Impact of Early-Onset or Worsening Anemia in Patients with Myelofibrosis Treated with Ruxolitinib: A post hoc Analysis of the JUMP Study

Introduction: Anemia can influence decisions regarding initiation, dosing, and discontinuation of Janus kinase inhibitor therapy for myelofibrosis. We evaluated the impact of new-onset or worsening anemia following ruxolitinib initiation on spleen response, symptom severity, and overall survival in patients with myelofibrosis. Methods: This post hoc analysis used data from all patients enrolled in the phase 3b JUMP trial. Outcomes were stratified by presence or absence of new-onset or worsening anemia following ruxolitinib initiation, defined as hemoglobin decrease ≥15 g/L from baseline and hemoglobin <100 g/L (female)/<110 g/L (male) at Week 12, new transfusion requirement post-baseline until Week 12 (for baseline non-transfusion-dependent patients), or ≥50% increase from baseline in red blood cell transfusions through Week 12. Results: Overall, 2,233 patients were included; 52.9% developed new-onset or worsening anemia up to Week 12. Ruxolitinib was associated with improvements in spleen length and myelofibrosis symptoms, regardless of the presence or absence of new-onset or worsening anemia or baseline anemia status. No differences in spleen response or overall survival were observed between patients with versus without new-onset or worsening anemia, regardless of baseline anemia status. Conclusions: These results support the use of ruxolitinib in patients with myelofibrosis, regardless of baseline anemia or development of treatment-related anemia.