GSTM1 and anemia: Patients aged 18 or older diagnosed with colon adenocarcinoma located at least 15 cm from the anal margin who were scheduled for elective curative surgery.Iron deficiency anemia was defined using WHO criteria: Hemoglobin (Hb) <13 g/dl in men, Hb <12 g/dl in women, serum ferritin <30 ng/ml, and transferrin saturation index <20%.The study did not restrict the surgical methods used, allowing for laparoscopy, open surgery, single port, and other approaches