GSTM1 and anemia (phenotype): During treatment with darbepoetin alfa pre-existing anemia improved substantially, with patients experiencing a median increase in Hb of 0.9 g/dL between baseline and week 12; 57% of patients with Hb < 10 g/dL at baseline achieved Hb ≥ 10 g/dL and 46% of patients with Hb ≤ 11 g/dL at baseline achieved Hb > 11 g/dL at week 12.