[The risk factors for thrombosis, myelofibrosis and leukemia transformation in patients with polycythemia vera]

To reassess the natural history of polycythemia vera (PV) in Chinese and evaluate the relationship between the incidence of thrombosis, post-polycythaemic myelofibrosis with myeloid metaplasia( PPMM) , leukemia transformation and the therapeutic outcome and prognostic factors.

The clinical manifestations, laboratory parameters and treatment were retrospectively analyzed in 287 patients with PV. Univariate analysis of prognostic factors was performed using Log-rank model and multivariate analysis using COX model in term of the incidence of thrombosis, PPMM, hematologic or non hematologic cancers and mortality.

Of the 287 patients, the median follow-up time was 46 (8-360) months. 208 thromboses were recorded in 115 patients. Twice or more thrombotic events occurred on 59 patients (51.34%). Most of these episodes occurred either at presentation or in the 2 years before diagnosis. Elder patients, prior thrombosis, poor response to therapy were associated with poor prognosis. With these three adverse prognostic factors, the patients could be separated into different risk groups. The incidence of thrombosis was higher in high risk group. 36 patients progressed to PPMM, the median time to PPMM was 80 (7-190) months. Higher WBC count, splenomegaly and treatment with alkylating agent and hydroxy-carbamide (HU) were associated with poor prognosis. 2 cases progressed to AML. 1 to lymphoma and 1 to nonhematologic cancer. 13 patients died, the cause of death was fatal thrombosis in 9 and AML in 2.

The incidence of thromboembolism is higher and the time to myelofibrosis was shorter in Chinese PV patients than in western PV patients. The main factors that influence the survival of PV patients are thromboembolism and leukemia transformation.