GSTM1 and colorectal carcinoma: Keeler et al. 2017 [31] reported a median increase in Hb of 1.55 g/dL (IQR; 0.93–2.58) in patients with CRC who received 1000 mg or 1500 mg of parenteral FCM at least 14 days prior to surgery compared to an increase of 0.5 g/dL (IQR; -0.13–1.33) in patients who received oral ferrous sulfate twice daily until surgery (p<0.001).