2.8; 95% CI 1.02– 7.62), presence of splenomegaly (P = 0.04, HR 2.4; 95% CI 1.02–5.8) and presence of bone marrow (BM) reticulin fibrosis (P = 0.02, HR 3.3; 95% CI 1.24–8.60) remained significant (Table 2)
Summary
Polycythemia Vera (PV) is a BCR-ABL1 negative myeloproliferative neoplasm (MPN) characterized by clonal erythrocytosis and a JAK2 mutation, either JAK2V617F or an exon 12 mutation, in 96% and 3% of cases, respectively.[1] Life expectancy in PV has been shown to be worse than that of the age- and sex- matched US population, with a median survival of 14 years and 24 years in patients younger than age 60 years.[2] Disease-related complications affecting survival in PV are thrombotic complications and disease progression into acute myeloid leukemia or myelofibrosis (MF).[3] Numerous prognostic factors have been identified as being involved in clinical phenotype, disease progression and survival of PV patients.
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