Neutrophil-to-lymphocyte ratio half reduction as a surrogate of molecular response in polycythemia vera treated with ropeginterferon alfa-2b

Background: Polycythemia vera (PV) is a myeloproliferative neoplasm driven by JAK2 V617F mutations. Ropeginterferon alfa-2b effectively reduces both hematologic parameters and JAK2 allele burden, but molecular monitoring is not always readily available. Objectives: To evaluate whether a ⩾50% reduction in the neutrophil-to-lymphocyte ratio (NLR) can serve as a surrogate marker of hematologic and molecular response during ropeginterferon therapy. Design: Secondary analysis of a multicenter, phase II, open-label trial in South Korea. Methods: Ninety-five patients with PV received ropeginterferon alfa-2b biweekly for 48 weeks. NLR and JAK2 allele burden were serially measured, and generalized estimating equations and logistic regression were used to assess associations. Results: NLR half reduction significantly predicted hematologic response (week 24 OR 6.42, p = 0.001) and molecular response consistently across all time points (week 24 OR 27.94, p < 0.001). Conclusion: NLR half reduction is a simple, cost-effective biomarker that may reflect molecular response and treatment efficacy in PV.