Neutrophil to lymphocyte ratio at diagnosis predicts venous thrombosis in prefibrotic primary myelofibrosis: results from a multicenter cooperative study

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by splenomegaly, symptoms, cytopenias, and chronic inflammation. PMF has two stages: pre-fibrotic (prePMF) and overt PMF. PrePMF and essential thrombocythemia share a similar high thrombotic risk, but few studies have examined thrombosis risk factors in prePMF. The neutrophil-to-lymphocyte ratio (NLR), reflecting the imbalance between systemic inflammation and immunity, has emerged as a prognostic biomarker in various diseases. We investigated the predictive value of NLR for thrombotic risk in a multicenter cohort of 225 prePMF patients enrolled in the retro-prospective observational INFLA-ME (INFLAmmation in MyeloproliferativE disease) cooperative study. After a median follow-up of 5.9 years, 37 thrombotic events occurred in 31 patients (2.5 events/100 patients/year; 18 arterial, 19 venous). Multivariate analysis linked venous thrombosis risk to prior venous events (HR 4.46, p = 0.001) and NLR ≥ 6 (HR 3.82, p = 0.008). The patients with NLR ≥ 6 showed a shorter venous thrombosis-free survival (p = 0.003). NLR value had no significant association with total and arterial thrombotic events. In conclusion, NLR is an inexpensive and accessible prognostic biomarker of venous thrombosis in prePMF. The integration of NLR into conventional risk scores may allow for better identification of pre-PMF patients requiring cytoreduction.