Assessment of Sentinel Lymph Node Biopsy in Colon Cancer and Its Impact on Staging

Background: Missed nodal metastases during resection for colon cancer or missed occult metastases during pathological examination leads to down staging of the disease and increase the recurrence rate. The sentinel lymph node is a technique used to properly detect nodal metastases hence improving staging accuracy with subsequent proper application of adjuvant therapy. The aim of this study is to determine the feasibility of sentinel lymph node technique and its effect on staging of the disease. Methods: A total number of forty five patients with primary colon cancer (T1-3, any N, M0) were enrolled in the study. They were subjected to appropriate colonic resection based on the anatomic location of the tumor. A combined method of lymphatic mapping using technetium 99mTc -labeled sulfur colloid and patent blue was performed. After few minutes of injecting the tracers, the colon and its mesentery were examined for any blue-stained glands and areas of high radioactivity using a hand-held gamma probe. After colonic resection, the sentinel lymph node(s) and non-sentinel lymph nodes were sent for H&E staining. Positive sentinel lymph node(s) underwent no further analysis while negative nodes were submitted for immunohistochemical staining. Results: Sentinel lymph node(s) were successfully identified in 43 patients (95.6%) with a mean of 1.7 node/patient. The false negative rate is 7.1%, Sensitivity is 92.9%, specificity is 100%, negative predictive value is 88.2% and positive predictive value is 100%. Detailed focused examination using the immunohistochemical staining discovered 4 more positive patients who were supposed to be negative by the ordinary H&E staining resulting in upstaging rate of 9.3% among the whole study group and 21% among the negative-nodes patients. Conclusion: Sentinel lymph node mapping is a feasible technique with a relatively high identification rate. It can upstage some patients who will get benefit from further adjuvant chemotherapy resulting in reduced recurrence and better prognosis.