Calleja et al. [36] reported a greater increase in Hb in patients with colon cancer who received IV FCM (median dose of 1000 mg given 28.5 days preoperatively) compared to patients who received varying doses and formulations of oral iron (1.5 g/dL vs. 0.5 g/dL; p<0.0001) between diagnosis of anemia and hospital admission for surgery, and between diagnosis and 30 days postoperatively (3.1 g/dL vs. 1.5 g/dL; p<0.0001). This evidence concerns the gene GSTM1 and anemia (phenotype).