Our research has the following advantages: (1) Independent analysis of the association between preoperative anemia in esophageal cancer patients with the radical disease and LOS; (2) Independent analysis of the relationship between preoperative Hb in patients with esophageal cancer radical disease and LOS; (3) Enough variables were adjusted to avoid the influence of confounding factors on the research results; (4) The results were trustworthy and steady, with little missing data. The gene discussed is GSTM1; the disease is anemia (phenotype).