The role of sentinel lymph node mapping in staging of colon and rectal cancer

Nodal metastasis is the best predictor of survival for patients with colon cancer. Statistical models based on random distribution of positive lymph nodes suggest that to correctly classify nodal status with 95 percent confidence, 20 nodes are needed for T1 lesions, 17 nodes for T2, and 15 nodes for T3. The mean number of nodes identified in American patients is 8, suggesting that they might not be accurately staged. Patients in our tumor registry staged as "node-negative" had a short survival when they had < or =10 lymph nodes evaluated when compared with patients with >10 lymph nodes evaluated (p < 0.01). We hypothesized that the use of sentinel lymph node may assist in the staging of colon cancer.

Thirty-eight consecutive patients with colon lesions were prospectively enrolled into this trial between February 1998 and November 1999. Thirty-one patients met criteria for analysis. During surgery, Lymphazurin blue dye was injected subserosally into the area around the tumor. Routine nodal evaluation, with extra cuts of all sentinel nodes, was undertaken.

At least one sentinel lymph node was found in 18 of 31 patients (58 percent). Sensitivity of 67 percent, specificity and positive predictive value of 100 percent, and negative predictive value of 94 percent were found when sentinel lymph nodes were identified. In 2 of these 18 patients, the sentinel lymph node was the only positive lymph node found.

Application of the sentinel lymph node technique to colon cancer may make it easier to identify lymph nodes most likely to contain metastatic disease, potentially "down-staging" more patients. This may have implications in postoperative care.