Effect of Red Blood Cell Transfusion Dependence on the Natural History of Myeloproliferative Neoplasm-Associated Myelofibrosis.

BACKGROUND: There are 2 widely used criteria for red blood cell (RBC) transfusion dependence in persons with myeloproliferative neoplasm (MPN)-associated myelofibrosis: (1) the International Working Group-Myelofibrosis Research and Therapy (IWG-MRT) criteria (receipt of 2 U RBC in the preceding month); and (2) the Rand-Delphi definition (2 U RBC per month averaged over 3 months). We studied effect of these criteria on survival and risk of leukemic transformation in 259 subjects with MPN-associated myelofibrosis. PATIENTS AND METHODS: On the basis of hemoglobin (Hb) and transfusion history, subjects were assigned to 1 of the 4 cohorts: (1) Hb ≥ 100 g/L (n = 136; 52%) and no RBC transfusions in the preceding 4 months; (2) Hb < 100 g/L, and no RBC transfusions in the preceding 4 months (n = 56; 22%); (3) subjects who met IWG-MRT criteria, but not the Rand-Delphi criteria for RBC transfusion dependence (n = 34; 13%); and (4) subjects who met the Rand-Delphi criteria for RBC transfusion dependence (n = 33; 13%). RESULTS: Three-year probability of survival among the 4 cohorts was 81% (95% confidence interval [CI], 71-87), 55% (95% CI, 36-71), 52% (95% CI, 31-69), and 47% (95% CI, 24-67), respectively (P = .0005). There was no significant difference in baseline characteristics or survival between cohorts 3 and 4 and they were combined for subsequent analyses. In multivariate analyses, subjects who met either definition of RBC transfusion dependence had significantly worse survival (hazard ratio, 2.61; 95% CI, 1.38-4.96; P = .01). CONCLUSION: RBC transfusion dependence is associated with worse survival irrespective of definition of transfusion dependence. No effect of anemia or RBC transfusion dependence on leukemic transformation was observed.