Although epoetin and darbepoetin alfa treatment of such patients increases hemoglobin, reduces transfusion requirements, relieves symptoms of anemia, and improves health-related quality of life [5–8], the efficacy is less than that in the nephrology setting with hemoglobin responses (defined as an increase in Hb > 20 g/L, or Hb increased to 120 g/L or more) typically about 60% [6, 9–11]. The gene discussed is GSTM1; the disease is anemia (phenotype).