DP128 | NEUTROPHIL-TO-LYMPHOCYTE RATIO AT DIAGNOSIS PREDICTS VENOUS THROMBOSIS IN PREFIBROTIC PRIMARY MYELOFIBROSIS: RESULTS FROM AN ITALIAN COOPERATIVE STUDY

Background: Primary myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, symptoms, cytopenias, and inflammation, and is classified into prefibrotic (prePMF) and overt stages. PrePMF carries a thrombotic risk comparable to that of essential thrombocythemia; however, few studies have specifically investigated the risk factors associated with thrombotic events (TEs) in this setting. The neutrophil-to-lymphocyte ratio (NLR), which reflects the imbalance between systemic inflammation and immune response, has emerged as a prognostic biomarker in a range of diseases, including hematological one. Aims: we evaluated the role of NLR as a predictor of TEs in prePMF patients (pts) enrolled in the INFLA-ME (INFLAmmation in MyeloproliferativE disease) retro-prospective, observational, cooperative study Methods: NLR was calculated at diagnosis as the ratio of the absolute neutrophil count (ANC) to the absolute lymphocyte count (ALC). Thrombosis-free survival (TFS) was defined as the time from prePMF diagnosis to the first thrombotic event. TFS was estimated using Kaplan-Meier analysis, and differences between groups were assessed with the log-rank test. Results: we enrolled 225 pts with a diagnosis of pre-PMF, revised according to the 2022 WHO criteria, between 1994 and 2023; 114 were male (50.7%). At diagnosis, median age was 61.7 (range 25-86) years. Most pts (86%) were classified as low or intermediate-1 risk according to the IPSS, and as high risk (58.7%) according to the IPSET-Thrombosis score. Splenomegaly was reported in 26 (11.6%) pts; 170 pts (75.6%) carried the JAK2 V617F mutation. TEs (69 in total) occurred in 67 pts (27.8%) before pre-PMF diagnosis. After a median follow-up of 5.9 years, a 37 TEs occurred in 31 pts (2.5 TEs/100pts/year; 18 arterial, 19 venous). In multivariate analysis, the risk of venous thrombosis was independently associated with history of previous venous TEs (HR = 4.46, p = 0.001) and NLR values ≥6 (HR 3.82, p=0.008). Pts with NLR ≥ 6 had a significantly shorter venous TFS (p=0.003, Figure 1). No significant association was found between NLR and the occurrence of total or arterial TEs Conclusion: the NLR is an inexpensive and readily available prognostic biomarker for venous thrombosis in prePMF pts. Integrating NLR assessment into conventional risk scores may improve the identification of pre-PMF pts who could benefit from cytoreductive therapy. Larger prospective studies are needed to validate these findings.