The Relationship Between the Resected Colon Length and the Number of Lymph Nodes in Colorectal Cancer: A Retrospective Cohort Study

Objective: The prognostic factors that are important for colorectal cancer are the pathological grade of the tumor and the existence of lymph node involvement. Currently, the curative treatment option is resection of the tumor with adequate length and margin along with complete dissection of lymph nodes draining the site of resection. Our study investigated into retrieving adequate lymph nodes for accurate staging as well as the relationship between lymph nodes and colon and rectum specimen length. Methods: This retrospective cross-sectional study examined the correlation between resected colon length and lymph node count in patients with colorectal cancer diagnosed between January 2010 and June 2018. We defined a cutoff value for the segment length to be resected to allow adequate staging of the tumor. Furthermore, we examined the relationship between the resected segment lengths and survival. Results: Of the patients who were included in this study, 211 were men and 169 were women. The mean resected colon length was 26.47 +/- 17.09 cm and the mean dissected lymph node count was 29.05 +/- 20.84. There was a positive correlation between specimen length and total lymph node count as well as specimen length and the existence of reactive lymph nodes that were statistically significant (r=0.319, p=0.001; r=0.312, p=0.001, respectively). In our study, tumor localization was described in three regions: the right colon, left colon and rectum. The mean right colon region specimen length was 28.8 +/- 15.5 cm, while it was 22.0 +/- 11.0 cm for the left colon region, and 21.7 +/- 10.6 cm for the rectum region. The 5-year overall survival rate was 53.2%, whereas the 5-year disease-specific survival rate was 58.2%. Conclusion: The mean specimen length to achieve the cutoff value for adequate lymph node retrieval (least 12 lymph nodes) was 16 cm in our study (ROC curve, AUC=0.689 +/- 0.05, p=0.001). The resected colon length and the number of retrieved lymph nodes were positively correlated in our study. Based on this confirmation, a cutoff value of 16 cm was calculated to achieve an adequate segment length to be resected.