Validation of sentinel node mapping in patients with colon cancer

Background Sentinel lymph node (SLN) mapping techniques have been validated in breast cancer and melanoma. This study summarizes our experience with SLN mapping for colon cancer. Methods Fifty-five patients with colon cancer underwent intraoperative SLN mapping. One mL of 1% isosulfan blue was injected subserosally around the tumor. The first nodes highlighted with blue were identified as the SLNs. SLNs underwent multiple sectioning and immunohistochemical staining for cytokeratin. The overall learning curve was calculated. Results Lymphatic mapping adequately identified at least 1 SLN in 45 patients (82%). SLNs adequately predicted regional status in 44 of 45 (98%) cases. In 9 of 45 cases (20%), the SLNs were the only sites of metastases. Among the 14 cases that were SLN positive, 6 of 55 patients (11%) were positive only by immunohistochemistry. Of the 31 cases with negative SLNs, 1 case had a 3.5-mm pericolonic tumor-replaced non-SLN (3% false-negative rate). The overall learning curve stabilized after five cases. Conclusions Intraoperative SLN mapping is a feasible technique, with a quick learning curve, and had a reasonable SLN identification rate. Negative SLNs accurately predict the status of non-SLNs 97% of the time. Eleven percent of patients were upstaged by demonstration of micrometastases and may benefit from adjuvant chemotherapy.