GSTM1 and anemia (phenotype): Although treatment of cancer-associated anemia with ESAs increases Hb levels, which may modulate the efficacy of cancer radiotherapy by improving tumor oxygenation and reducing tumor HIF-1α expression [109, 110], and ESAs treatment prior to chemotherapy improves chemotherapeutic outcomes by mediating the prevention of anemia, tumor hypoxia, and increased drug delivery [111], the risks of ESAs have been widely reported.