GSTM1 and esophageal squamous cell carcinoma: For ESCC with methylation index of 0.75–1.0, the best identified model included tobacco chewing, smoking, GSTM1 and GSTT1 null genotypes (OR = 11.37 [4.68–27.58], TBA = 0.75, TrBA = 0.76 CVC = 10/10).