Relation of serum sTfR to Hb levels in patients with leukemia studied at time of diagnosis, n = 21 (A) or during intensive CT, n = 23 (B) and in patients with solid tumor at diagnosis, n = 21 (C), or during intensive CT, n = 30 (D). Solid lines represent the regression lines computed in each group of patients. Dashed lines depict the regression line and the 95% confidence limits of the control population showing an appropriate stimulation of erythropoiesis by the anemia.