GSTM1 and anemia: The WHO definition of anemia (< 13 g/dL in men and < 12 g/dL in women), which is different with that in China (< 12 g/dL in men and < 11 g/dL in women) adopted in this study, is derived from the distribution of Hb values in epidemiologic investigations and not by the clinical and physiological impact of those values [40, 41], thereby it may influence the results of a long-term survival following CRC surgery.