ObjectiveTo evaluate clinical value of colon leakage score (CLS), a preoperative predictive scoring system, for risk of anastomotic leakage after left-sided colorectal cancer surgery. MethodsThe clinical data of 310 patients who underwent left-sided colorectal cancer surgery from January 2010 to December 2014 were studied retrospectively. Risk factors for postoperative anastomotic leakage were analyzed by univariate analysis. The sensitivity and specificity of CLS system were determined by receiver operating characteristic (ROC) curve analysis. Resultsa total of 14 patients were diagnosed as anastomotic leakage. The point of CLS for the patients with anastomotic leakage was significantly higher than that for the patients without anastomotic leakage (14.21±5.76 versus 4.43±3.36, t=9.474, P=0.000). The results of ROC curve analysis showed that the sensitivity and specificity of the CLS system were 92.9% and 88.6%, respectively. The area under the curve was 0.957 (95% CI 0.924-0.991). The best cut off value of CLS was 10 (The Youden index was 0.867). The results of univariate analysis showed that the age, preoperative hemoglobin level, status of intestinal obstruction, and blood loss were associated with postoperative anastomotic leakage (P<0.05). ConclusionThe preoperative predictive score system CLS could accurately predict occurrence of anastomotic leakage. While large, multicenter prospective randomized controlled trial is still needed to further confirm it.