Lymph Node Recovery from Colorectal Tumor Specimens:Recommendation for a Minimum Number of Lymph Nodes to be Examined

Lymph node involvement is the mostimportant prognostic factor for patients who have undergone radicalsurgery for colorectal carcinoma. An accurate examination of thesurgical specimens is mandatory for the correct assessment of the lymphnode status of the tumor. The risk of understaging is particularly highfor patients with tumors classified as Dukes B (TNM stage II). The aimof this study was to determine if a specified minimum number of lymphnodes examined per surgical specimen could have any effect on theprognosis of patients who had undergone radical surgery for Dukes Bcolorectal cancer. Between 1988 and 1995 a total of 140 patientsunderwent radical resection of Dukes B colorectal cancer by the samesurgeon (C.C.). The relation between clinicopathologic variables andsurvival was estimated using the Kaplan-Meier method. The Coxproportional hazard regression model was used to identify the variablesthat can independently influence survival. A median of 12 lymph nodes(range 3–38) was examined per tumor specimen. The 5-year survival rateof Dukes B patients who had had eight or fewer lymph nodes examinedafter surgery was 54.9%, whereas the survival rate for those who hadhad nine or more lymph nodes examined was 79.9% (p < 0.001). Cox regression analysis identified the number of lymph nodes asthe only independent prognostic factor (p = 0.01).Seventy patients with one to four metastatic lymph nodes (Dukes Cpatients) who had been operated on during the same period were includedin the survival analysis for comparison. The 5-year survival rate ofthe Dukes B patients with eight or fewer lymph nodes examined wassimilar to that of the 70 Dukes C patients (54.9% and 51.8%,respectively). Examination of eight or fewer lymph nodes in Dukes Bcolorectal patients may be considered a high risk factor for missingpositive lymph nodes in the surgical specimens. Our results suggestthat harvesting and examining a minimum of nine lymph nodes persurgical specimen may be sufficient for reliable staging of lymphnode-negative tumors.