When we further stratified the digestive system cancer group into digestive tract and digestive gland cancer groups, results showed a significant association between allele A of MPO-463G > A and digestive gland cancer in all the genetic models (allele frequency model: OR = 0.63, 95%CI = 0.40–0.99; additive model: OR = 0.41, 95%CI = 0.23–0.73; recessive model: OR = 0.51, 95%CI = 0.29–0.89; dominant model: OR = 0.58, 95%CI = 0.35–0.96), digestive tract cancers in allele frequency model (OR = 0.75, 95%CI = 0.59–0.95), and dominant model (OR = 0.72, 95%CI = 0.56–0.92). The gene discussed is MPO; the disease is digestive system cancer.