Results of a retrospective study of patients with essential thrombocythemia (ET) and polycythemia vera (PV) showed an association between the presence of splenomegaly at diagnosis and an increased risk of thrombosis or cardiovascular events, as well as an increased risk of death. The findings from this study were published in Hematology Reports.1
Of the Philadelphia-negative MPNs, primary myelofibrosis (PF), ET, and PV, enlargement of the spleen is considered to be common in the setting of PF, and progressive splenomegaly has been shown to have deleterious effects on quality of life in these patients. In contrast, the frequency and clinical ramifications of an enlarged spleen in patients with ET and PV have been less well characterized, although palpable splenomegaly has been previously shown to be associated with an increased risk of venous thrombosis in patients with PV.2
Of note, at the present time, none of the major prognostic models for patients with Philadelphia-negative MPNs include spleen size as a prognostic factor for survival.
Of the 238 patients with ET and 165 patients with PV included in this single-center study, the respective median ages at diagnosis were 65.92 years and 62.28 years. JAK2 V617F positivity was observed in 72.26% and 94.54% of patients with ET and PV, respectively.
At diagnosis, splenomegaly (defined as minimum longitudinal diameter was 15 cm at echotomography of computed tomography) was found in 15.54% of patients with ET and 38.18% of patients with PV. Interestingly, splenomegaly was more common in men than women; it was present in 24% of men and 11.65% of women with ET, while 45.71% of men and 24.19% of women with PV were found to have splenomegaly at diagnosis.
A key finding of this study was a significant association between splenomegaly and the risk of thrombosis or cardiovascular events for patients with ET and PV. Specifically, the frequency of thrombosis or cardiovascular events for patients with ET and splenomegaly was 39.87% compared with 24.37% for those without splenomegaly (P =.04). Similarly, in the setting of PV, this rate was 44.44% in those with splenomegaly compared with 30.39% for patients without spleen enlargement (P =.02).
At a median follow-up of 45.96 months for patients with ET and 58.42 months for those with PV, the death rate was significantly higher for those with ET characterized by splenomegaly (32.43%) compared to those without splenomegaly (8.42%; P =.0001). Corresponding results for patients with PV were 22.22% versus 7.84% (P <.004).
In their concluding remarks, the study authors stated that they believe that “the prognostic value of splenomegaly is underestimated in ET and PV,” and that “well designed clinical studies are needed to evaluate the significance of splenomegaly in ET and PV patients and its impact on OS and on thrombotic risk.”
1. Accurso V, Santoro M, Raso S, et al. Splenomegaly impacts prognosis in essential thrombocythemia and polycythemia vera: A single center study. Hematol Rep. 2019;11:8281. doi:10.4081/hr.2019.8281
2. Cerquozzi S, Barraco D, Lasho T, et al. Risk factors for arterial versus venous thrombosis in polycythemia vera: a single center experience in 587 patients. Blood Cancer J. 2017;7:662.