Incidence of Early Thrombosis in Myeloproliferative Neoplasms (MPN): A Prospective Analysis from the Gruppo Laziale of Ph-Negative MPN

Background Thrombotic episodes are the major complication in the follow-up of Philadelphia negative Myeloproliferative Neoplasms (MPN), with high morbidity and mortality, as reported in several retrospective studies. At present, however, few prospective data are available on the early incidence of these complications.

Methods To address this issue, we report on 1087 patients [M/F 508/579, median age 67.6 years, interquartile range (IQR) 55.2 - 75.9] with newly diagnosed MPN enrolled in the prospective database of our regional cooperative group since January 2011. Of them, 571 (52.5%) had Essential Thrombocythemia (ET), 303 (27.9%) Polycythemia Vera (PV) and 213 (19.6%) Primary Myelofibrosis (PMF). The main clinical features at diagnosis of the whole cohort and according to the different MPNs are reported in the Table 1.

Results On the whole, 22 episodes of thrombotic complications were reported in 1087 patients (2.0%) at a median interval from diagnosis of 18.2 months (IQR 7.4 - 29.7): in particular, 15 (68.1%) were arterial (8 cerebral, 2 coronaric, 4 in the lower limbs, 1 splancnic) and 7 (31.9%) venous (5 in the lower limbs and 2 in the upper limbs). As to the incidence of early thrombosis in the different MPNs, they were 13/571 (2.2%) in ET patients, 5/303 (1.6%) in PV patients and 4/213 (1.8%) in PMF patients (p=0.810): median time from diagnosis to thrombotic event was also similar in the 3 MPNs (p=0.311). The 4-year cumulative Thrombosis-Free Survival (TFS) of the whole cohort was 97.3% (95%CI 96.0 - 98.6): there was no difference among the 3 MPNs as to 4-year TFS [96.7% (95%CI 94.8 - 98.6) in ET, 97.8% (95%CI 95.9 - 99.7) in PV and 98.7% (95%CI 96.9 - 100) in PMF, respectively, p=0.668). Several clinical features at diagnosis (age, gender, Hb levels, WBC and PLT counts, spleen enlargement, JAK-2 V617F mutation and previous thrombotic events) were evaluated for a role in predicting thrombotic events: only age (p=0.009) and previous thrombotic events (p=0.009) were significant.

Conclusions The incidence of early thrombosis seems low in the first 4 years after diagnosis of MPN based on our prospective database, without any difference among ET, PV and PMF: it is worth of note that only age and previous thrombotic events had a predictive role, thus confirming many retrospective reported data and reinforcing the prognostic value of old scoring system for thrombotic risk in MPN.

Table 1

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Table 1

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