Objectives: The current study identified patients with either essential thrombocythemia (ET) or polycythemia vera (PV) who have survived for at least 20 yr without the development of either acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) or myelofibrosis (MF) and compared their presenting features with those in whom these complications occurred in the first 10 yr of disease. Methods: The study patients were selected from an institutional database of 1061 patients with either ET (n = 603) or PV (n = 458). In both instances, three distinct groups were delineated and their presenting features compared; group A included patients who have remained AML/MDS/MF free after a minimum follow-up of 20 yr; groups B and C included patients who developed either AML/MDS or MF, respectively, in the first decade of their disease. Results: The respective number of patients who fulfilled the above-mentioned criteria for inclusion in groups A, B and C were 40, 12 and 8 for ET and 23, 18 and 12 for PV. In ET, compared with both groups B and C, group A displayed significantly fewer patients with less than normal hemoglobin level (P < 0.0001 and =0.02) or male sex (P = 0.005 and 0.05), respectively. On multivariable analysis, only anemia sustained its significance. A similar analysis in PV revealed an association between group B and leukocytosis using a leukocyte count threshold of either 10 or 15 × 109/L (P = 0.02). Conclusion: The current study identifies PV patients with leukocytosis and ET patients with anemia as the most likely to undergo leukemic or fibrotic transformation.
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