Ex vivo sentinel lymph node “mapping” in colorectal cancer

Background The purpose of this study was to evaluate the feasibility and reliability of ex vivo sentinel lymph node mapping in patients with colorectal cancer. Methods In the period January–June 2006, 44 consecutive patients underwent curative surgery for colorectal cancer. In patients with colon and rectal cancer, 0.5–2 ml of Patent Blue Dye was injected submucosally. The injection sites where then gently massaged for 5 min. Results In 96% of the patients with colon cancer and 94% of the patients with rectal cancer, at least one sentinel lymph node was found. There were no patients with a false negative sentinel node. The sensitivity was 100% with a negative predictive value of 100%. In 19% of the patients with colon cancer and 18% of the patients with rectal cancer the sentinel node was the exclusive site of lymph node metastases. After additional sectioning and staining, 7 of the 23 patients (30%) with a Dukes B colorectal cancer were upstaged. Conclusion The technique of ex vivo sentinel lymph node mapping is technically feasible with high sensitivity, high negative predictive value and a high rate of upstaging. The next step is to investigate, if detection of micro-metastases is associated with decreased survival and/or increased local recurrence rates.