Patient distribution and outcomes on E4903 on the use of lenalidomide plus a prednisone taper in subjects with myelofibrosis. IWG-MRT spleen response⁸ : > 50% reduction in palpable component below the left costal margin (for spleen > 10 cm at baseline), complete absence of palpable component if < 10 cm at baseline. IWG-MRT anemia response⁸ : > 2 g/dL improvement in hemoglobin or becoming transfusion independent (if originally transfusion dependent).