In both training and validation cohorts, patients with GLIM-defined malnutrition were significantly older (p < 0.001 and p = 0.004, respectively), had lower BMI (p < 0.001 and p < 0.001, respectively), lower preoperative serum albumin (Alb) (p < 0.001 and p < 0.001, respectively), and hemoglobin (Hb) (p < 0.001 and p < 0.001, respectively) levels. This evidence concerns the gene GSTM1 and malnutrition.