Poster Session I: Myeloproliferative neoplasms - Clinical
Polycythemia Vera (PV) is a myeloproliferative neoplasm mainly affecting median advanced age while rarely occurs in young patients. PV natural history is marked by vascular complications and studies exploring the thrombotic events and their management in young PV patient are lacking.
The purpose of the present study is to evaluate the natural history and in particular arterial thrombotic complications in young patients with PV.
We selected from our database 203 consecutive patients (103 males, 100 females; mean age at diagnosis 60 ± 15.6 y; median follow-up 7.48 y - range 0.02 - 43.5) diagnosed with PV between 1969 and 2018. All diagnoses were performed or revised according to WHO 2016 criteria. Patients have been stratified according to age at diagnosis in “Youngs”, with an age at diagnosis ≤ 45 y (n = 41, 20.2%) and “Old”, with an age at diagnosis > 45 y (n = 162, 79.8%). For all patients the presence of at least one cardiovascular risk factor (CVRF) (smoking habit, hypertension, diabetes and dyslipidemia) and all thrombotic events were recorded. All patients were treated with low dose aspirin, phlebotomies to maintain hematocrit below 45% and cytoreduction when indicated. Statistical analysis was performed using the χ2 test or Fisher's exact, Kaplan Meyer (KM) method for survival curves and the Cox regression model for multivariate analysis.
CVRF are more frequent in Old (68 % vs 49% in Youngs; p = 0,027). Follow-up was significantly longer (13.6 y range 0.7-43.5 vs 6.5 y range 0.02-29.2, p <0.001) in Youngs that display also a better overall survival (p < 0.001). 7 out of 41 (17%) Youngs and 34 out of 162 Old (21%) suffered for an arterial thrombotic event (p = NS). In 5 (12%) and 14 (8%) respectively, arterial thrombosis occurred at diagnosis, therefore being the patients not treated. In contrast, respectively in 2 (5%) and 20 (12%) patients arterial thrombosis occurred during follow up (p = NS). Youngs display a significant longer arterial thrombosis free survival (p = 0.015) compared to old patients. Old age at diagnosis is confirmed as an independent risk factor for arterial thrombosis during follow-up also in Cox regression model adjusted for CVRF (Figure 1; p = 0,04; HR 7,93; CI95% 1,05-59,76).
The young patients here evaluated are one fifth of all PV patients, in agreement with other few available data of the literature. Not surprisingly, the CVRF were more common in old than in young patients and Youngs have a longer overall survival. We failed to recognize a significant difference in the incidence of arterial thrombosis in different ages and we think that this is due to the small number of young patients. However, it seems that old age per se represents a risk factor for arterial thrombotic risk, meaning that a patient diagnosed before the age of 45, treated appropriately since youth and strictly managed, has less endothelial damage compared to an older patient.
Strengths of this study are the diagnosis obtained in agreement with WHO 2016 criteria in all PV patients, the long duration of follow-up in a single center that allowed the estimation of the risk of thrombosis, and the management in all cases in agreement with best clinical practice guidelines. Among the limitations, there is the retrospective design of the study that impose caution on the interpretation of results. Larger and prospective studies are needed to confirm and clarify our findings.