GSTM1 and anemia (phenotype): Furthermore, a randomized study in preoperative patients with colon cancer (IVICA trial) compared oral iron and FCM, finding that IV iron did not reduce blood transfusions but was more effective than oral iron at treating preoperative anemia, with Hb increasing by 1.55 g/dL with FCM vs. 0.5 g/dL with oral iron (P < 0.001) [44].