GSTM1 and anemia (phenotype): When comparing the laboratory results (Table S2), it becomes clear that, despite similar iron parameters between groups, in the nontreated ID-group, fewer patients had preoperative anemia, with a mean Hb level at the outpatient clinic of 13.5 g/dL (versus 10.8 g/dL in the IVIS-group, p < 0.001) and 13.0 g/dL at admission (versus 11.8 g/dL in the IVIS-group, p = 0.002).